Swarm M138 Modem Product Manual 1.41 User Guide

: June 3, 2024
: SWARM

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Swarm M138 Modem Product Manual 1.41
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Swarm M138 Modem Product Manual 1.41

Swarm M138 Modem
PRODUCT MANUAL
Revision 1.41 · August 2022 © 2022 Swarm Technologies, Inc.

Legal Notices
This User Manual provides user information and is provided “as is.” Swarm Technologies and its affiliated companies, directors, officers, employees, agents, trustees or consultants (“Swarm”) assume no responsibility for any typographical, technical, content or other inaccuracies in this User Manual. Swarm reserves the right to revise this User Manual or withdraw it at any time without prior notice. You can find the current version of this Swarm Modem User Manual at www.swarm.space.
SWARM MAKES NO GUARANTEES, CONDITIONS, WARRANTIES, OR REPRESENTATIONS, EITHER EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION, ANY IMPLIED REPRESENTATIONS, GUARANTEES, CONDITIONS OR WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, NONINFRINGEMENT, SATISFACTORY QUALITY, NON-INTERFERENCE, ACCURACY OF INFORMATIONAL CONTENT, OR ARISING FROM A COURSE OF DEALING, LAW, USAGE, OR TRADE PRACTICE, USE, OR RELATED TO THE PERFORMANCE OR NONPERFORMANCE OF ANY PRODUCTS, ACCESSORIES, FACILITIES, SERVICES OR USER INFORMATION, EXCEPT AS EXPRESSLY STATED IN THE LIMITED WARRANTY. ANY OTHER STANDARDS OF PERFORMANCE, GUARANTEES, CONDITIONS AND WARRANTIES ARE HEREBY EXPRESSLY EXCLUDED AND DISCLAIMED TO THE FULLEST EXTENT PERMITTED BY LAW. THIS DISCLAIMER AND EXCLUSION SHALL APPLY EVEN IF THE EXPRESS LIMITED WARRANTY PROVIDED IN THE LEGAL INFORMATION BOOKLET FAILS OF ITS ESSENTIAL PURPOSE. FURTHER, THE LIMITED WARRANTY COVERS THE SWARM M138 MODEM (INCLUDING HARDWARE, SOFTWARE AND/OR FIRMWARE) AND ACCESSORIES ONLY, AND NO WARRANTY IS MADE AS TO USER INFORMATION AND/ OR COVERAGE, AVAILABILITY OR GRADE OF SERVICE PROVIDED BY SWARM SEPARATELY FOR SWARM SATELLITE SERVICES.
IN NO EVENT SHALL SWARM BE LIABLE, WHETHER IN CONTRACT OR TORT OR ANY OTHER LEGAL THEORY, INCLUDING WITHOUT LIMITATION STRICT LIABILITY, GROSS NEGLIGENCE OR NEGLIGENCE, OR IMPLIED WARRANTY, FOR ANY DAMAGES IN EXCESS OF THE PURCHASE PRICE OF THE SWARM M138 MODEM (INCLUDING HARDWARE, SOFTWARE AND/OR FIRMWARE) AND/OR ACCESSORIES AND/OR THE COST OF SWARM SATELLITE SERVICES PROVIDED, NOR SHALL SWARM BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, CONSEQUENTIAL, OR PUNITIVE DAMAGES OF ANY KIND, OR LOSS OF REVENUE OR PROFITS, LOSS OF BUSINESS, LOSS OF PRIVACY, LOSS OF USE, LOSS OF TIME OR INCONVENIENCE, LOSS OF INFORMATION OR DATA, SOFTWARE OR APPLICATIONS OR OTHER FINANCIAL LOSS CAUSED BY THE SWARM MODEM-M138 (INCLUDING HARDWARE, SOFTWARE AND/ OR FIRMWARE) AND/OR ACCESSORIES AND/OR THE SWARM SATELLITE SERVICES, OR ARISING OUT OF OR IN CONNECTION WITH THE ABILITY OR INABILITY TO USE THE SWARM MODEM-M138 (INCLUDING HARDWARE, SOFTWARE AND/OR FIRMWARE) AND/OR ACCESSORIES AND/OR THE SWARM SATELLITE SERVICES , TO THE FULLEST EXTENT THESE DAMAGES MAY BE DISCLAIMED BY LAW AND REGARDLESS OF WHETHER SWARM WAS ADVISED OF THE POSSIBILITIES OF SUCH DAMAGES.

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Third Party Information This User Manual might refer to third party sources of information, hardware or software, products or services and/or third party web sites (“third party information”). Swarm does not control, and is not responsible for, any third party information, including without limitation the content, accuracy, copyright compliance, compatibility, performance, trustworthiness, legality, decency, links, or any other aspect of third party information. The inclusion of such third party information does not imply endorsement by Swarm of the third party information. ANY THIRD PARTY INFORMATION THAT IS PROVIDED WITH SWARM’S FACILITIES, SERVICES, PRODUCTS OR USER INFORMATION IS PROVIDED “AS IS.” SWARM MAKES NO REPRESENTATIONS, GUARANTEES OR WARRANTIES IN RELATION TO THIRD PARTY INFORMATION AND SWARM SHALL NOT BE LIABLE FOR ANY LOSSES, DAMAGES, LIABILITIES, JUDGMENTS, FINES, AMOUNTS PAID IN SETTLEMENT, EXPENSES OR COSTS OF DEFENSE SUSTAINED IN RELATION TO ANY SUCH THIRD PARTY INFORMATION.
Intellectual Property, Trade Secret, Proprietary or Copyrighted Information To protect Swarm proprietary and confidential information and/or trade secrets, this User Manual may describe some aspects of Swarm technology in generalized terms. Swarm products may include copyrighted Swarm and third party software. Any such copyrighted software contained in Swarm products may not be modified, reverse engineered, distributed or reproduced in any manner to the extent provided by law. The purchase of any Swarm products shall not be deemed to grant either directly or by implication or otherwise, any license under copyrights, patents, or patent applications of Swarm or any third party software provider, except for the normal, nonexclusive, royalty free license to use that arises by operation of law in the sale of a product.
Content Copyright You are exclusively responsible for the use of the Swarm Modem-M138, including proper use of third party copyrighted materials. If you violate these terms you agree to defend, indemnify and hold Swarm harmless with respect to any claims or actions by third parties related to your improper use of copyrighted materials and to pay all costs, damages, fines and other amounts incurred by Swarm, or on its behalf, in the defense of any such claims or actions.
Export Compliance The Swarm Modem-M138 is controlled by the export laws and regulations of the United States of America. The U.S. Government may restrict the export or re-export of this product to certain individuals and/or destinations. For further information, contact the U.S. Department of Commerce, Bureau of Industry and Security or visit www.bis.doc.gov

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Revision History

Revision Date

Comment

Firmware Version

1.00 11/11/21 Swarm M138 Modem Product Manual – Initial Release

1.01 12/01/21 Corrected pinout table Updated $GN and $GS descriptions Updated Modem status message structure Updated date/time format to reflect YYYY-MM- DDTHH:MM:SS
1.02 12/07/21 Updated Table 6 to reflect Figure 4

1.10 01/12/22 Updated transmit current measurements Removed section 3.3 Updated T/R pin notes Updated $GP command description Updated M138 Modem images Updated regulatory information

1.11 01/20/22 Added antenna guidance to Section 6

1.20 02/15/22 Updated power characteristics for all M138 operating modes 2.0.0 Updated RSSI_bkgnd operating range Updated GPIO1 mode description GPS Cold/Warm start flowchart and timings 1pps pin removed $MT L=U command option removed Updated capacitance and inductance table

1.30 05/26/22 $MT L=U and $MM L=U command options added Updated GPS Antenna Guidance Updated capacitance and inductance table

2.0.2

1.31 06/27/22 Updated Section 1.4 Updated Section 6.2.1

1.40 07/21/22 Updated Section 1.4 Updated $MT and $MM command sections

2.0.3

1.41 08/01/22 Added ANATEL certification to Section 1

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Additional Resources:
Please visit our developer tools webpage for quickstart guides and other helpful resources: https://swarm.space/documentation-swarm

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Revision History

Additional Resources:

1 Safety Information and Compliance

1.1 FCC Compliance

1.2 ISED Compliance

1.3 RF Exposure Guidance

1.4 EU RED Certification

1.5 ANATEL Certification

1.6 Transceiver Regulatory Certification

2 Product Overview

3 Mechanical Specification

3.1 Modem Dimensions

3.2 Environmental

4 Electrical Interfaces

4.1 User Host Device

4.2 Modem Pin Allocation

4.3 DC Power Interface

4.4 Power On/Off Control

4.5 Serial Data Interface

4.6 LED Indicators

5 Design Guidance

5.1 Input Connections

5.2 Decoupling and Feed-through Capacitors

5.3 Input Voltage Examples

5.4 Communications

5.4.1 Level Shifting

5.5 Example Power Regulation Design

6 RF Interfaces

6.1 RF Connectors

6.2 RF Antenna

6.2.1 Antenna Characteristics

6.2.2 Ground Plane Requirements

6.3 Antenna Debugging

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7 Software interface

Message types

General command structure

Command timing

Command responses

Boot-up sequence

GPS Date/Time Reference

Messages

Table of Commands and Messages

$CS – Configuration Settings

$DT – Date/Time Status

$FV – Firmware Version Read

$GJ – GPS Jamming/Spoofing Indication

$GN – Geospatial Information

$GP – GPIO1 Control/Status

$GS – GPS Fix Quality

$MM – Messages Received Management (2-way operation)

$MT – Messages to Transmit Management

$PO – Power Off

$PW – Power Status

$RD – Receive Data Unsolicited Message

$RS – Restart Device

$RT – Receive Test

$SL – Sleep mode

$M138 – Modem Status Unsolicited Message

$TD – Transmit data

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1 Safety Information and Compliance
The Swarm M138 Modem is designed to comply with the standards for Radio Emissions Compliance and Electromagnetic Compatibility in the United States, Canada, Australia, New Zealand, United Kingdom, European Union, Brazil, as well as worldwide.
1.1 FCC Compliance
1.1.1 FCC Interference Statement (Part 15.105 (b))
This equipment has been tested and found to comply with the limits for a Class B digital device, pursuant to Part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference in a residential installation. This equipment generates, uses, and can radiate radio frequency energy and, if not installed and used in accordance with the instructions, may cause harmful interference to radio communications. However, there is no guarantee that interference will not occur in a particular installation. If this equipment does cause harmful interference to radio or television reception, which can be determined by turning the equipment off and on, the user is encouraged to try to correct the interference by one of the following measures:
Reorient or relocate the receiving antenna. Increase the separation between the equipment and receiver. Connect the equipment into an outlet on a circuit different from that to which the receiver
is connected. Consult the dealer or an experienced radio/TV technician for help.
This device complies with part 15 of the FCC Rules. Operation is subject to the condition that this device does not cause harmful interference.
1.1.2 FCC Part 15 Clause 15.21:
Changes or modifications not expressly approved by the party responsible for compliance could void the user’s authority to operate the equipment.
1.1.3 FCC Part 15.19(a):
This device complies with part 15 of the FCC Rules. Operation is subject to the following two conditions: (1) This device may not cause harmful interference, and (2) this device must accept any interference received, including interference that may cause undesired operation.

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1.1.4 FCC ID:
The FCC ID for the Swarm M138 Modem is 2AVE9-M138. All manufacturers integrating the Swarm M138 Modem into their products are required to provide a physical or e-label stating “Contains FCC ID: 2AVE9-M138”.
1.1.5 Part 15 Subpart B Disclaimer:
The final host product requires Part 15B compliance testing with the modular transmitter installed.
1.2 ISED Compliance
1.2.1 ISED RSS-Gen Notice CAN ICES-3 (B)NMB-3(B):
This device complies with Industry Canada’s license-exempt RSSs. Operation is subject to the following two conditions: (1) This device may not cause interference; and (2) This device must accept any interference, including interference that may cause undesired operation of the device.
Le présent appareil est conforme aux CNR d’Industrie Canada applicables aux appareils radio exempts de licence. L’exploitation est autorisée aux deux conditions suivantes : 1) l’appareil ne doit pas produire de brouillage; 2) l’appareil doit accepter tout brouillage radioélectrique subi, même si le brouillage est susceptible d’en compromettre le fonctionnement.
1.2.2 IC ID:
The IC ID for the Swarm M138 Modem is 25817-M138. All manufacturers integrating the Swarm M138 Modem into their products are required to provide a physical or e-label stating “Contains IC ID: 25817-M138”.
1.3 RF Exposure Guidance
In order to comply with FCC / ISED RF Exposure requirements, this device and antenna must be installed to provide at least 36 cm separation from the human body at all times.
Afin de se conformer aux exigences d’exposition RF FCC / ISED, cet appareil doit être installé pour fournir au moins 36 cm de séparation du corps humain en tout temps.

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1.4 EU RED Certification
1.4.1 EU Declaration of Conformity: NB01 107350 0008 Rev. 00
1.4.2 Article 10(2)/(10):
This product has been so constructed that the product complies with the requirement of Article 10(2) as it can be operated in at least one Member State as examined and the product is compliant with Article 10(10) as it has no restrictions on putting into service in all EU member states.
1.5 ANATEL Certification
The ANATEL ID for the Swarm M138 Modem is 12172-22-13638. All manufacturers integrating the Swarm M138 Modem into their products are required to provide a physical or e-label stating “Contains ANATEL ID: 12172-22-13638”.

1.6 Transceiver Regulatory Certification
The Swarm Modem is a regulatory approved modular transmitter that is designed to be integrated into an enclosed host system. With appropriate external connections, the host can be designed to meet full regulatory tests and sold as a regulatory certified product that meets FCC, IC, and CE requirements. Table 1 below is a partial list of regulatory approvals.

Regulatory Approvals
FCC

Radio Tests

EMC Tests

FCC CFR47 Parts 2, 15, and 25

Safety Tests

Industry Canada RSS170 Issue 2 – March 2011

ETSI EN 301 721 CISPR 16-23:2010/A1:2010

V2.1.1 (2016-05)

EN 55032:2012

EN 6100-4-2/EN55024:2010

ETSI EG203 367 EN 6100-4-3/EN55024:2010

V1.1.1

EN 6100-4-8/EN55024:2010

Table 1: Overview of the Swarm M138 Modem regulatory approvals.

EN 62368-1:2014/A11:2017

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2 Product Overview

The Swarm (Model: M138) satellite data modem transmits and receives data to and from Swarm’s space network and is designed to be embedded into a third- party product. Swarm backend systems support the delivery of customer data via a REST API or Webhook to the cloud service of each user’s choice.
The Swarm Modem is a module suitable for a variety of low-bandwidth use cases: from connecting people and tracking vehicles, ships, or packages to relaying sensor data for agriculture, energy, and industrial IoT applications.
The Swarm Modem is a Mini-PCI Express Card that can be easily integrated into any new or existing PCB design. The Swarm Modem communicates via a standard 3.3V CMOS serial UART interface or a PC interface with a USB-to-serial converter.

Category
Components
Onboard Sensors Dimensions and Mass Power

Description
GPS, VHF radio with integrated T/R switch, U.FL connector for GPS and VHF antenna, indicator LEDs, 3.3V serial interface, 3.3V GPIO uBLOX GPS (lat/lon/alt), CPU Temperature
51.0 mm x 30.0 mm x 5.3 mm, 9.6 g See detailed description in the Mechanical Specification section.

Mode
Sleep Receiver Active Transmitter On

Typical

3.3V

–

26mA

25mA

850mA 550mA

Peak

3.3V

80A

110A

40mA 1000mA

45mA 600mA

Protocol

Modified NMEA two-letter command set

Bit rate

1 kbps. Maximum packet size is 192 bytes

Table 2: Overview of the Swarm Modem.

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3 Mechanical Specification

3.1 Modem Dimensions
The overall dimensions of the Modem and its weight are summarized below.

Parameter Length Width Height Weight
Table 3: Modem Mechanical Dimensions and Weight.

Value 51.0 mm 30.0 mm 5.3 ±0.1 mm 9.6 g

Figure 1: Modem front and back views.

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3.2 Environmental

The environmental specifications of the Modem are summarized below. The Swarm Modem is not conformally coated, and as such the user needs to provide any weatherproofing for their application.

Parameter Operating Temperature Range Storage Temperature Range Operating Humidity Range Storage Humidity Range
Table 4: Environmental Specifications.

Value -40 °C to +85 °C -40 °C to +85 °C 0% to 95%, non-condensing 0% to 95%, non-condensing

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4 Electrical Interfaces
The following subsections contain information for the electrical interfaces of the Modem.
4.1 User Host Device
The user host device provides the following connections to the Modem:
DC power supply input: 3.0V to 5.0V, (1000 mApeak at 3.3V) EMI/RFI shielding CAN is required if using a switching DC power supply in order to contain radiated emissions Additional filtering of the power supply is highly recommended See Design Guidance for best practices
Data interface 3.3V Serial Data Interface
Satellite signal (Use the provided U.FL connector labeled VHF) GPS signal (Use the provided U.FL connector labeled GPS) GPIO1 (optional)

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4.2 Modem Pin Allocation
The pin numbering scheme of the Swarm Modem is shown in Figure 4. All pins are located on the card edge of the Swarm Modem and are designed to fit in a standard mPCIE card connector. The pin function assignment is given in Tables 6 and 7. Multiple supply grounds are provided and all power pins / supply grounds are required to be connected to the power supply in order to limit the current on any one pin. Multiple signal grounds are provided to reduce cross- talk. Many pins are intentionally left empty, and must be left unconnected.

Figure 4: Modem pinout and pin number

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Pin Number

Name

Type

Description

1,3,5-8,10,12, 14,16,19-20, 22-25,28,30-33, 36,38,44-49, 51
2,39,41,52

NC VDD

NC Power

4,9,15,18,21,26, 27,29,34,35,37, 40,43,50
11
13
17

GND
UART_RX UART_TX T/R OUTPUT

Ground
Comms Comms Digital Output

GPIO1

Digital

Input

Table 6: Modem pin numbers and descriptions.

Output/Analog

Additional Notes Pin Number Note

No Connection

3.3V/5V at up to 1000mA/600mA
Ground

3.3V serial receive

3.3V serial transmit

Transmit/Receive indicator *leave unconnected if not used

General input/output

purpose

Connection is unbuffered and connected directly to a GPIO on the Modem

processor. Configuration will be provided via serial commands. GPIO1 pin

is 3.3V tolerant and open drain, with a sink current limit of 8 mA (20 mA

with a relaxed VOL/VOH)

2, 39, 41, 52

The VDD connection points are in parallel with one another and power the Modem. If the designer wants to enable a complete power off mode, a load switch can be provided here

HIGH when transmitting

LOW when receiving

The state will not change faster than 500s prior to the Modem beginning

to transmit and 500s after the Modem has finished transmitting.

*leave open if not used

Table 7: Additional notes on pin numbers.

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4.3 DC Power Interface
The DC power interface consists of the DC power inputs as summarized below. The power requirements apply to DC power measured at the Swarm Modem user connector input and not at the output of the power supply. It is required that users incorporate the required bypass capacitors for the supplied power input as can be seen in Design Guidance.

Name

Description

Min Typ

Max Unit

VCC

Module supply voltage

3.00 3.30

VCC Ripple Module supply voltage ripple

–

VCC Limits Module supply voltage absolute limits

3.00 –

Current consumption – Sleep Mode

–

Current consumption – Receiver Active

Current consumption – GPS Acquisition Mode* 40

ICC (3.3V) Current consumption – Transmitter on

750 850

Current consumption – Sleep Mode

–

Current consumption – Receiver Active

Current consumption – GPS Acquisition Mode* 40

ICC (4.2V) Current consumption – Transmitter on

640 700

Current consumption – Sleep Mode

–

Current consumption – Receiver Active

Current consumption – GPS Acquisition Mode* 40

ICC (5.0V) Current consumption – Transmitter on

500 550

Table 8: Power supply characteristics for 3.3, 4.2, and 5.0V supplies to the Modem.

5.00 75 5.00 80 40 55 1000 100 40 55 800 110 45 55 600

V mVpp V A mA mA mA A mA mA mA A mA mA mA

*Includes satellite receiver active current with GPS in acquisition mode. The Modem enters into GPS acquisition mode for approximately 30 seconds after exiting from sleep mode, on powerup, or when the Modem needs to re-acquire a GPS fix (approximately once every 4 hours) while the Modem is continuously powered on and not in sleep mode.

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An example power profile for a Modem powered with 3.3V can be found below in Figure 5.
Figure 5: Example current use for a Modem with a 3.3 V input from wake-up, GPS acquisition, Transmit, Receive mode, and then sleep mode. Note the two breaks in the y-axis scale.

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Transmissions from the Modem consist of short periods of high current draw conforming to the following characteristics:

Parameter

Value

Note

Transmission Length

3.7 s

Length of transmission for sending a 192 byte packet to space. Actual length may be shorter with a smaller packet size

Transmission Energy

3.4 mW-hrs (12.24 J)

Total amount of energy required for 1 transmission to space (192 bytes), when using 3.3V

Recovery

0.4s

Time

When sending multiple messages, this is the minimum amount of time that will pass before the Modem will attempt another transmission

Table 9: Sample Modem transmission characteristics for sending a user payload of 192 bytes. Modem provided with 3.3V input.

Other electrical characteristics of the Modem can be found below:

Parameter
Maximum power at antenna connector Sum total of all capacitance Sum total of all inductance Largest capacitor Largest inductor Total Input Capacitance
Table 10: Other electrical characteristics for the Modem

Value 1.122 W 257 F 16923 nH 47 F 15000 nH 57 F

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4.4 Power On/Off Control

The Modem can be powered down with the use of the $PO*1F command. Once powered down, it can be externally switched on/off by a user-supplied load switch on the VDD power rail. After power to the Modem has been removed, power should not be restored until at least 1 second has elapsed. If a Modem does not respond to software commands, remove power from the module, wait for at least 1 second, and then power it back on. If the 1 second minimum wait time is not adhered to, the reset circuit may not operate and the Modem could be placed in a non-operational state. The state is not permanent and can be rectified by the above procedure.
4.5 Serial Data Interface

The serial data interface is a CMOS serial UART 3-wire (serial Rx, serial Tx, and ground) interface at 3.3V digital signal levels over which the Modem transfers commands, responses, and message data. The serial communication parameters can be found below.

Parameter

Value

Baud Rate

115200

Data Bits

8 Bits

Parity

None

Stop bits

1 Bit

Flow Control

None

Table 11: Serial communication parameters.

In addition, the electrical characteristics for SERIAL_RX, SERIAL_TX, and GPIO1 can be found below.

Symbol Parameter

Min

Typ. Max

Unit

VIL

I/O input low level voltage

-0.3

–

0.3*3.3V V

VIH

I/O input high level voltage

0.7*3.3V –

3.3V

RPU/RPD Weak pull up/down equivalent resistor 25

40 55

(for GPIO1)

Table 12: Electrical characteristics for SERIAL_RX, SERIAL_TX, and GPIO1.

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All customer messages, data, and settings are stored in non-volatile memory. As such, after a power cycle, customer settings as well as any messages that have not yet been transmitted over the Swarm network will be retained on the Modem. The read/write lifetime of the Modem memory exceeds 20 years.
4.6 LED Indicators

The Modem contains three indicator LEDs, whose function is described below. All LEDs are off when the Modem is placed into sleep mode.

LED Function

Green During the bootup sequence the green LED will be on solid for 3 seconds.

During normal operation after bootup and before shutdown, the green LED will blink 100ms every 5 seconds while the Modem is powered on. This is a “heartbeat” indication that the Modem is working as expected.
Red After power is applied until the Modem begins booting, the red LED will be on solid for 10 seconds.

After bootup and while the Modem is acquiring a GPS fix, the red LED will flash quickly until a valid GPS fix has been found. Then the red LED will shut off during normal operation.

After waking up from sleep, and before a fresh GPS fix has been acquired, there will be a single red LED flash every 5 seconds (following the green LED flash) until a fresh GPS fix has been found. Then the red LED will again shut off during normal operation.

During the shutdown sequence, the red LED will be on solid until 3.3V power is removed from the board.

Blue

The blue LED will be on solid when the Modem is actively receiving from a Swarm satellite

Table 13: LED functions.

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5 Design Guidance

This section describes the recommended design practices for successful integration of the Modem.
5.1 Input Connections

The Swarm Modem utilizes standard 51 mm x 30 mm mPCIe form factors that require an industry standard connector listed below. All voltage pins need to be connected in such a way to minimize ground loops, often down by using a via to a power/ground plane. A method of retaining the Modem is also required, whether it be a retaining clip or screws.
Below are example connectors, retaining clips, and their part numbers. Many vendors and styles exist from vendors such as DigiKey/Mouser/Newark.

Example Connectors JAE: MM60-52B1-B1-R850 TE Connectivity: 2041119-2

Example Retaining Clips JAE: MM60-EZH039-B5-R850 TE Connectivity: 1717832-2

Altium footprints with correct connector/retaining clip spacing can be found on our Documentation page which use the JAE example parts shared above.
5.2 Decoupling and Feed-through Capacitors
We require a minimum amount of decoupling capacitance in order to reduce/eliminate any high frequencies from the input supply reaching the Modem input terminals.
Choose Ceramic capacitors rated for 16V or greater, X5R or better

Qty

Size

100 nF

10 F

100 F

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In addition to the decoupling capacitors above, we also highly recommend a feed-through capacitor prior to decoupling to further clean up the supply voltage.

Example Feed-Through Capacitor
TDK: YFF31HC2A105MT000N
5.3 Input Voltage Examples
The Modem can be supplied via linear or switching regulator depending on the user’s requirements. The Modem has an on-board boost regulator with an input voltage range of 3.0V to 5.0V. Most customers are operating remotely and use switching regulators for high efficiency and battery applications. We have provided example parts below. The customer can use these as a baseline for starting their own designs using other suppliers.

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It’s recommended that users pick a regulator capable of 2A for the modem alone; all other user peripherals should be in addition to the 2A regulator.

Example Regulator Analog Devices: LTC3113
ST: LD39200

Description
3A Low Noise Buck-Boost DC/DC Converter
2A High PSRR Ultra low drop linear regulator with reverse current protection

Proper layout and design of switching regulators are critical to reduce conducted and radiated emission on-board. These are often coupled onto the power and antenna of the Modem increasing RSSI and impeding successful transmission. We highly recommend an RF CAN over any switching regulator to eliminate the risk of radiated emissions from the switcher. An example RF CAN and proper layout is pictured below.

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5.4 Communications
A Serial Debug Header is included in the sample hardware design to upgrade the Modem firmware. It is critical that users include this, or similar, header in their design to provide serial access to the Modem, which can be used to upgrade to future firmware versions and for debugging. The Serial Debug Header requires the following connections: SERIAL_RX, SERIAL_TX, and GND. It is highly recommended that the designer use a 6-pin connector to easily accommodate a COTS TTL (USB-A to UART) cable or Tag-Connect, for example:
Figure 6: Example of a Serial Debug Header, shown on the Swarm Eval Board

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5.4.1 Level Shifting
The Modem is 3.3V logic capable, so interfacing with higher or lower level logic systems will require level shifting. There are many methods to level shift a signal ranging from simple mosfets and resistors to dedicated IC’s to handle the operation. Level shifting should be bi-directional.

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5.5 Example Power Regulation Design

Figure 7: Schematic of a buck-boost-solar charger design for a Swarm Modem integration. Full schematic for the Swarm Eval kit available at https://swarm.space/developertools/

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Figure 8: Sample hardware reference design integration for the Swarm Modem. This is a low noise buck-boost-solar charger example with the Swarm Modem (reference design files can be found at www.swarm.space/developertools/ ). A 6-pin serial programming header (upper-left of image) is highly encouraged so that the Modem firmware can be easily updated in the future. Qty 3 18650 lithium rechargeable batteries in parallel are used in this reference design. The circuit fits into BUD Industries IP68 waterproof case Model # PU-16533-C, with the use of 4 standoffs.

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6 RF Interfaces
This section describes the physical characteristics of the RF connectors and specifications of the RF Interface.
6.1 RF Connectors
The Modem’s satellite and GPS connectors are male U.FL connectors [TE Connectivity Part Number 1909763-1]. This is a surface mount connector that is directly attached to the Modem. A Swarm VHF antenna must be used to ensure that the antenna is tuned appropriately to make successful transmission to the Swarm satellites. Swarm antennas are tuned for VSWR (between Swarm Bands) with a max < 0.5.
6.2 RF Antenna
For illustrative purposes, a picture of the Swarm ¼-wave antenna is shown in Figure 9.

Figure 9: Swarm Coiled ¼ Wave Antenna.

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6.2.1 Antenna Characteristics
The Modem is certified with the following antenna as described below. No power reduction compensation is required for use with this antenna.

Swarm Coiled ¼ Wave Antenna Parameter

Value

Length

22.0 cm

Diameter (Connector)

11.2 mm

Diameter (along major length)

7.6 mm

Weight

31.5 g

Operating Temperature

-55 °C to +130 °C

Operating Humidity

0-100% humidity, condensable

Impedance

50 Ohms nominal

Polarization

Linearly Polarized

VSWR (between Swarm Bands)

Max < 0.5

Gain

2.0 dBi

Nominal Output Power

30 dBm (Declared)

Frequency

137.000-138.000 MHz (Rx) 148.000-150.000 MHz (Tx)

Connector

SMA male (U.FL to SMA female cable required)

Antenna Ground Plane Antenna Height Requirement

Required, see section 6.2.2 1m above the ground/solid surfaces

Antenna Classification

Mobile, Fixed

Minimum separation distance from body

36 cm

Table 14: Antenna characteristics for Swarm Coiled ¼ Wave Antenna.

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RF Antenna Guidance
The antenna gain shall be < 5 dB for an ideal 0 dBi radiator. If using an antenna other than the Swarm Coiled ¼ wave antenna, please refer to the notes below:
An antenna that has a gain of > 5dB will not be compliant with current certifications. The end-user will have to get a Supplier’s Declaration of Conformity (SDoC) and use
Swarm’s FCC/IC ID as included. If the antenna being used has > 2dBi of gain, then the antenna will have to be evaluated
for SAR.
GPS Antenna Guidance
A GPS antenna is required for operation. Any passive GPS antenna with an appropriate connection to the Modem’s U.FL male connector is acceptable for use. One such example of a passive antenna is: [Molex Part Number 1461860300].
Active GPS antennas are supported at 3.3V and up to 35mA. Any active antennas that require a different voltage or maximum current must be powered by the user’s host device.

Example u.fl to SMA cable Taoglas: CAB.721

Example u.fl to u.fl cable Wurth: 636201050100

6.2.2 Ground Plane Requirements
An antenna counterpoise or antenna ground plane is required for the Swarm Coiled ¼ Wave Antenna. Ground planes are electrically conductive surfaces that are connected to the ground conductor of the antenna that serve as a reflecting surface for radio waves.
To date, Swarm has reliably communicated with its satellites using a coiled ¼-wave antenna with a 50 cm long, 20 AWG (0.812mm diameter) wire descending from the ground of the SMA connector of the antenna mount. Swarm has also reliably communicated with its satellites using a solar panel off to one side as the ground plane of sufficient size: 30cm x 30cm x 0.3cm
Integrated solutions are recommended to be designed with the use of a symmetrical ground plane or similar RF grounding solution for the best results with a Swarm-provided antenna.

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Figure 10: Example ¼-wave antenna with a (Swarm) 9W solar panel serving as the required 30 x 30 cm ground plane off to one side. Tested extensively in the field and works well.

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6.3 Antenna Debugging
To quickly verify the antenna connection to Modem: 1. Power on the Modem. 2. After bootup, issue $RT 1*17. The noise floor the Modem hears (in dBm) will begin displaying at a rate of once per second. 3. While the Modem’s LED is blinking red rapidly (indicates it has not yet acquired a GPS fix) a. Touch the Modem’s antenna with your hand or with another object. The noise floor measurement should noticeably change. b. The Modem will not transmit until it has a GPS fix and it hears a Swarm Satellite. There is no risk of the Modem transmitting during this procedure if the red LED is blinking rapidly.

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7 Software interface
Message types
There are two types of messages:
Unsolicited messages – which include status messages, date/time and GPS information, and notifications that user data has been received. By default most of these are set to not appear, and user settings of these messages persist through restarts and power cycles.
Command responses – which include responses to input commands, as well as notifications that user data has been sent or settings have been updated
General command structure
All messages sent and received are NMEA formatted sentences. NMEA sentences are terminated with a single newline character. Each sentence begins with a $ and ends with xx where xx is a two digit hexadecimal checksum of the characters between the $ and xx. The checksum conforms to the NMEA standard and does not include either the $ or the xx. Messages with a bad checksum will fail to be parsed and produce the following response.
$CMD? ERR,CMD_NMEACHECKSUMFAIL21
A sample implementation of the NMEA checksum can be found below (written in C)
A $ will never occur within a command, and may be used to reset the receiving state machine.
An may occur within a command. The receiving state machine will verify the last three characters in the command are xx after the n is received and before the checksum is calculated. Each x may be any legal ASCII character in the range 0..9, A..F, or a..f.
An example command is provided below to illustrate the command structure and a valid checksum. This command returns the most recent date/time message :
$DT @70
$DT 20190408195123,V41

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Command timing
Once the $ is received, all subsequent characters must occur within 250 milliseconds of the previous character. If the inter-character delay exceeds 250 ms, the command will be silently discarded, and the receiving state machine will consume and ignore any characters received until the next $.
Command responses
An OK response confirms that the input parameters have been updated in response to a command. An ERR response indicates that the command could not be parsed successfully, and an error type details the problem. Note that additional or invalid characters included between the two-character command designator and the of the command can cause an error response. ERR responses have the following syntax:
$ ERR,xx

Value cmd error_type

Description The two-character command designation Type of error encountered during command processing

The follow error type messages will be provided:

Value CMD_BADPARAM CMD_BADPARAMLENGTH CMD_BADPARAMVALUE CMD_INVALIDCHAR CMD_NOTIMPLEMENTED CMD_PARAMMISSING CMD_PARAMDUPLICATE

Description Unrecognizable parameter after command A parameter has an incorrect length A parameter has a value that is out of range A parameter has an invalid character The command is not recognized as valid A required parameter is missing A parameter has been duplicated

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Boot-up sequence
The user application should ignore any characters received during startup until the following NMEA sentence has been received:
$M138 BOOT,RUNNING2a
The bootloader may output non-NMEA formatted messages during this time. These messages include, but are not limited to: status messages, firmware update progress messages, and error messages. These messages should be ignored and are for Swarm debugging purposes only.
GPS Date/Time Reference
The Modem will enter its GPS acquisition state once the boot-up sequence is complete. Please refer to Figure 11 for estimates of how long the Modem will take to acquire a valid date/time reference. The user application should not send any transmit data ($TD) commands until the following NMEA sentence has been received:
$M138 DATETIME56

Figure 11: Time Estimates for GPS Date/Time Reference Update

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Note that ALL time representations now use the T date and time delimiter as indicated in ISO 8901 EXCEPT FOR THE $DT COMMAND. Ex. 2022-01-26T08:30:00.
Messages
All messages sent to or from the Hive have an Application ID tag associated with them. The Application ID can be an arbitrary number from 0 to 64999, and may be used by the user to organize messages (ex: Application ID 1000 could be used for device telemetry, 2000 for commands to the device and 3000 for emergencies). Swarm reserves Application ID values 65000 to 65535 for internal use. Specifying an Application ID in the reserved range will result in unexpected operation and the messages may be lost.
See the $TD – Transmit Data command section in the command directory below for an example implementation of the Application ID.
Implementation of NMEA checksum in C
uint8_t nmeaChecksum (const char *sz, size_t len) {
size_t i = 0; uint8_t cs;
if (sz [0] == ‘$’) i++;
for (cs = 0; (i < len) && sz [i]; i++) cs ^= ((uint8_t) sz [i]);
return cs; }

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Table of Commands and Messages

Name

Description

$CS

Configuration Settings

$DT

Date/Time Status

$FV

Firmware Version Read

$GJ

GPS Jamming/Spoofing Indication

$GN

Geospatial Information

$GP

GPIO1 Control/Status

$GS

GPS Fix Quality

$MM

Messages Received Management (2-way operation)

$MT

Messages to Transmit Management

$PO

Power Off

$PW

Power Status

$RD

Receive Data Unsolicited Message

$RS

Restart Device

$RT

Receive Test

$SL

Sleep Mode

$M138

Modem Status Unsolicited Message

$TD

Transmit Data

Table 15: Table of all Modem commands

Unsolicited Messages Yes Yes Yes Yes
Yes Yes Yes Yes Yes

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$CS – Configuration Settings

Retrieve and display the configuration settings for the Swarm device ID. These settings are determined by Swarm for identifying and communicating with each individual device. Since there are no variable parameters, the correct checksum has been provided below.
$CS10
Returns:
$CS DI=,DN=xx

Value dev_ID dev_name

Description Device ID that identifies this device on the Swarm network Device type name

Notes: See the section Command responses for a description of . Example: $CS10 $CS DI=0x00e57,DN=M13843 The Device ID is 0x00e57, and the device is a M138 Modem

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$DT – Date/Time Status
Set or query the rate for $DT unsolicited report messages for date and time. Also can retrieve the most current $DT message. See unsolicited message description for $DT message format.
$DT <@|?|>*xx

Parameter @ ? rate

Description Repeat most recent $DT message Query current $DT rate Disable or set rate of $DT messages

Returns one of:

Value $DT

,xx $DT xx $DT OKxx $DT ERR,xx

Description The most recent $DT message. The current $DT rate rate updated successfully Command input error

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Parameter YYYY MM DD hh mm ss flag

Description Year (1970..2099) Month (01..12) Day (01..31) Hour (00..23) Minutes (00..59) Seconds (00..59) I Date/time is invalid V Date/time is valid

Notes:
See the section Command responses for a description of .

is a value between 1 and 2147483647 (231-1) or 0. It will be the number of seconds in between each message. If is 0, no messages will be sent. If is valid, no $DT messages will be sent by the device until the GPS has obtained a valid time reference to set its internal date and time, as indicated by the $M138 DATETIME*56 message. The valid flag will show V if the modem has acquired a valid time reference at least once since powering on.

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Examples: Calling the most recent date/time message: $DT @70 $DT 20190408195123,V41 Returns a date/time of April 8th, 2019 7:51:23 PM GMT. The date/time is valid. does not have to be valid to call the most recent date/time message.
Setting the rate of date/time messages: $DT 30003 $DT OK34 Sets the rate of date/time messages to one message every 300 seconds.
Querying the rate of date/time messages: $DT ?0f $DT 6036 Returns a rate of one message every 60 seconds.

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$FV – Firmware Version Read
Returns the current device firmware version. Since there are no parameters, the correct checksum has been added.
$FV*10
Returns one of:

Value $FV xx $FV ERR,xx

Description The current firmware version Command input error

Notes: See the section Command responses for a description of . Example: $FV10 $FV 2021-07-16T00:10:21,v1.1.074

The firmware version on the device is 1.1.0

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$GJ – GPS Jamming/Spoofing Indication
Set or query the rate for $GJ unsolicited report messages for jamming and spoofing indicators. Also can retrieve the most current $GJ message.

$GJ <@|?|>*xx Parameter Description

@ ? rate

Repeat most recent $GJ message Query current $GJ rate Disable or set rate of $GJ messages

Returns one of:

Parameter

Description

$GJ ,*xx The most recent $GJ message.

$GJ *xx

The current $GJ rate

$GJ OKxx $GJ ERR,xx

Parameters updated successfully Command input error

Parameter spoof_state
jamming_level

Description
0 Spoofing unknown or detection deactivated 1 No spoofing indicated 2 Spoofing indicated 3 Multiple spoofing indications
Relative value ranging from 0 to 255 indicating how much carrier wave (CW) jamming is detected. 0 = no CW jamming, 255 = strong CW jamming

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Notes: See the section Command responses for a description of .

is a value between 1 and 2147483647 (231-1). It will be the number of seconds in between each message. If is 0, no messages will be sent. Examples: Calling the most recent GPS jamming/spoofing message: $GJ @*6d $GJ 1,23*31 Returns a spoof state of No spoofing indicated. The carrier wave jamming level is 23. Setting the rate of GPS jamming/spoofing messages: $GJ 3600*28 $GJ OK*29 Sets the rate of GPS jamming/spoofing messages to one message every 3600 seconds. Querying the rate of GPS jamming/spoofing messages: $GJ ?*12 $GJ 10*2c Returns a rate of one message every 10 seconds.

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$GN – Geospatial Information
Set or query the rate for $GN unsolicited report messages for geospatial information. Also can retrieve the most current $GN message.
$GN <@|?|>*xx

Parameter @ ? rate

Description Repeat most recent $GN message Query current $GN rate Disable or set rate of $GN messages

Returns one of:

Value
$GN ,,, ,xx
$GN xx
$GN OKxx
$GN ERRxx

Description The most recent $GN message
The current $GN rate Parameters updated successfully Command input error

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Parameter latitude
longitude
altitude course speed

Description
Latitude in d.dddd format (float). The latitude is presented in the N basis (negative latitudes are in the southern hemisphere)
Longitude in d.dddd format (float). The longitude is presented in the E basis (negative longitudes are in the western hemisphere)
Altitude in meters (integer)
Course in degrees (0..359) (integer). Course proceeds clockwise, with 0=north, 90=east, 180=south, and 270=west
Speed in kilometers per hour (0..999) (integer)

Notes:
See the section Command responses for a description of .

is a value between 1 and 2147483647 (231-1). It will be the number of seconds in between each message. If is 0, no messages will be sent. If is valid, no $GN messages will be sent by the device until the GPS has obtained a valid position reference as indicated by the $M138 POSITION*4e message .

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Examples: Calling the most recent GPS message: $GN @69 $GN 37.8921,-122.0155,77,89,201 Returns a location of 37.8921N, 122.0155W. The device’s altitude is 77m, its course is 89 degrees, and it is moving at 2 kilometers per hour.
Setting the rate of GPS messages: $GN 302a $GN OK2d Sets the rate of GPS messages to one message every 30 seconds.
Querying the rate of GPS messages: $GN ?16 $GN 152d Returns a rate of one message every 15 seconds.

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$GP – GPIO1 Control/Status
This command allows control of the GPIO1 pin to allow indications or control the operation of the Modem.
$GP <@|?|>*xx

Parameter @ ? mode

Description Read pin state (digital input and ADC modes ONLY) Display current GPIO1 mode Set GPIO1 pin mode

Returns one of:
Value $GP Vxx $GP <H|L>xx $GP xx $GP OKxx $GP ERR,*xx

Description GPIO1 ADC reading in volts (mode 1) GPIO1 digital input status (mode 2) The current $GP mode Parameters updated successfully Command input error

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Notes: See the section Command responses for a description of .
The ? option allows reading back the current setting. The mode parameter allows specifying how the GPIO1 pin will operate. The available modes are:

Mode 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Description Analog, pin is internally disconnected and not used (default) Analog ADC, pin can be read to measure input voltage (0-3.3V) Input, pin can be read as a general purpose digital input (High or Low) Input, low-to-high transition exits sleep mode Input, high-to-low transition exits sleep mode Output, set low as a general purpose digital output Output, set high as a general purpose digital output Output, low indicates unread messages pending for user Output, high indicates unread messages pending for user Output, low indicates unsent messages pending for transmit Output, high indicates unsent messages pending for transmit Output, low indicates unread or unsent messages Output, high indicates unread or unsent messages Output, low indicates sleep mode is active. Otherwise output is high Output, high indicates sleep mode is active. Otherwise output is low

Note
1 1 2 2 3 3 4 4

It is the responsibility of the user to provide pull-up resistors to the 3.3V supply rail. See the reference design for resistor sizing. All output modes are open drain.
(1) – If either of these modes are selected, the pin will indicate if the Modem has received one or more unread messages and is holding them for the user. If multiple messages are pending for the user, the pin will maintain the state until all messages have been read.

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(2) – If either of these modes are selected, the pin will indicate if the Modem is holding one or more unsent messages until they can be transmitted. If multiple messages are pending for the user, the pin will maintain the state until all messages have been sent.
(3) – If either of these modes are selected, the pin will indicate if the Modem is holding at least one unread incoming message or at least one unsent outgoing message.
(4) – If either of these modes are selected, the pin will be set to the selected state after the user has issued the $SL command. The pin will return to the awake state only if the sleep mode is terminated by the wakeup time parameter being reached, or alternatively if activity is detected on the serial RX line.

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Examples: Querying the GPIO1 pin mode: $GP ?08 $GP 700 The GPIO1 pin mode is set to Output, low while in sleep mode. Otherwise output is high.
Reading the GPIO1 pin in ADC mode (must be in mode 1): $GP @77 $GP 3.282V44 The GPIO1 pin mode has an ADC reading of 3.282V.
Reading the GPIO1 pin in digital input mode: $GP @77 $GP L7b The GPIO1 pin mode is a logic low.
Setting the GPIO1 pin mode to input and wake on a high-to-low transition: $GP 403 $GP OK33 Sets the GPIO1 pin mode to input and wake on a high-to-low transition.

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$GS – GPS Fix Quality
Set or query the rate for $GS unsolicited report messages for GPS fix quality. Also can retrieve the most current $GS message..
$GS <@|?|>*xx

Parameter @ ? rate

Description Repeat most recent $GS message Query current $GS rate Disable or set rate of $GS messages

Returns one of:

Parameter
$GS ,,,, xx
$GS xx
$GS OKxx
$GS ERR,xx

Description The most recent $GS message
The current $GS rate Parameters updated successfully Command input error

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Parameter hdop vdop gnss_sats unused fix_type

Description Horizontal dilution of precision (0..9999) (integer = actual hdop

1. Vertical dilution of precision (0..9999) (integer = actual vdop * 100) Number of GNSS satellites used in solution (integer) Always reads as 0, unused NF No fix DR Dead reckoning only solution G2 Standalone 2D solution G3 Standalone 3D solution D2 Differential 2D solution D3 Differential 3D solution RK Combined GNSS + dead reckoning solution TT Time only solution

Notes:
See the section Command responses for a description of .

is a value between 1 and 2147483647 (231-1). It will be the number of seconds in between each message. If is 0, no messages will be sent. If is valid, no $GS messages will be sent by the device until the GPS has obtained a valid position reference as indicated by the $M138 POSITION*4e message.

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Examples: Setting the rate for geospatial information messages to 1 per second: $GS 105 $GS OK30 If is valid, no $GN messages will be sent by the device until the GPS has obtained a valid position reference as indicated by the $M138 POSITION4e message.
Calling the most recent geospatial information message: $GS @74 $GS 109,214,9,0,G346 Returns an HDOP of 1.09, VDOP of 2.14, the device is using 9 GNSS satellites for this solution, and it is a Standalone 3D solution.
Querying the rate of geospatial information messages: $GS ?0b $GS 120*07 Returns a rate of one message every 120 seconds.

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$MM – Messages Received Management (2-way operation)
Manage received messages in the device incoming message queue. Has ability to return the count, mark, and delete messages.
$MM <C=<U|>|D=<msgID|R|>|L=<msgID|U>|M=<msgID|>|N=<D|E|?>|R=<msgID|O|N>>xx

Parameter C=<U|> D=<msgID|R|> L=<msgID|U>
M=<msgID|*> N=<D|E|?> R=<msgID|O|N>

Description
Return count of unread (U) or all () messages Delete message ID (msgID), all read (R), or all messages () List message ID (msgID), or the 10 oldest received unread messages (U). Listing a message by msgID will mark it as read (R) Mark message ID (msgID) or all messages (*) as read Message notifications disabled (D), enabled (E), or query (?) Read message ID (msgID), oldest (O), or newest (N) message

Returns one of:
Parameter $MM xx $MM ,,,xx $MM MARKED,xx $MM DELETED,xx $MM OKxx $MM ERR,xx $MM ERR,DBX_INVMSGIDxx $MM ERR,DBX_NOMORExx

Description Number of messages read/all/deleted Response to reading, or listing, a message

marked as read successfully deleted successfully Message command succeeded Command input error Invalid message ID in D, L or R command No messages found when using R=

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Notes:
See the section Command responses for a description of .
Messages have three states: Unread, read, and deleted. Once an unread message is read, its state changes to read. It can subsequently be read again when called by its msgID. If a message is deleted, it can no longer be counted, read, marked, or deleted.
If a message is marked read using the M= or M=* command, marking it as read again is not an error.

is a number indicating the number of messages that are unread in response to the C=U command, total number of read and unread messages in response to the C=* command, or the number of messages deleted in response to the D=* command. is the application ID tag of the message. is in the same format as the original $RD response returns. is assigned by the device, and is an unsigned 64-bit value comprised of the device ID, a day of year counter, and a message of day counter. Responses that have a 0 as the message ID indicate the message has not been placed in the queue and therefore has no ID. The value should be treated as a simple arbitrary number. is the epoch seconds time when the message was received by the Modem.

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Examples: Counting all unread messages: $MM C=U0b $MM 313 Three messages are unread.
Listing a specific received message: $MM L=442882647668965 $MM AI=0,68692066726f6d20737761726d,4428826476689,160563959865 The received message (msg_id = 4428826476689) is returned. The hexadecimal data returned is 68692066726f6d20737761726d (in ascii = “hi from swarm”). The epoch seconds at which the Modem received the message is 1605639598 (Date/Time = Tuesday, November 17, 2020 6:59:58 PM). Message with msg_id 4428826476689 has been marked as read. Listing the oldest received unread messages: $MM L=U04 $MM AI=0,68692066726f6d20737761726d,4428826476689,160563959865 $MM AI=0,686f6c6120646573646520737761726d,4428826476690,160563966463
Two received messages are listed with a line each. None of the messages are marked as read. This command will list up to 10 of the oldest unread received messages.
Deleting all read messages: $MM D=R0b $MM 4*14 Four read messages were deleted.

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Marking a specific message as read: $MM M=2199023511142656 $MM MARKED,219902351114261e Message with msg_id 21990235111426 has been marked as read.
Reading the newest received message: $MM R=N01 $MM AI=10650,6578616d706c65206d657373616765,21990235111426,158449427552 The message (msg_id = 21990235111426) is returned. The message was sent with the application ID 10650. The hexadecimal data returned is 6578616d706c65206d657373616765 (in ascii = “example message”). The epoch seconds at which the Modem received the message is 1584494275 (Date/Time = Wednesday, March 18, 2020 1:17:55 PM). This message is now marked as read. Reading the newest received message again: $MM R=N01 $MM ERR,DBX_NOMORE5c There are no existing unread messages.
Enable message notifications: $MM N=E16 $MM OK24 Message notifications are now enabled.

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Query message notifications:
$MM N=?6c $MM N=E16 Message notifications are enabled.

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$MT – Messages to Transmit Management

Manage messages to be transmitted in the device outgoing message queue. Has ability to return the count, list, and delete unsent messages.
$MT <C=|D=<msgID|U>|<L=msgID|U>>*xx

Parameter C= D=<msgID|U> L=<msgID|U>

Description
Return count of unsent (U) messages Delete message ID (msgID) or all unsent (U) messages List message ID (msgID) messages, or the 10 oldest unsent (U) messages

Returns one of: Parameter $MT

Description Number of unsent messages

$MT ,,,*xx Response to listing a message

$MT DELETED,*xx

deleted successfully

$MT OK*xx

Message command succeeded

$MT ERR,*xx

Command input error

$MT ERR,DBX_INVMSGID*xx

Invalid message ID in D or L command

$MT ERR,DBX_NOMORE*xx Notes:

No messages found

See the section Command responses for a description of .

is a number indicating the number of messages that are unsent in response to the C=U command or the number of messages deleted in response to the D=U command

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is in the same format as the original $TD command accepts for message content is assigned by the device, and is an unsigned 64-bit value comprised of the device ID, a day of year counter, and a message of day counter. Responses that have a 0 as the message ID indicate that the message has not been placed in the queue and therefore has no ID. The value should be treated as a simple arbitrary number.

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Examples: Counting all unsent messages: $MT C=U12 $MT 123a Twelve messages are unsent.
Listing a specific unsent message: $MT L=44288264766897c $MT AI=0,68692066726f6d20737761726d,4428826476689,16056395987c The unsent message (msg_id = 4428826476689) is returned. The hexadecimal data returned is 68692066726f6d20737761726d (in ascii = “hi from swarm”). The epoch seconds at which the Modem received the message is 1605639598 (Date/Time = Tuesday, November 17, 2020 6:59:58 PM).
Listing the oldest unsent messages: $MT L=U1d $MT AI=0,68692066726f6d20737761726d,4428826476689,16056395987c $MT AI=0,686f6c6120646573646520737761726d,4428826476690,16056396647a Two messages are unsent and are listed with a line each. This command will list up to 10 of the oldest unsent messages.
Deleting all unsent messages: $MT D=U15 $MT 1*08 One message was deleted.

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$PO – Power Off
Power off the device. If fully supported, after issuing $PO1f the customer should command any Modem power supplies to disconnect. If power is not disconnected, the Modem enters a low power mode until power is completely removed and restored. Since there are no variable parameters, the correct checksum has been added.
$PO1f
Returns one of:

Value $PO OKxx
$PO ERR,xx

Description
Command has been accepted and the Modem will immediately attempt to power off
Command input error

Notes:
The $PO1f command should be given anytime power is removed from the modem. See the section Command responses for a description of .
An OK response confirms that the Modem will shut down. The user should disconnect power from the Modem at this point. If left connected, the Modem will draw approximately 3mA on its 3.3V input. The Modem will not boot again until power has been completely removed and then restored.
Example:
$PO1f
$PO OK3b
$M138 BOOT,SHUTDOWN65

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$PW – Power Status
Set or query the rate for $PW unsolicited report messages for device power state. Also can retrieve the most current $PW message.
$PW <@|?|>*xx

Parameter @ ? rate

Description Repeat most recent $PW message Query current $PW rate Disable or set rate of $PW messages

Returns one of:
Parameter $PW ,,,, xx $PW xx $PW OKxx
$PW ERR,xx

Description The most recent $PW message
The current $PW rate Parameters updated successfully Command input error

Parameter cpu_volts unused temp

Description Voltage measured at input to the CPU Will always show as 0.00000 CPU Temperature in degrees C to one decimal point (float)

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Notes: See the section Command responses for a description of .

is a value between 1 and 2147483647 (231-1). It will be the number of seconds in between each message. If is 0, no messages will be sent. Examples: Calling the most recent power status message: $PW @*67 $PW 3.28700,0.00000,0.00000,0.00000,28.0*3d Returns a CPU voltage of 3.287V and device temperature of 28.0. Setting the rate of power status messages: $PW 30*24 $PW OK*23 Sets the rate of power status messages to one message every 30 seconds. Querying the rate of power status messages: $PW ?*18 $PW 900*1e Returns a rate of one message every 900 seconds.

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$RD – Receive Data Unsolicited Message
This unsolicited message provides an ASCII-encoded hexadecimal string with the user data received from the Swarm network. Some fields also include signal quality information for the received message. Received data unsolicited messages can be enabled/disabled using the $MM command with the message notification option.
$RD ,,,,*xx

Parameters appID rssi snr fdev data

Description Application ID tag of message Received signal strength in dBm for packet (integer) Signal to noise ratio in dB for packet (integer) Frequency deviation in Hz for packet (integer) ASCII encoded data packet

Example:
$RD AI=6078,RSSI=-84,SNR=12,FDEV=9,596f7527766520676f74206d61696c21*6e
The received packet has an application ID of 6078, a rssi of -84 dBm, a snr of -12 dB, and a fdev of 9 Hz. The returned encoded hexadecimal data from the packet is 596f7527766520676f74206d61696c21 (in ascii = “You’ve got mail!”).

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$RS – Restart Device
Perform a software cold restart of the device. This command has an optional parameter that can also be used to erase the incoming and outgoing message storage before performing the restart.
$RS [deletedb]*xx

Parameter deletedb

Description Delete incoming and outgoing message storage prior to restart

Returns one of: Value $RS OKxx
$RS ERR,xx

Description
Command has been accepted and the device will immediately perform a hardware restart
Command input error

Notes: See the section Command responses for a description of . An OK response confirms that the device will successfully restart. No external power cycling is required. Example: $RS01 $RS OK25 $M138 BOOT,RESTART*3a

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$RT – Receive Test
Set or query the rate for $RT unsolicited report messages for device power state. Also can retrieve the most current $RT message.
$RT <@|?|>*xx

Parameter @ ? rate

Description Repeat most recent $RT message Query current $RT rate Disable or set rate of $RT messages

Returns one of:

Parameter

Description

$RT RSSI=,SNR=,FDEV =,TS=,DI=xx $RT RSSI=xx
$RT xx $RT OKxx $RT ERR,*xx

The most recent $RT message from a satellite. Appears independently of the rssi_background noise messages
The most recent $RT message. This is a measure of the background noise environment (and is not related to rssi_sat)
The current $RT rate
Parameters updated successfully
Command input error

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Parameter rssi_bkgnd
rssi_sat snr fdev time sat_id

Description

Received background noise signal strength in dBm for open channel (integer).

For reliable operation, this value should consistently be less than (more negative) than -93 dBm:

rssi_bkgnd >= -90 dBm rssi_bkgnd <= -93 dBm rssi_bkgnd = -97 dBm rssi_bkgnd <= -100 dBm rssi_bkgnd <= -105 dBm

Bad (not likely to work) Marginal OK Good Great

Received signal strength in dBm for packet from satellite (integer)

Signal to noise ratio in dB for packet (integer)

Frequency deviation in Hz for packet (integer)

Date and time (UTC) of received packet

Device ID of satellite heard (hexadecimal)

Notes:
See the section Command responses for a description of .

is a value between 1 and 2147483647 (231-1). It will be the number of seconds in between each message. If is 0, no messages will be sent, and no packets received from a satellite will be displayed. For reliable performance, the noise floor can be measured with an antenna connected to the device in the final built-up configuration. The rssi_bkgnd value reported by $RT should be less than (a more negative number) than -93 dBm. If the rssi_bkgnd noise floor is more than -93 dBm (a less negative number, e.g. -88 dBm), then the customer should relocate the device to a different location, reconfigure the device ground plane, and also check that their DC-DC power supplies on their own PCB are not injecting RF background noise into the device.

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Examples: Calling the most recent receive test message. This will return the last packet received from a satellite: $RT @66 $RT RSSI=-102,SNR=-1,FDEV=426,TS=2020-10-02T13:56:21,DI=0x00056870
Returns a satellite packet rssi_sat of -102 dBm, SNR of -1 dB, frequency deviation of 426 hz, a received time of October 2nd, 2020 at 1:56:21 PM, and the satellite’s device ID is 0x000568.
Setting the rate of receive test messages: $RT 117 $RT OK22 Sets the rate of receive test messages to one message every 1 second. The format of these scheduled messages will be the simple noise floor message. Any packets received from a satellite will be displayed as they are received, independently of the $RT rate.
Querying the rate of receive test messages: $RT ?19 $RT 513 Returns a rate of one message every 5 seconds.

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$SL – Sleep mode
This command puts the device into a low-power sleep mode. $SL [S=|U =<[YYYY-MM-DD ]T[hh:mm:ss]>]*xx

Parameter S= U=<[YYYY-MM-DD ]T[hh:mm:ss]>

Description Sleep for this many seconds Sleep until date (optional) and time

Returns one of: Value $SL OKxx
$SL WAKE,xx $SL ERR,GPS_TIMENOTSETxx $SL ERR,xx

Description
Sleep period accepted, device is now non-responsive Device has woken from selected sleep mode Time not yet set from GPS Command input error

The S parameter is the number of seconds to sleep. This value may range from 5 to 31536000 (approximately 1 year) seconds. If the command is accepted, the device will emit $SL OK and enter sleep mode for the requested duration.

The U parameter is a time and optional date the device should sleep until and then wake. If the date is not specified and the time to sleep until is less than the current time, the time is presumed to be the next day. For example, if the current time is 11:00:00 and $SL U=09:00:00 is issued, the device will wake 22 hours from now. If a date and time are specified, and that date/time is before the current date/time, $SL WAKE will be immediately issued.

The $SL WAKE, message is emitted after the Modem wakes from a user- commanded sleep mode. The value of cause will be one of the following:

Cause

Description

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GPIO SERIAL TIME

GPIO input changed from inactive to active state Activity was detected on the RX pin of the Modem’s UART The S or U parameter time has been reached

If UART activity wakes the Modem, the TIMEOUT message will not be emitted as the Modem is now awake.
In sleep mode, the real-time clock is not GPS disciplined, and is therefore subject to some degree of drift. The longer the device is asleep, the more the drift will accumulate. The drift is estimated to be 20ppm, so if the Modem is commanded to sleep for 100 hours, the drift may result in the Modem actually sleeping in the range of 99.998 to 100.002 hours. The user should be aware of this when selecting a sleep with a long duration.
If the GPIO1 pin is configured as an input to wake the Modem, the sleep mode will be terminated if activity occurs on GPIO1. If the GPIO1 pin is configured as an output that indicates the Modem’s sleep mode, GPIO1 will transition to the appropriate state if the $SL OK message is emitted.
Notes:
See the section Command responses for a description of .

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Examples: Commanding the Modem to sleep for 3600 seconds (1 hour): $SL S=360054 $SL OK3b $SL WAKE,TIME @ 2019-04-11T18:58:0303 If the Modem receives any serial input before the planned wake time, then the Modem will wake with a message such as: $SL WAKE,SERIAL @ 2019-04-11T18:57:451b Similarly, if the GPIO1 pin is configured to wake on a high-to-low (or low-to- high) transition, then on transition on the GPIO1 pin, the Modem will also wake with a message such as: $SL WAKE,GPIO @ 2019-04-11T18:57:550b
Commanding the Modem to sleep until October 1st, 2021 at 4:30:00 PM: $SL U=2021-10-01T16:30:0006 $SL OK*3b

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$M138 – Modem Status Unsolicited Message
These unsolicited status messages indicate the readiness of the Modem for normal operation. This includes the conditions at power up, GPS acquisition, and certain error conditions. Modem status messages cannot be disabled.
$M138 ,[]*xx

Parameter msg

Description
BOOT – Boot process progress with the following data reason: ABORT – A firmware crash occurred that caused a restart DEVICEID – Displays the device ID of the Modem POWERON – Power has been applied RUNNING – Boot has completed and ready to accept commands UPDATED – A firmware update was performed VERSION – Current firmware version information
DATETIME – The first time GPS has acquired a valid date/time reference POSITION – The first time GPS has acquired a valid position 3D fix DEBUG – Debug message (data – debug text) ERROR – Error message (data – error text)

Notes:
A data message follows the BOOT message to indicate the reason for the startup.
The POSITION message and DATETIME message may occur in any order. Depending on the GPS signal quality, it may take several minutes before either message is emitted.
The customer application should wait until the boot process is complete and it has received the $M138 BOOT,RUNNING*2a message before executing any commands.

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$TD – Transmit data
This command transmits data to the Swarm network. $TD [AI=|HD=|ET=,]<[string|data]>*xx

Parameter AI= HD=
ET= <string|data>

Description
Application ID tag for message (optional, default = 0, maximum is 64999)
Hold duration of message in seconds (optional, default = 172800 seconds, minimum = 60 seconds)
Expiration time of message in epoch seconds (optional, if omitted, same as hold_dur)
1 to 192 bytes of data (ASCII string) 2 to 384 bytes (hexadecimal written as ascii)

Notes:
See the section Command responses for a description of .
In order to send a $TD command, you must first wait for a $M138 DATETIME56 response after power up. The Modem must wait for a valid time in order to accept a transmit command. All other commands are functional prior to receiving the $M138 DATETIME56 response.

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Returns one of:

Value $TD OK,xx $TD SENT RSSI=,SNR=,FDEV=<fd ev>,xx
$TD ERR,TD_APPIDNOTANINT*xx

Description
Message accepted for sending
This is an unsolicited response that occurs at the time when the message is sent to and acknowledged by the satellite. It includes the RF information for the satellite reply.
Application ID not recognized as integer

$TD ERR,TD_APPIDTOOLARGE*xx

Application ID greater than maximum allowed

$TD ERR,CMD_TD_HOLDDURNOTANINT*xx

Hold duration not recognized as integer

$TD ERR,CMD_TD_HOLDDURTOOLONGxx
$TD ERR,CMD_TD_HOLDDURTOOSHORTxx
$TD ERR,CMD_TD_EXPIRATIONNOTANINT*xx

Hold duration OR expiration time too far in future (maximum 13 months)
Hold duration OR expiration time less than 60 seconds in future
Expiration time not recognized as an integer (epoch seconds format)

$TD ERR,CMD_TD_DATATOOLONGxx $TD ERR,DBX_OUTGOINGFULLxx
$TD ERR,GPS_TIMENOTSETxx $TD ERR,CMD_BADPARAMLENGTHxx
$TD ERR,*1c

Message is too large to send
Outgoing message queue is full. Maximum of 1024 messages may be stored in the queue.
Command received before time set by GPS
For data field: Message has odd number or non-hex characters when sending data as hexadecimal
Command input error

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Notes:
Messages may be delivered to the Hive out of sequence. It’s suggested if ordering is vital, for customers to add their own timestamp or sequence number.
The AI, HD and ET parameters are optional but must occur before the portion of the command.

is the application ID tag for the message. If this option is not specified the message will be sent with application ID 0. HD and ET affect the time when a message has expired and is no longer considered available to transmit. If neither HD or ET option is present, the default hold time of 172800 seconds (48 hours) will be used. If both options are specified, the will be ignored. The outgoing message queue is scanned periodically and messages may be removed from the outgoing queue at any time after the expiration time has passed without notice.

Application ID Value 0 to 64999

Description
The application ID tag for the message. Swarm reserves the use of application IDs between 65000 to 65535.

is the number of seconds to hold the message if it has not been sent before expiring it from the outgoing message queue.

Hold Duration Value
60 to 34819200 (13 months)

Description
The message will be considered expired if not sent within the specified number of seconds. The maximum duration is 13 months from the current time.

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is an epoch second date after which the message will be expired if it has not been sent.

Expiration Time Value

\+ 60 secs to \+ 34819200 secs

Description
The message will be considered expired if not sent before the specified time. The epoch seconds must lie between 60 seconds in the future and 13 months in the future. If not within this range an error will indicate it is too short or too long.

<string|data> may be expressed one of two different ways. If all the data to be sent is in the ASCII character range from 0x20 (space) to 0x7e (tilde), then the data may be sent as a string. A string is specified by enclosing the data in double quotes, e.g., “Hello, world”. It is permissible for the string to contain double quotes within the string, e.g., “Today is a “new” day”. If the data to be sent includes one or more character outside the 0x20 to 0x7e range, then it must be specified as pairs of hex characters (‘0’..’9′, ‘A’..’F’, ‘a’..’f’), and must be a multiple of 2. Sending ‘Hello’ as hex would be 48656C6C6F. Illegal characters or an odd number of characters will cause a CMD_BADPARAMVALUE message to be returned.

is assigned by the device, and is an unsigned 64-bit value comprised of the device ID, a day of year counter, and a message of day counter. Responses that have a 0 as the message ID indicate the message has not been placed in the queue and therefore has no ID. The value should be treated as a simple arbitrary number.

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Typical messaging flow:
1. User queues a message to be sent with application ID 40, with a hold duration time of 7200 seconds (2 hours). The use of indexing parameters in the body of the message is recommended to aid in message identification and sequencing:
$TD AI=40,HD=7200,”{“d”:”Demo message”,”t”:”2021-02-26 14:28:56″,”seq”:”00015″}”09
2. Device acknowledges receipt of message, and message enters into device’s internal outgoing message queue. Message is given the message ID of 5354468575855. The outgoing message queue provides for a maximum storage of 1024 unsent messages. The outgoing message queue is non-volatile, and messages persist through sleep mode and power cycling:
$TD OK,53544685758552a
3. If the message has not expired due to time (it was previously set to be held until 2 hours from when it was entered), when the device hears a satellite pass overhead it attempts to send any messages in its outgoing queue. Messages are scheduled to be sent in the order they were entered into the device (e.g. first in outgoing queue, first transmitted). Each message heard by the satellite is individually acknowledged with a $TD SENT response – the acknowledged message is referred to by its message ID (5354468575855)
$TD SENT,RSSI=-99,SNR=5,FDEV=32,5354468575855*6f
4. The acknowledged message is marked in the outgoing message queue for deletion by the device. Any unsent messages will be attempted to be sent by the device at a later time.

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Examples: Sending a message from the device in ASCII: $TD “{“d”:”Demo message”,”t”:”2021-02-26 14:48:56″,”seq”:”00017″}”08 $TD OK,53544685759162c $TD SENT,RSSI=-104,SNR=-3,FDEV=345,535446857591644
Sending a message from the device in ASCII that will be held for 1 hour: $TD HD=3600,”{“d”:”Demo message”,”t”:”2021-02-26 14:51:21″,”seq”:”00018″}”17 $TD OK,53544685759172d $TD SENT,RSSI=-103,SNR=2,FDEV=-67,535446857591770
Sending a message from the device in ASCII that will expire on 2022-01-01T12:34:56: $TD ET=1641040496,”{“d”:”Demo”,”t”:”2021-02-26 15:01:22″,”seq”:”00020″}”45 $TD OK,535446857591923 $TD SENT,RSSI=-100,SNR=-3,FDEV=437,53544685759194d
Sending a message from the device in ASCII with application ID 3000: $TD AI=3000,”{“d”:”Demo”,”t”:”2021-02-26 15:33:22″,”seq”:”00021″}”52 $TD OK,535446857591923 $TD SENT,RSSI=-100,SNR=-3,FDEV=437,53544685759194d

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Sending a message from the device in HEXASCII: $TD 49206C6F766520537761726D4c $TD OK,53544685759162c $TD SENT,RSSI=-107,SNR=3,FDEV=199,5354468575916*69

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Swarm M138 Modem Product Manual 1.41 User Guide

Swarm M138 Modem Product Manual 1.41

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