Airgain NL-SWDK2 NimbeLink Development Kit Version 2 User Manual

NL-SWDK2 User Manual
Airgain, Inc
Updated: April 2023

Airgain, Inc. 2023. All Rights Reserved.
Airgain, Inc provides this documentation in support of its products for the internal use of its current and prospective customers. The publication of this document does not create any other right or license in any party to use and content in or referred to in this document and any modification or redistribution of this document is not permitted.
While efforts are made to ensure accuracy, typographical and other errors may exist in this document. Airgain, Inc reserves the right to modify or discontinue its products and to modify this and any other product documentation at any time.
All Airgain, Inc products are sold subject to its published Terms and Conditions, subject to any separate terms agreed with its customers. No warranty of any type is extended by publication of this documentation, including, but not  limited to, implied warranties or merchantability, fitness for a particular purpose and non-infringement.
Airgain, Inc. is a registered trademark, and NimbeLink is a registered trademark of Airgain, Inc. All trademarks, service marks and similar designations referenced in this document are the property of their respective owners.

Introduction

This document serves as the user manual for the NimbeLink Development Kit Version 2 platform. Throughout this document the NimbeLink Development Kit Version 2 will be referred to by its abbreviated name, SWDK2, or by its part number, NL-SWDK2.
1.1 Contact Information
Airgain’s goal is to make integrating NimbeLink modems into end-user applications as easy as possible. Please send any feedback, documentation requests, or technical support questions to Airgain’s product support team at:
product.support@nimbelink.com
For purchasing information, please visit the “Part Ordering Information” section on the development kit’s product page. Any additional sales questions or requests for quotation can be directed to Airgain’s sales team at: sales@airgain.com
1.2 Orderable Part Numbers

*This modem is compatible with all NimbeLink modems using the standard NimbeLink interface. This development kit is not compatible with NimbeLink Nano products.
1.3 Additional Resources

• NimbeLink Software Developers Guide
• NimbeLink Hardware Developers Guide
• NL-SWDK2 Product Page
• NL-SWDK2 Datasheet
• NL-SWDK2 Schematic
• NL-SWDK2 Altium Design Files

1.4 Kit Contents
The SWDK2 development kit includes the following:

• 1 x NL-SWDK2 development board
• 2 x Taoglas TG.30.8113 Antennas
• 1 x NimbeLink AT&T SIM
• 1 x 12V Power Supply
• 1 x Mini-B USB Cable

The development kit does not include a NimbeLink modem. Modems must be purchased separately.

Getting Started

The following section will guide users through the getting started process with a SWDK2 development kit in a Windows 10 environment.
2.1 Data Plans
NimbeLink cellular modems do not ship with active cellular data plans, unless they are part of Airgain’s NimbeLink Bundled Data plan Service.
Devices using Airgain’s Bundled Data Plan Service ship with global coverage SIM’s, on a 10 year, 500 MB bundled data plan that is pre-activated and ready to use out of the box.
If your modem did not come with a bundled data plan then you can activate a new Verizon or AT&T data plan by visiting http://go.nimbeLink.com, creating an account, and then activating your NimbeLink there. Alternatively, you can also contact your preferred cellular carrier for assistance in setting up a data plan.

2.2 Access Point Names
Users will need to set an Access Point Name (APN) on their modem for it to be able to connect to a cellular carrier’s network. The APN is determined by the cellular carrier and the type of data plan that is in use.
The table below contains a list of common APNs and their respective carriers. It is important to use the APN that corresponds to the proper carrier. Failure to do so will result in failed cellular network connections. Customers using non- NimbeLink data plans will need to contact their carriers for APN information.

2.3 Development Kit Configuration
This development kit may be used as a stand alone development kit interfaced to a PC or as a shield connected to another development kit with a compatible Arduino shield interface.
The SW1 DIP switch will ship with a piece of tape covering the switches. This should be removed by the user upon getting started with the kit.
2.3.1 USB Interfaces
The development kit has two USB Mini-B connectors to allow for the use of the modem’s serial UART AT command interface and/or the modem’s USB interface.
The J5 USB interface is for connecting to the modem’s USB interface. The USB interface will allow customers to connect to multiple different communication ports on the modem including:

• AT Command interfaces
• Debug interfaces for modem diagnostic tools
• GNSS NMEA streaming interfaces

The specific USB interfaces available will be modem specific and connecting to the USB interface will require that users download the modem’s USB drivers from its product page.
The J14 interface will connect to the modem’s USB to serial UART interface IC to access the modem’s serial UART interface. The USB to serial UART interface IC used on the J14
USB interface is an FTDI FT234XD. The FTDI drivers for the FT234XD are available on FTDI’s website.
2.3.2 UART Selection
The NimbeLink modem’s UART interface is multiplexed to several different interfaces on the development kit to allow for easy interfacing with different host development kits and for accessing it through the USB to serial UART interface (J14).
The USB to serial interface will be automatically selected when a USB connection is powered on J14 and will override the selection switch for the other UART interfaces.
This feature may be bypassed, if desired, by modifying the circuit board.

The interface selection for the Arduino interface is controlled by the switches ARD1 (SW1-1) and ARD2 (SW1-2) on SW1 according to the following logic table:

Below is an image of the switch locations on SW1.

2.3.3 Modem Power On
The development kit can automatically boot the modem when power is applied by turning SW1-3/Auto-ON to the ON position. This will enable the development kit’s built in automatic turn on circuit using a TI TPL5111DDCR (U1). This circuit will toggle the modem’s ON_OFF pin low once for about 8 seconds after the 4.0V supply is applied. The automatic turn on circuit can be enabled or disable based using the SW1-3 DIP switch.

Users may also manually turn the modem on or off by disabling the auto turn on circuit by setting SW1-3 to the off position and then use SW2, labeled “ON BTN” on the circuit board, to manually pulse the modem’s ON_OFF line low.

Users may use SW2 to turn off the modem or to turn the modem back on after a shutdown when the automatic turn on circuit is enabled.

2.4 Connect to a PC
This section will guide users through setting up the SWDK2 and issuing AT commands to a NimbeLink modem. For this demonstration a NL-SW-LTE-QBG96 NimbeLink modem will be used, but users may use any modem that uses the standard NimbeLink interface.
2.4.1 SIM Insertion
Insert the SIM card for the NimbeLink modem into the modem’s 3FF SIM interface located on the bottom side of the modem. The gold contacts on the SIM should be inserted so they are facing the modem’s PCB.
Some NimbeLink modems have onboard Verizon SIMs. If the user is using the onboard SIM for Verizon service this step can be skipped.

2.4.2 Modem Placement and Antenna Connectors
Make sure the NimbeLink is installed in the correct orientation in your host board.
Failure to do so will damage the modem and void the warranty.
NimbeLink modems use U.FL RF connectors for connecting antennas to the modem’s LTE and GNSS RF interfaces. U.FL connectors must be carefully handled to avoid damage and users should always use a U.FL extractor tool for  connecting and disconnecting the U.FL connectors. The U.FL connectors should always be inserted and removed with a force that is perpendicular to the modem.
The NimbeLink modem’s RF interfaces are labeled X1, X2, and X3. Each interface has a specific function as documented below. The locations of the interfaces may change depending on the modem and it is recommended that users  carefully review the modem’s documentation before connecting antennas before powering up the modem.

antenna attached for network connectivity.
X2| LTE Diversity Antenna Interface (RX)| This interface must have an antenna attached for Cat 4+ products for  carrier certification compliance and is strongly recommended for Cat 1+ devices.
X3| GNSS Antenna Interface| Do not connect to cellular antennas. This interface requires the use of  an appropriate GNSS antenna. Review the modem’s datasheet for GNSS antenna guidelines.

Users should not attempt to place the modem in the NimbeLink socket or attach the U.FL connectors while power is applied.
To seat the modem, align the NimbeLink modem’s top side U.FL connectors with the two circles seen on the top of the SWDK2’s NimbeLink socket.
Make sure that the modem’s pins are properly aligned in the NimbeLink socket.
Inserting the modem into the NimbeLink socket incorrectly can damage the modem.

Once the modem is seated users can attach the U.FL connectors. When viewing the development kit from the top, the modem’s U.Fl connectors should be in the middle of the development kit when mounted. An example photo of the  modem placement with the U.FL connectors attached is below:

A common issue is accidentally inserting the modem with pins misaligned by one row.
Check pin alignment BEFORE applying power to prevent modem damage.

2.4.3 Connect LTE Antennas
Connect the cellular antennas to the modem’s X1 and X2 ports (if applicable) via the SMA jack on SWDK2’s U.FL to SMA connectors.
Note: LTE-M modems may have the GNSS X3 connector on the top side of the modem in place of a LTE diversity connector. Do not connect LTE antennas to the X3 GNSS antenna port as this may damage the GNSS interface.
In this example the GNSS interface of the modem is left without an antenna.

2.4.4 Apply Power
The development kit can be powered through the barrel jack connector, J15, or through the Arduino interface’s VIN pin. For this exercise, the development kit should be powered through the board’s barrel jack connector using the provided 12V DC power supply. When power is applied the D4 LED will illuminate.

2.4.5 Connect USB
Connect the USB cable to the SWDK2’s J14 interface.

The J14 interface will connect to the modem’s USB to serial UART interface IC to access the modem’s serial UART interface. The D3 LED will illuminate when USB is connected.
2.4.6 Modem Power On
The development kit can automatically boot the modem when power is applied if the automatic turn on circuit is enabled. Otherwise users should press the ON BTN to turn the modem on. Most modems will turn on with a 1 second press  and hold of the ON BTN, but some modems, such as the TC4EU modem, may require 5 seconds. Please refer to the modem’s datasheet for details on its ON_OFF timing.

2.4.7 AT Commands
Communication with cellular modems over the AT command interfaces is done via AT commands. Modems will typically support many of the 3GPP AT commands for basic functionality along with their own set of module vendor specific  AT commands for checking network connectivity, transferring data, and performing diagnostics. AT commands for each modem are documented in their AT command manual, linked to on their product page.
To send AT commands to the modem open a terminal emulator program, such as Tera Term, to communicate with the modem.
If you do not have a terminal emulator program, you can download Tera Term here: https://ttssh2.osdn.jp/index.html.en
Your PC may have multiple COM ports. Select appropriate USB COM port to communicate with the development kit.

Note: Your device may not show up on the port list due to a missing driver. Refer to Section 2.3.1 for instructions on installing a driver.
You may need to adjust the Serial Settings. These can be accessed in Tera Term by going Setup>Serial Port . They can also be updated in Putty by navigating Connection>Serial. Serial Settings should be as follows (these are the default settings):

2.4.7.1 Test Serial Communication
In the terminal program, type the command: AT
followed by the Enter key, and the terminal should respond with: OK
You may need to turn echo on in order to see what you are typing. If you type the command: AT and do not see it being typed on your screen, hit the Enter key, and type the following command: ATE1 followed by the Enter key, and the terminal program should respond with: OK
Type the following command: AT
to verify you can see the command you are typing. After pressing the Enter key, the terminal program will respond with: OK
2.4.7.2 Enable Verbose Error Mode
On occasion, users may run into an error output where the modem outputs “ ERROR “ to an AT command. Users may enable verbose error mode to see what error code is occurring by issuing the following command: AT+CMEE=2
After pressing the Enter key, the terminal program will respond with: OK
2.4.7.3 Cellular Functionality
Some modems may boot into airplane mode or have their cellular functionality turned off. To verify that the cellular functionality is turned on issue the following command:
AT+CFUN?
followed by the Enter key, and the terminal program should respond with: +CFUN: OK
Where x is the functionality parameter. If it is set to a value other than 1 then the user will need to put the modem back into full functionality mode with the AT+CFUN=1 command.

2.4.7.4 Check SIM Communication
Some modems will support dual SIM interfaces, typically with a solder down SIM on the modem along with the 3FF SIM interface. Users should check the datasheet for their device for instructions on selecting their desired SIM interface.
Verify that the modem can read the SIM card by issuing the AT command for your specific modem family located in the chart below.

NL-SW-LTE-TC4NAG
NL-SW-LTE-TC4APG| AT+ICCID| +CCID: xxxxxxxxxxxxxxxxxxxx OK
NL-SW-LTE-GELS3-x| AT+CCID| +CCID: “xxxxxxxxxxxxxxxxxxxx”,”” OK
NL-SW-LTE-QBG96
NL-SW-LTE-QBG95| AT+QCCID| +QCCID: xxxxxxxxxxxxxxxxxxxx OK
All other modems| AT+CCID| +CCID: xxxxxxxxxxxxxxxxxxxx OK

If the modem responds with ERROR or “+CME ERROR: SIM failure” please check that the SIM is properly seated, that the correct SIM interface is selected(if the modem supports dual SIMs), that cellular functionality is enabled (AT+CFUN=1), and verify that the SIM does not require a PIN. If it still responds with an error, and further assistance is needed, please contact NimbeLink for assistance.

2.4.7.5 PDP Context APN Configuration
Before a modem can communicate on the cellular network it must have its PDP context configured with the APN. Devices using Verizon should have the APN automatically pushed to the device within a few minutes of the first pairing of  the modem and SIM on the network. In the event that this does not occur the APN can be manually set.
Note: If the PDP context is in use by an active connection it can not be modified until the PDP context is deactivated, however if the PDP context is active then this typically indicates the APN is correctly set. To deactivate a PDP context  please see the context activation command for your modem (AT#SGACT for Telit based modems, AT+QIACT for Quectel based modems, AT^SICA for Gemalto based modems, and AT+CGACT for Sierra based modems) or turn off the  cellular TX/RX interface by issuing AT+CFUN=4 on non-Telit based modems.
2.4.7.5.1 Verizon Cat1 + Devices
Verizon LTE Cat 1 or higher devices should use PDP context 3 for their data connections and manual APN configuration. Contexts 1, 2, 4, 5, and 6 are used for other services (SMS, registration, ect…) on Verizon and these PDP contexts should not be altered. Doing so may cause the modem to fail to register with the network.
To manually set the APN follow these steps.
Get a snapshot of the current PDP context APN configurations prior to editing them in case an incorrect setting is entered. Type the command:
AT+CGDCONT?
The modem should respond with:
+CGDCONT: 1,”IPV4V6”,”ims”,””,0,0,0,0
+CGDCONT: 2,”IPV4V6”,”vzwadmin”,””,0,0,0,0
+CGDCONT: 3,”IPV4V6”,”vzwinternet”,””,0,0,0,0
+CGDCONT: 4,”IPV4V6”,”vzwapp”,””,0,0,0,0
+CGDCONT: 5,”IPV4V6”,””,””,0,0,0,1
+CGDCONT: 6,”IPV4V6”,”vzwclass6”,””,0,0,0,0
OK
Issued the following command followed by the enter key to change the APN in the third PDP context:
AT+CGDCONT=3,””,””
Where is IP (for IPV4), IPV4V6, or IPV6 and is the APN provided by your cellular data plan vendor. Most devices should use IPV4V6 for their data plan, but this will depend on what IP type the cellular data plan is configured to support.
Verify that the APN has been changed by checking the PDP context configuration.
Type the command followed by the enter key:
AT+CGDCONT?
The modem should respond with:
+CGDCONT: 1,”IPV4V6”,”ims”,””,0,0,0,0
+CGDCONT: 2,”IPV4V6”,”vzwadmin”,””,0,0,0,0
+CGDCONT: 3,””,””,””,0,0,0,0
+CGDCONT: 4,”IPV4V6”,”vzwapp”,””,0,0,0,0
+CGDCONT: 5,”IPV4V6”,””,””,0,0,0,1
+CGDCONT: 6,”IPV4V6”,”vzwclass6”,””,0,0,0,0
OK
2.4.7.5.2 LTE M1 and Non-Verizon LTE Cat 1+ Device APN Configuration
LTE M1 devices on all carriers and non-Verizon LTE Cat 1+ devices typically use PDP context 1 for their data connections and manual APN configuration.
LTE Cat 1+ non-Verizon devices will need to have their APN manually configured. LTE M1
devices can either have their APN manually entered or be configured to request the APN
from the cellular network each time the modem connects by leaving the APN blank.
Note: Some carrier SIMs may load APNs into the PDP contexts upon boot. These APNs may not be the correct APN for the customer’s data plan and will need to be configured on each boot up.
To manually set the APN follow these steps. Issue the following command followed by the Enter key to change the APN in the first PDP context:
AT+CGDCONT=1,””,””
Where is IP (for IPV4), IPV4V6, or IPV6 and is the APN provided by your cellular data plan vendor. Most devices should use IPV4V6 for their data plan, but this will depend on what IP type the cellular data plan is configured to support.
Verify that the APN has been changed by checking the PDP context configuration. Type the command followed by the enter key:
AT+CGDCONT?
The modem should respond with:
+CGDCONT: 1,””,””,””,0,0,0,0
OK

2.4.7.6 Signal Quality
Cellular modems offer several signal quality metrics for determining if a device has a good, poor, or bad connection with the network. These signal metrics are Received Signal Strength Indicator (RSSI), Reference Signal Received Power  (RSRP), and Reference Signal Received Quality (RSRQ). RSSI measurements are available for 2G, 3G, and 4G connections while RSRP/RSRQ measurements are only available for 4G connections.
These three signal quality metrics differ as follows:

• RSSI is a measurement that looks at the wide band RF power coming into the modem from all sources, including all noise and interference from other sources.
• RSRP looks at the average of the RF power in the passband that the modem and the tower are using to communicate and can be used to determine how good the signal power is between the tower while excluding noise and interference from other sources.
• A poor RSRP signal can indicate that the modem is in a poor coverage zone or there is an issue with the antenna connection.
• RSRQ indicates the quality of the connection between the tower and modem by measuring the quality of a received reference signal sent from the tower to the modem.
• A poor RSRQ signal can be an indication that there is noise interfering with the modem’s communication.

For 4G connections it is best to rely on the RSRQ and RSRP measurements as they provide a more granular perspective on the cellular connection. Applications using 4G devices that have 2G/3G fall back should also check RSSI in  the event the modem falls back to a 2G/3G network.
The table below shows the mapping of signal quality to the returned values from the modem. Devices will typically start seeing some occasional connectivity issues, such as dropped connections, when the signal quality is in the lower end of the “Fair” signal quality range. When the modem is in the poor signal quality range connectivity may be problematic.

To check the RSSI signal quality on a modem issue the following AT command to the modem:
AT+CSQ
Followed by the enter key. The modem should respond with:
+CSQ: , OK
where xx is the signal strength of the antenna, and y is the bit error rate in percent.
Typical values are as follows:

The modem’s bit error rate will only be detectable during data transfers and will be not known when the modem is idle.
To check the RSRP and RSRQ signal quality on your modem, issue the AT command for your specific modem located in the table below: