SFERALABS SCMD30XS Strato Pi CM Duo User Guide
- June 11, 2024
- SFERALABS
Table of Contents
SCMD30XS Strato Pi CM Duo
Strato Pi CM Duo v3 User Guide
December 2022 Revision 030
SCMD30XS Strato Pi CM Duo v3 Solo SCMD30XPL Strato Pi CM Duo v3 3+ Lite
SCMD30XP1 Strato Pi CM Duo v3 3+ 8GB SCMD30XP2 Strato Pi CM Duo v3 3+ 16GB
SCMD30XP3 Strato Pi CM Duo v3 3+ 32GB SCMD30X4L Strato Pi CM Duo v3 4S Lite
SCMD30X41 Strato Pi CM Duo v3 4S 8GB SCMD30X42 Strato Pi CM Duo v3 4S 16GB
SCMD30X43 Strato Pi CM Duo v3 4S 32GB
Safety information Qualified personnel Hazard levels Safety instructions
General safety instructions Battery
Introduction Features Device identification Hardware Setup
Opening the case Closing the case Raspberry Pi Compute Module installation How
to flash the eMMC microSD installation Replacing the RTC backup battery
Terminal block Power supply Dedicated GPIO pins Software installation and
configuration Installing the Strato Pi utility Installing the Strato Pi kernel
module Enabling the second SD interface Installing the Real Time Clock driver
Testing the Real Time Clock Configuring the serial port Using Strato Pi CM Duo
Real Time Clock RS-485 serial port SD matrix USB ports power management Secure
element Push button LED Hardware watchdog Reset cycle
1
4 4 4 5 5 6 7 8 9 10 10 11 11 12 12 13 14 14 15 17 17 17 18 18 18 19 20 20 20
21 23 24 25 25 25 26
Strato Pi CM Duo v3 User Guide
Advanced configuration
26
Block diagram
27
Technical specifications
28
Dimensions
30
Disposal
31
Installation and use restrictions
31
Standards and regulations
31
Safety instructions
31
Set-up
31
Conformity Information
32
EU
32
USA
32
CANADA
33
RCM AUSTRALIA / NEW ZEALAND
33
2
Strato Pi CM Duo v3 User Guide
Be sure to always remove the power supply before inserting or removing the
Raspberry Pi Compute Module from the Strato Pi CM Duo.
Follow all applicable electrical safety standards, guidelines, specifications
and regulations for installation, wiring and operations of
Strato Pi CM Duo. Carefully and fully read this Strato Pi CM Duo user guide
before
installation.
Strato Pi CM Duo is not authorised for use in safety-critical applications
where a failure of the product would reasonably be expected to cause personal
injury or death. Safety-critical
applications include, without limitation, life support devices and systems,
equipment or systems for the operation of nuclear facilities and weapons
systems. Strato is neither designed nor intended for use in critical military
or aerospace applications or environments and for automotive applications or
environment. Customer acknowledges and agrees that any such use of Strato Pi
CM Duo is solely at Customer’s risk, and that Customer is solely responsible
for compliance with all legal and regulatory requirements in connection with
such use.
Sfera Labs S.r.l. may make changes to specifications and product descriptions
at any time, without notice. The product information on the web site or
materials is subject to change without notice.
Please download and read the Sfera Labs Terms and Conditions document available at:
Strato and Sfera Labs are trademarks of Sfera Labs S.r.l. Other brands and
names may be claimed as the property of others.
Copyright © 2019-2022 Sfera Labs S.r.l. All rights reserved.
3
Strato Pi CM Duo v3 User Guide
Safety information
Carefully and fully read this user guide before installation and retain it for
future reference.
Qualified personnel
The product described in this manual must be operated only by personnel
qualified for the specific task and installation environment, in accordance
with all relevant documentation and safety instructions. A qualified person
should be capable of fully identifying all installation and operation risks
and avoid potential hazards when working with this product.
Hazard levels
This manual contains information you must observe to ensure your personal
safety and prevent damage to property. Safety information in this manual are
highlighted by the safety symbols below, graded according to the degree of
danger.
DANGER
Indicates a hazardous situation which, if not avoided, will result in death or
serious personal injury.
WARNING
Indicates a hazardous situation which, if not avoided, may result in death or
serious personal injury.
CAUTION
Indicates a hazardous situation which, if not avoided, can result in minor or
moderate personal injury.
NOTICE
Indicates a situation which, if not avoided, can result in damage of property.
4
Strato Pi CM Duo v3 User Guide
Safety instructions
General safety instructions
Protect the unit against moisture, dirt and any kind of damage during
transport, storage and operation. Do not operate the unit outside the
specified technical data. Never open the housing. If not otherwise specified,
install in closed housing (e.g. distribution cabinet). Earth the unit at the
terminals provided, if existing, for this purpose. Do not obstruct cooling of
the unit. Keep out of the reach of children.
WARNING
Life threatening voltages are present within and around an open control
cabinet. When installing this product in a control cabinet or any other areas
where dangerous voltages are present, always switch off the power supply to
the cabinet or equipment.
WARNING
Risk of fire if not installed and operated properly. Follow all applicable
electrical safety standards, guidelines, specifications and regulations for
installation, wiring and operations of this product. The Raspberry Pi Compute
Module board could generate a substantial amount of heat when the software
forces the CPU and/or GPU to operate at high load levels. Ensure that the
product is properly installed and ventilated to prevent overheat.
NOTICE
The connection of expansion devices to this product may damage the product and
other connected systems, and may violate safety rules and regulations
regarding radio interference and electromagnetic compatibility. Use only
appropriate tools when installing this product. Using excessive force with
tools may damage the product, alter its characteristics or degrade its safety.
5
Strato Pi CM Duo v3 User Guide
Battery
This product uses a small lithium non-rechargeable battery to power its
internal real time clock (RTC).
WARNING
Improper handling of lithium batteries can result in an explosion of the
batteries and/or release of harmful substances. Worn-out or defective
batteries can compromise the function of this product. Replace the RTC lithium
battery before it is completely discharged. The lithium battery must be
replaced only with an identical battery. See the “Replacing the RTC backup
battery” section for instructions. Do not throw lithium batteries into fire,
do not solder on the cell body, do not recharge, do not open, do not short-
circuit, do not reverse polarity, do not heat above 100°C and protect from
direct sunlight, moisture and condensation. Dispose of used batteries
according to local regulations and the battery manufacturer’s instructions.
6
Strato Pi CM Duo v3 User Guide
Introduction
Strato Pi CM Duo is an extremely powerful and compact industrial server based
on the Raspberry Pi Compute Module, suitable for use in professional and
industrial applications where reliability and service continuity are key
requirements, and housed in a compact 2 modules DIN rail case.
It is available in several versions. Strato Pi CM Duo 3+ ships with a
Raspberry Pi Compute Module 3+ (Lite, or 8GB, 16GB and 32GB eMMC versions)
pre-installed. Strato Pi CM Duo 4S ships with a Raspberry Pi Compute Module 4S
(Lite, or 8GB, 16GB and 32GB eMMC versions) pre-installed. Strato Pi CM Duo
Solo doesn’t include the Compute Module and is compatible with all current
versions of the Compute Module: 1, 3, 3 Lite, 3+, 3+ Lite, 4S and 4S Lite.
The information contained in this manual covers all Strato Pi CM Duo versions.
All Strato Pi CM Duo versions are identical, except for the Compute Module
model installed.
This manual generally refers to all products as Strato Pi CM Duo.
7
Strato Pi CM Duo v3 User Guide
Features
Strato Pi CM Duo, all versions:
9-28Vdc power supply, with surge and reverse polarity protection, and 1.1A
resettable fuse
up to 1.9A max continuous current (3A peaks) to the 5V Raspberry Pi Compute
Module power supply input pins (at 24Vdc)
highly accurate real time clock with temperature compensated crystal
oscillator (TCXO) and replaceable CR1220 Lithium / Manganese Dioxide back-up
battery
standard RS-485 interface to the Raspberry Pi serial line, with opto-isolator
and electrostatic discharge protection
10/100 Ethernet port
two USB 2.0 type-A ports, with individual power control and fault detection
dual microSD card architecture. Strato Pi CM routes its two microSD card
holders to the Compute Module through a high-speed switching matrix,
controlled by the on-board micro-controller. Each SD card can be set as the
boot card, with the other available as additional storage. This enables for
separate OS/data storage, SD redundancy and infield full-system upgrades. The
microSD slots are hidden, and can be accessed opening the case
hardware watchdog implemented in the Strato Pi CM Duo micro-controller, fully
independent from the Raspberry Pi Compute Module, controlled via the GPIO pins
of the Raspberry Pi board and acting on the Raspberry Pi Compute Module
hardware reset line. The hardware watchdog can also control the microSD switch
matrix, swapping the boot card in case the watchdog is triggered
integrated boot loader for the Strato Pi micro-controller, allowing in-field
firmware upgrades directly from the Raspberry Pi
embedded Microchip ATECC608 secure element chip
front-panel LEDs for power supply, serial line activity, and one GPIO-
controlled LED
recessed push-button, hidden behind the front-panel, connected to a GPIO pin
power supply and serial connections on a pluggable terminal block
packaged in a compact 2 modules DIN rail case.
Strato Pi CM Duo Solo:
compatible with Raspberry Pi Compute Module 1, Raspberry Pi Compute Module 3,
Raspberry Pi Compute Module 3 Lite, Raspberry Pi Compute Module 3+ 8GB,
Raspberry Pi Compute Module 3+ 16GB, Raspberry Pi Compute Module 3+ 32GB,
Raspberry Pi Compute Module 3+ Lite, Raspberry Pi Compute Module 4S 8GB,
Raspberry Pi Compute Module 4S 16GB, Raspberry Pi Compute Module 4S 32GB,
Raspberry Pi Compute Module 4S Lite
Strato Pi CM Duo 3+:
pre-installed and tested Raspberry Pi Compute Module 3+, Lite, 8GB, 16GB or
32GB eMMC versions.
8
Strato Pi CM Duo v3 User Guide
Strato Pi CM Duo 4S: pre-installed and tested Raspberry Pi Compute Module 4S,
Lite, 8GB, 16GB or 32GB
eMMC versions
Device identification
The device can be identified with the information provided in the rating and
identification plate, permanently attached to the side of the case.
EXAMPLE RATING AND IDENTIFICATION PLATE
9
Strato Pi CM Duo v3 User Guide
Hardware Setup
STRATO PI CM DUO CONNECTION DIAGRAM
For the initial set-up, the plastic DIN rail must be removed to access the
circuit boards and internal connectors. The case also needs to be opened if
the factory configuration of the RS-485 termination resistors must be changed
(see below).
NOTICE
Before opening the Strato Pi CM Duo case, disconnect all power sources and any
connection to external devices, including USB and Ethernet cables.
Opening the case
Follow these steps, in the exact order, to open the case: 1. Remove the green
pluggable terminal block 2. Remove the black plastic DIN rail hook 3. With a
small flat screwdriver gently separate the bottom case and boards assembly
from the top cover; lift the side next to the DIN rail hook first 4. The
circuit boards assembly will simply slide out of the case, as it is
mechanically held
in place by the bottom case only
10
Strato Pi CM Duo v3 User Guide
Closing the case
5. Replace the circuit boards assembly inside the case; ensure that the
USB/Ethernet connectors are aligned with the opening in the case
6. Replace the case bottom, inserting the side opposite to the DIN rail hook
first, then gently push the other side in place
7. Replace the black plastic DIN rail hook.
OPENING AND CLOSING THE CASE
Raspberry Pi Compute Module installation
To install your own Compute Module in Strato Pi CM Duo Solo, or replace the
pre-installed module, no tools are required. The Compute Module fits in a
standard 200 pin DDR2 SODIMM (JEDEC MO-224 mechanical specification) slot.
NOTICE
Static electricity can damage the components in your system. To protect your
system’s components from static damage during the installation process, touch
any of the unpainted metal surfaces on your computer’s frame or wear an ESD
wrist strap before handling internal components. Either method will safely
discharge static electricity that’s naturally present in your body. When
handling the Raspberry Pi Compute Module, be sure to hold it along the side
edges using your thumb and index finger. Avoid touching the components and pin
connectors as damage can occur. Align the notches on the Compute Module with
the ridges in the DDR2 slot. Insert the module using firm and even pressure,
and push down on the module until the clips on the side of the slot snap into
place.
11
Strato Pi CM Duo v3 User Guide
How to flash the eMMC
In order to flash the Compute Module’s eMMC memory, an additional board, like
the Compute Module IO Board V3, shall be used. Use the latest RPIBOOT utility
from Raspberry Pi and refer to its documentation1 for installation and usage
details.
Alternatively, if using the Compute Module 4S (or a Compute Module 3/3+ with
USB host boot mode previously enabled2) you can boot the unit from USB3,
access via SSH, and flash the eMMC which will be available as a local mass
storage device.
microSD installation
Strato Pi CM Duo has two microSD slots to install flash memory cards.
When the Compute Module Lite is installed, as it lacks an internal eMMC chip,
one of the two microSD slots will be used as the boot SD card, just like with
a Raspberry Model B board. The other microSD can be used as additional
storage. Dedicated commands to the micro-controller allow to select which slot
is used for boot, and if the other is enabled or not.
When a Compute Module with embedded eMMC is installed, both microSD slots can
be used as additional storage. You can only access one SD card at a time, but
the active card can be selected sending the appropriate commands to the micro-
controller.
The microSD slots are not directly accessible with the case closed. The slots
are located on the vertical board, next to the USB/Ethernet modular connector.
The bottom slot is SDA, and the top is SDB.
MICRO SD SLOTS
1 https://www.raspberrypi.com/documentation/computers/compute-module.html
flashing-thecompute-module-emmc
2 https://www.raspberrypi.com/documentation/computers/raspberry-pi.html#usb-
host-boot-mode
3 https://www.raspberrypi.com/documentation/computers/raspberry-pi.html
booting-from-usbmass-storage
12
Strato Pi CM Duo v3 User Guide
Replacing the RTC backup battery
Strato Pi CM Duo has a hardware real time clock with a dedicated long-life
nonrechargeable back-up battery.
Strato Pi CM Duo is shipped with a CR12204 Lithium / Manganese Dioxide
(Li/MnO2) battery installed.
The battery is only used to power the RTC chip when the main power is not
available. Depending on operating conditions it should last up to two years if
the Strato Pi CM Duo is not powered, more if it regularly receives external
power.
The RTC backup battery holder is on the vertical circuit board, opposite the
Compute Module slot. In the Strato Pi CM Duo, the battery is not accessible
from the outside. You should first remove the case body to gain access to the
Strato Pi CM Duo circuit boards. Follow the procedure described at the
beginning of this chapter to open and replace the case.
WARNING
Improper handling of lithium batteries can result in an explosion of the
batteries and/or release of harmful substances.
Worn-out or defective batteries can compromise the function of this product.
KEEP OUT OF REACH OF CHILDREN. Swallowing may lead to serious injury or death
in as little as 2 hours due to chemical burns and potential perforation of the
esophagus. Immediately see doctor.
Replace the RTC lithium battery before it is completely discharged. Replace
the battery every 5 years even if the battery is still working properly. The
lithium battery must be replaced only with an identical CR1220 or BR1220
battery.
Do not throw lithium batteries into fire, do not solder on the cell body, do
not recharge, do not open, do not short-circuit, do not reverse polarity, do
not heat above 100°C and protect from direct sunlight, moisture and
condensation.
Dispose of used batteries according to local regulations and the battery
manufacturer’s instructions.
NOTICE
Before opening the Strato Pi CM Duo case, disconnect all power sources and any
connection to external devices, including USB cables.
Use a non-conductive pin or small tool to help extract the battery from its
holder. Insert the new battery with a gentle push. You don’t need tools to
insert the battery. The battery is held into place by a spring contact.
4 BR1220 batteries (Lithium Poly-carbonmonofluoride) can also be used, for improved shelf and service life.
13
Strato Pi CM Duo v3 User Guide
Be sure to insert the battery so that the negative (-) terminal is facing the
vertical circuit board, and touches the contact pad at the center of the
battery holder, as shown in the photo below.
Reversing the battery polarity may damage the product.
The real time clock will reset its time immediately when the RTC backup
battery is disconnected.
RTC BACKUP BATTERY HOLDER
RTC BACKUP BATTERY INSTALLED
Terminal block
Strato Pi CM Duo has a 5 positions terminal block for power and serial
connections.
The maximum conductor cross section is 1.5 mm2 (16 AWG), or 0.5 mm2 when using
ferrules (highly recommended). Recommended stripping length is 5 mm. Screw
thread is M2. Never exceed 0.25 Nm torque when tightening the screws.
Power supply
Strato Pi CM Duo can be powered with DC voltage only: DC: nominal voltage
range 9V to 28.0V. Respect the correct polarity shown in the schematic diagram
(+ -). The power supply circuit implements reverse polarity protection using
an auto resetting fuse and surge protection up to ±1000V/2ohms 1.2/50s.
14
Strato Pi CM Duo v3 User Guide
A blue on-board LED, also visible through the front panel of the DIN rail
case, is lit when power supply is available. This LED also blinks while the
Compute Module boot process is in progress.
The Strato Pi CM Duo power supply stage is optimised to deliver up to 1.9A at
5V to the Raspberry Pi Compute Module.
The voltage regulator can supply up to 3.0A 5V output short duration current
peaks (<1sec).
Because Strato Pi CM Duo has a 1.1A resettable fuse (polyfuse) on the power
supply line, the maximum current that its regulator can deliver is also
limited by this fuse, and depends on the input voltage.
The following table lists the typical measured output current of the power
supply stage at different input voltages, and the corresponding input current.
At high input voltage levels, the voltage regulator’s thermal protection
becomes the limiting factor.
STRATO PI CM DUO POWER SUPPLY STAGE TYPICAL IN/OUT VOLTAGE AND CURRENT5
Dedicated GPIO pins
Strato Pi CM Duo uses some of the Raspberry Pi Compute Module GPIO pins. These
pins should not be used for other functions.
GPIO pin GPIO2/SDA GPIO3/SCL GPIO14/TXD GPIO15/RXD
Direction
out in
Description I2C SDA line for the real time clock I2C SCL line for the real
time clock
serial TX line serial RX line
5 FUSE marks the level where the polyfuse opens to limit input current; REG is the voltage regulator’s thermal protection limit.
15
Strato Pi CM Duo v3 User Guide
GPIO pin GPIO32 GPIO39 GPIO17 GPIO18 GPIO16 GPIO38 GPIO37 GPIO33 GPIO30 GPIO0 GPIO31 GPIO1 GPIO6 GPIO34
Direction out out in out out in out in out in out in out
in/out
Description cycle high/low for watchdog heartbeat
set to high to enable the watchdog high on watchdog timeout
set to high to enable the shutdown cycle set to high to turn on LED L1 high
when P1 button pressed
soft serial TX for Strato MCU configuration soft serial RX for Strato MCU
configuration set to low to enable USB1 (bottom) power
low on USB1 fault set to low to enable USB2 (top) power
low on USB2 fault expansion bus enable (reserved for future use) expansion bus
aux/act line (reserved for future use)
16
Strato Pi CM Duo v3 User Guide
Software installation and configuration
All features of Strato Pi CM Duo are controlled via dedicated GPIO, the I2C
bus and a soft serial RX/TX interface to the embedded micro-controller and can
be used with most operating systems and programming languages.
The following software installation notes are based on the Raspberry Pi OS
(formerly Raspbian) operating system.
Installing the Strato Pi utility
The Strato Pi utility is a simple command-line script to control some of
Strato Pi’s basic functions.
Run the following commands to download and install the Strato Pi utility:
$ cd /usr/local/bin $ sudo wget http://sferalabs.cc/files/stratocmduo/strato $
sudo chmod 755 strato
You can run the Strato Pi utility without arguments to print its options:
$ strato Usage: strato led on|off|length_millis|length_millis pause_millis
repeats
strato usb1|usb2 on|off|fault strato expbus on|off strato watchdog
enable|disable|heartbeat|timeout strato reset
All commands should be run as superuser, so always use sudo to run strato.
Installing the Strato Pi kernel module
The Strato Pi kernel module can be used to easily access Strato Pi CM Duo’s
features via sysfs file system.
Refer to the following instructions to download and install the module or go
to:
https://github.com/sfera-labs/strato-pi-kernel-module
for updated instructions, usage details and examples.
Download and install:
$ sudo apt install git raspberrypi-kernel-headers $ git clone –depth 1
–recursive https://github.com/sfera-labs/strato-pikernel-module.git $ cd
strato-pi-kernel-module $ make $ sudo make install $ dtc -@ -Hepapr -I dts -O
dtb -o stratopi.dtbo stratopi.dts $ sudo cp stratopi.dtbo /boot/overlays/
Add the following line to /boot/config.txt:
dtoverlay=stratopi
Optionally, to be able to use the sysfs files not as super user, create a new
group “stratopi” and set it as the module owner group by adding an udev rule:
$ sudo groupadd stratopi
17
Strato Pi CM Duo v3 User Guide
$ sudo cp 99-stratopi.rules /etc/udev/rules.d/
and add your user to the group, e.g., for user “pi”:
$ sudo usermod -a -G stratopi pi
Reboot:
$ sudo reboot
You will find the directory /sys/class/stratopi/ which gives you access to
Strato Pi CM Duo’s functionalities.
Enabling the second SD interface
The SD1 interface must be enabled with the following line in the
/boot/config.txt file:
dtoverlay=sdio,bus_width=4,poll_once=off
Installing the Real Time Clock driver
The RTC is based on the NXP PCF2131 RTC module and is connected to the
Raspberry Pi via its I2C serial bus. Refer to the following instructions to
download and install the module or go to: https://github.com/sfera-labs/rtc-
pcf2131 for updated instructions. Download and install:
$ sudo apt install git raspberrypi-kernel-headers $ git clone –depth 1
https://github.com/sfera-labs/rtc-pcf2131 $ cd rtc-pcf2131 $ make $ sudo make
install $ dtc -@ -Hepapr -I dts -O dtb -o rtc-pcf2131.dtbo rtc-pcf2131.dts $
sudo cp rtc-pcf2131.dtbo /boot/overlays/
Add the following line to /boot/config.txt:
dtoverlay=rtc-pcf2131
Reboot:
$ sudo reboot
Testing the Real Time Clock
Assuming you are connected to the Internet and your Pi was able to reach a
public NTP (Network Time Protocol) server, you should see the current date and
time using the “date” command:
$ date Thu Dec 10 18:02:32 CET 2015
Also check the date and time stored in the hardware clock:
$ sudo hwclock -r Thu 10 Dec 2015 06:03:01 PM CET -0.546570 seconds
18
Strato Pi CM Duo v3 User Guide
If the returned date and time is not correct, or “hwclock” returns an error,
use the “-w” option to set the hardware clock to the current time:
$ sudo hwclock -w
Then recheck the time stored in the hardware clock to ensure it matches.
Configuring the serial port
By default, the Linux serial console is active on the main UART
(/dev/ttyAMA0). If you are using the RS-485 interface for your applications,
you should disable it to avoid console data being sent to the serial port. To
disable the ttyAMA0 console service, run:
$ sudo systemctl disable serial-getty@ttyAMA0.service
and edit the /boot/cmdline.txt file to delete the serial console
configuration:
console=serial0,115200
19
Strato Pi CM Duo v3 User Guide
Using Strato Pi CM Duo
Real Time Clock
Strato Pi CM Duo has a hardware real time clock with a dedicated long-life
nonrechargeable back-up battery.
Once the RTC driver is properly installed, you will simply use the date and
time commands to control the hardware clock.
RS-485 serial port
Strato Pi CM Duo uses the Raspberry Pi standard UART TX/RX pins on the GPIO
connector to implement a standard RS-485 port.
The RS-485 port is isolated from the Raspberry Pi’s serial lines using
dedicated optocouplers and from the main power supply with a high-efficiency
DC-DC converter. This configuration should prevent ground loops between
devices connected through the serial line.
The RS-485 TX/RX switching is implemented automatically in the Strato Pi’s
microcontroller, based on speed and number of bits detection, and is
completely transparent to the software controlling the UART on Raspberry Pi.
It can also be manually configured to work with fixed communication parameters
(speed, bits, parity, stop bits) or in passive mode (refer to the “Strato Pi
Logic Controller Advanced Configuration Guide” document for additional
information).
The RS-485 line has 620 Ohm pull-up and pull-down resistors on lines A and B.
The biasing resistors ensure that, during idle periods the data lines are kept
at a stable voltage level and prevent false triggering of receiver input.
These resistors can be disabled by removing jumpers JP1 and JP2 respectively.
A 100 Ohm termination resistor between A and B is connected when the J1 micro-
switch is moved toward the terminal block.
RS-485 JUMPERS AND SWITCH SCHEMATIC
20
Strato Pi CM Duo v3 User Guide
RS-485 JUMPERS AND SWITCH POSITION
SD matrix
Strato Pi CM Duo implements a flexible dual microSD card architecture.
Strato Pi CM routes its two microSD card holders to the Compute Module through
a highspeed switching matrix, controlled by the on-board micro-controller.
Each SD card can be set as the boot card, with the other available as
additional storage.
This enables for separate OS/data storage, SD redundancy and in-field full-
system upgrades.
The BCM283x in the Raspberry Pi Compute Module supports two SD card
interfaces, SD0 and SD1.
The first (SD0) is a proprietary Broadcom controller that does not support
SDIO and is the primary interface used to boot and talk to the eMMC or SDX
signals. The CM will always try to boot from this interface first.
The second interface (SD1) is standards compliant and can interface to SD,
SDIO and eMMC devices.
Both interfaces can support speeds up to 50MHz single ended (SD High Speed
Mode), and this speed is supported by the Strato Pi CM Duo SD matrix as well.
Strato Pi CM Duo has two microSD slots, called SDA (bottom) and SDB (top), and
the SD matrix allows 2×2 connections between both SDX/SD1 interfaces and the
SDA/SDB slots.
NOTICE
Disconnecting an SD card from the Compute Module’s SD interfaces when partitions from the card are mounted at the operating system level, can result in file system and data
21
Strato Pi CM Duo v3 User Guide
corruption. The Strato Pi matrix and the micro-controller don’t check for card
usage and don’t provide any safety mechanism to prevent improper disconnection
of the SD cards.
The matrix is controlled by three I/O lines of the Strato Pi micro-controller:
RA5 (SDX enable), RC0 (SD1 enable) and RA4 (SDA/SDB switch). These lines are
managed using the micro controller serial protocol and the Strato Pi kernel
driver for Linux. The matrix has a hardware default configuration so that,
when the micro-controller lines are highimpedance, it has a stable
configuration, with SDX connected to SDA and SD1 not connected.
SD MATRIX DEFAULT CONFIGURATION
With SDA used as the boot card, SDB can be connected to the SD1 interface, and
used as additional storage.
SD MATRIX BOOT FROM SDA AND SDB ENABLED FOR ADDITIONAL STORAGE
The SDX interface can be connected to SDB instead of SDA, so that boot will be
done from SDB.
22
Strato Pi CM Duo v3 User Guide
SD MATRIX BOOT FROM SDB
Finally, with the SDX interface connected to SDB for boot, the SDA slot can be
enabled to be used for additional storage.
SD MATRIX BOOT FROM SDB AND SDA ENABLED FOR ADDITIONAL STORAGE
It is also possible to disable both the SDX and SD1 interfaces. This
configuration could be used with the Compute Module versions that have the
embedded eMMC storage, when no external SD card is needed.
USB ports power management
Strato Pi CM Duo has two USB ports, USB1 (bottom) and USB2 (top).
USB PORTS
23
Strato Pi CM Duo v3 User Guide
Both ports are individually controlled by a dedicated power switch with over-
current protection. The power switch is internally current limited and has
thermal shutdown that protects the device and load. A fault status output flag
is asserted during over-current and thermal shutdown conditions. The power-
enable inputs and the fault status outputs are routed to the Raspberry Pi’s
GPIO lines to easily control and monitor connected USB devices from your
application. Power is on by default. GPIO30 and GPIO31 control power to USB1
and USB2 respectively. Set GPIO30/31 low to enable power to USB1/2, or high to
remove power. The Strato Pi utility offers commands to control the USB ports
power state. USB1 on:
$ sudo strato usb1 on
USB1 off:
$ sudo strato usb1 off
GPIO0 and GPIO1 return the fault state of USB1 and USB2. These lines will be
high in normal conditions, or low when a fault is present. Print “1” if there
is a fault on USB2, “0” if not:
$ sudo strato usb2 fault; echo $?
Secure element
Strato Pi CM Duo embeds the ATECC608A or ATECC608B (depending on production
lot) secure element chip from Microchip. The chip is connected to the
Raspberry Pi Compute Module via the I2C bus (default address: 0x60). Its key
features are: Cryptographic co-processor with secure hardware-based key
storage Protected storage for up to 16 Keys, certificates or data Hardware
support for asymmetric sign, verify, key agreement ECDSA: FIPS186-3
Elliptic Curve Digital Signature ECDH: FIPS SP800-56A Elliptic Curve Diffie-
Hellman NIST standard P256 elliptic curve support
Hardware support for symmetric algorithms SHA-256 & HMAC hash including off-
chip context save/restore AES-128: encrypt/decrypt, Galois field multiply for
GCM
Networking key management support Turnkey PRF/HKDF calculation for TLS 1.2 &
1.3 Ephemeral key generation and key agreement in SRAM Small message
encryption with keys entirely protected
Secure boot support
24
Strato Pi CM Duo v3 User Guide
Full ECDSA code signature validation, optional stored digest/signature
optional communication key disablement prior to secure boot
Encryption/Authentication for messages to prevent on-board attacks Internal
high-quality FIPS 800-90 A/B/C Random Number Generator (RNG) Two high-
endurance monotonic counters Guaranteed unique 72-bit serial number.
Push button
There is a recessed push button that is easily accessible removing the front
panel. When this button is pressed, the Strato Pi CM Duo controller will set
GPIO38 high, so that an application can easily detect it by simply polling
this GPIO line.
LED
Strato Pi CM Duo has an on-board LED that can be controlled using GPIO16.
Simply set GPIO16 high to turn on the LED. The Strato Pi utility offers
commands to control the LED. LED on continuously:
$ sudo strato led on
LED off:
$ sudo strato led off
LED on for 500 milliseconds:
$ sudo strato led 500
LED on for 500 milliseconds, followed by 100 milliseconds off, repeated three
times:
$ sudo strato led 500 100 3
Hardware watchdog
Strato Pi CM Duo implements a dedicated hardware watchdog circuit that can be
used to perform the hardware reset of the Raspberry Pi Compute Module.
Being controlled by Raspberry Pi’s GPIO pins, it is extremely easy to control
watchdog operation using simple custom scripts in your application.
The watchdog can also swap the boot SD card after one or more consecutive
watchdog timeouts, to automatically recover from SD cards failures.
Watchdog default behavior is described below, but all timing parameters and
control logic can be modified as described in the “Strato Pi Logic Controller
Advanced Configuration Guide” document.
The watchdog is normally disabled. To enable it, set GPIO39 pin to high. While
GPIO39 is high, the Strato Pi CM Duo controller will watch for state changes
of the GPIO32 heartbeat
25
Strato Pi CM Duo v3 User Guide
pin. You should ensure that GPIO32 flips its state between high and low faster
than every 60 seconds. If the Strato Pi CM Duo controller doesn’t see GPIO32
changing state for more than 60 seconds, it will initiate a shutdown
procedure, rising the GPIO17 timeout pin to high, to signal that a watchdog
timeout has occurred. If possible, you should immediately initiate a software
shutdown on Raspberry Pi Compute Module, and set the GPIO18 shutdown pin to
high. When GPIO18 is set to high or 60 seconds after the timeout, Strato Pi CM
Duo will wait 60 seconds more, then reset the Raspberry Pi Compute Module
(pulling the RUN line low). Note that Strato Pi CM Duo will reset the
Raspberry Pi Compute Module even if GPIO18 is not set high. In this case the
power cycles occurs 120 seconds after the heartbeat timeout. The Strato Pi
utility can be used to control the watchdog from your own application. Enable
the watchdog:
$ sudo strato watchdog enable
Disable the watchdog:
$ sudo strato watchdog disable
Send the heartbeat:
$ sudo strato watchdog heartbeat
Print “1” if the watchdog timeout is expired, “0” if not:
$ sudo strato watchdog timeout; echo $?
Reset cycle
You can start a delayed reset cycle by rising Raspberry Pi’s GPIO18 pin. When
GPIO18 is set to high, Strato Pi CM Duo will wait 60 seconds and then reset
the Raspberry Pi Compute Module.
To initiate a delayed reset cycle:
$ sudo strato reset
Advanced configuration
The Strato Pi CM Duo logic controller can be configured from the Raspberry Pi
to change the default behavior and timing of the hardware watchdog and reset
features. The RX/TX switching mode (TX-Enable control) of the RS-485 serial
port is also configurable. These configuration parameters can be accessed
using the Strato Pi kernel module or implementing the underlying ASCII-based
serial protocol described in the “Strato Pi Logic Controller Advanced
Configuration Guide” document.
26
Strato Pi CM Duo v3 User Guide
Block diagram
STRATO PI CM DUO BLOCK DIAGRAM
27
Strato Pi CM Duo v3 User Guide
Technical specifications
Power supply
Current consumption at VS+ 12 V including Raspberry Pi CM 3+ Lite, with
Ethernet and RS-485 connected, no USB devices Current consumption at VS+ 24 V
including Raspberry Pi CM 3+ Lite, with Ethernet and RS-485 connected, no USB
devices Raspberry platform compatibility
Serial communication port Serial port baud rates ESD-Protection voltage on
RS-485 A/B Surge protection on RS-485 A/B Fail safe feature on RS-485 USB
ports current limit (each port) Real time clock Housing
Electromagnetic immunity compliance
Operating temperature
dc 24 V nominal (range 9-28 V), max 1.1 A
Reverse polarity protection with 1.1 A resettable fuse
low CPU load: 170 mA 100% CPU load: 410 mA
Actual current consumption may vary based on working conditions
low CPU load: 100 mA 100% CPU load: 220 mA
Actual current consumption may vary based on working conditions
Raspberry Pi Compute Module 1 Raspberry Pi Compute Module 3 Raspberry Pi
Compute Module 3 Lite Raspberry Pi Compute Module 3+ 8GB Raspberry Pi Compute
Module 3+ 16GB Raspberry Pi Compute Module 3+ 32GB Raspberry Pi Compute Module
3+ Lite Raspberry Pi Compute Module 4S 8GB Raspberry Pi Compute Module 4S 16GB
Raspberry Pi Compute Module 4S 32GB Raspberry Pi Compute Module 4S Lite
RS-485 Half-Duplex with automatic data direction management
1200 to 115200
±15 kV human body model ±8 kV contact discharge
Surge protection up to ±500 V / 2 Ohms 1.2/50 s; 600 W peak pulse power
capability at 10/1000 s waveform
Yes
0.5 A (min.)
Internal RTCC circuit with backup lithium battery. Only use CR1220 or BR1220
batteries.
Expected battery life without main power supply: ~2 years
standard 2M for DIN rail
EN 61000-4-2 (ESD) EN 61000-4-3 (Radiated RF Field) EN 61000-4-4 (Burst/fast
transient) EN 61000-4-5 (Surge) EN 61000-4-6 (Conducted) EN 61000-4-8 (Power
frequency magnetic field) CM1, CM3: -20…+50 °C CM3+, CM4S: -20…+60 °C
28
Strato Pi CM Duo v3 User Guide
Storage temperature Altitude Humidity Protection degree Weight
-30…+80 °C Up to 2000 m 5% to 95% RH noncondensing IP20 160 g (including Raspberry Pi Compute Module)
29
Strato Pi CM Duo v3 User Guide
Dimensions
DIMENSIONS (mm)
30
Strato Pi CM Duo v3 User Guide
Disposal
Waste Electrical & Electronic Equipment (Applicable in the European Union and
other European countries with separate collection systems). This marking on
the product, accessories or literature indicates that the product should not
be disposed of with other household waste at the end of their working life. To
prevent possible harm to the environment or human health from uncontrolled
waste disposal, separate these items from other types of waste and recycle
them responsibly to promote the sustainable reuse of material resources.
Household users
should contact either the retailer where they purchased this product, or their
local government office, for details of where and how they can take these
items for environmentally safe recycling. This product and its electronic
accessories should not be mixed with other commercial wastes for disposal.
Strato Pi CM Duo contains a small non rechargeable manganese dioxide lithium
coin battery. In the Strato Pi CM Duo, the battery is not accessible from the
outside. You should first remove the case body to gain access to the Strato Pi
CM Duo circuit board. Always remove the battery before disposing of this
product.
Installation and use restrictions
Standards and regulations
The design and the setting up of electrical systems must be performed
according to the relevant standards, guidelines, specifications and
regulations of the relevant country. The installation, configuration and
programming of the devices must be carried out by trained personnel. The
installation and wiring of connected devices must be performed according to
the recommendations of the manufacturers (reported on the specific data sheet
of the product) and according to the applicable standards. All the relevant
safety regulations, e.g. accident prevention regulations, law on technical
work equipment, must also be observed.
Safety instructions
Carefully read the safety information section at the beginning of this
document.
Set-up
For the first installation of the device proceed according to the following
procedure: make sure all power supplies are disconnected install and wire the
device according to the schematic diagrams on the specific product
user guide
31
Strato Pi CM Duo v3 User Guide
after completing the previous steps, switch on the power supply and other
related circuits.
Conformity Information
EU
This device complies with the following applicable European Community
harmonised standards: 2014/30/EU – Electromagnetic Compatibility Directive
(EMC) 2011/65/EU and 2015/863/EU – Restriction of the use of certain hazardous
substances
in electrical and electronic equipment (RoHS) The following harmonised
standards have been used to demonstrate conformity to these directives:
EN61000-6-2:2019 – EMC Immunity standard for industrial environments EN
61000-6-3:2007/A1:2011/AC:2012 – EMC Emission standard for residential,
commercial and light-industrial environments The declaration of conformity is
available on the internet at the following address: https://www.sferalabs.cc
USA
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 or more
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. Shielded cables must be used with this equipment to
maintain compliance with FCC regulations. 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.
32
Strato Pi CM Duo v3 User Guide
CANADA
This Class B digital apparatus complies with Canadian ICES-003. Cet appareil
numérique de la classe B est conforme à la norme NMB-003 du Canada.
RCM AUSTRALIA / NEW ZEALAND
This product meets the requirements of the standard EN 61000-6-3:2007/A1:2011/
AC:2012 – Emission for residential, commercial and light-industrial
environments.
33
Strato Pi CM Duo v3 User Guide
References
- sferalabs.cc/files/stratocmduo/strato
- GitHub - sfera-labs/rtc-pcf2131: Driver for NXP PCF2131 RTC
- GitHub - sfera-labs/strato-pi-kernel-module: Strato Pi driver kernel module
- Raspberry Pi Documentation - Compute Module hardware
- Raspberry Pi Documentation - Raspberry Pi hardware
- Raspberry Pi Documentation - Raspberry Pi hardware
- Sfera Labs