IOT-LINK: Linux: How-To Guide - Revision history

Igor at 13:30, 16 February 2026

2026-02-16T13:30:07Z

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Igor: /* Digital I/O */

2026-01-21T15:03:43Z

‎Digital I/O

Igor: /* Cellular Modem */

2025-09-21T13:52:07Z

‎Cellular Modem

Igor: Igor moved page IOT-LINK: Debian Linux: How-To Guide to IOT-LINK: Linux: How-To Guide

2025-09-04T12:25:28Z

Igor moved page IOT-LINK: Debian Linux: How-To Guide to IOT-LINK: Linux: How-To Guide

Igor: /* Cellular Modem */

2025-08-21T12:35:07Z

‎Cellular Modem

Igor: Created page with "= Overview = The default run-time Linux filesystem image for the CompuLab IOT-LINK Internet of Things Gateway is based on Debian GNU/Linux BookWorm. The default Debian Linux i..."

2025-06-10T11:44:34Z

Created page with "= Overview = The default run-time Linux filesystem image for the CompuLab IOT-LINK Internet of Things Gateway is based on Debian GNU/Linux BookWorm. The default Debian Linux i..."

New page

= Overview =
The default run-time Linux filesystem image for the CompuLab IOT-LINK Internet of Things Gateway is based on Debian GNU/Linux BookWorm.
The default Debian Linux image includes the following packages:

* Core system
* Debian package management system
* SSH server and client
* NetworkManager
* ModemManager
* Bluez5 Bluetooth tools and daemons
* Docker

= Serial Console =
IOT-LINK provides a serial console on the front panel micro-USB '''DBG''' connector.
== Connecting to a host PC ==
# Use a micro-USB cable to connect the Console connector to a USB port on your host PC.
# Make sure the CP2104 driver is available with your operating system, otherwise install it from https://www.silabs.com/documents/public/software/CP210x_Windows_Drivers_with_Serial_Enumeration.zip
# Identify the host PC interface and port number that will be used for communication with the device:
#* In most Linux PCs, the serial port will be denoted as one of the following: /dev/ttyUSB0, /dev/ttyUSB1 ... /dev/ttyUSBn (where n is a positive integer)
#* In Windows PCs, the serial port usually will be denoted as one of the following: COM1, COM2 ... COMn (where n is a positive integer)
# Start a terminal emulation program (such as [https://www.putty.org/ PuTTY] on Windows or minicom on Linux).
# In the port configuration section of the program select the previous identified port and set the following serial port parameters:
<blockquote>
{{:SB-SOM: serial port parameters table}}
</blockquote>

= Connection and Login =
This Debian rootfs comes with a default sudo user ''compulab''.
User password has to be set at the very first login.

<pre>
Compulab Release iot-link 1.0 25.05 based on
Debian GNU/Linux 12 iot-link ttyLP0

iot-link login: compulab
You are required to change your password immediately (administrator enforced).
New password:
Retype new password:
</pre>

To login into the Linux system, use a terminal emulator as described [[IOT-LINK: Debian Linux: How-To Guide#Serial Console|here]], or connect through the network (ssh).

= Package Management =
The IOT-LINK Debian Linux image includes everything required to use the Debian package management utilities. 
Use [http://linux.die.net/man/8/apt apt] and [https://linux.die.net/man/1/dpkg dpkg] for managing software packages.

= Device Serial Number and Configuration =
Product information is stored in on-board EEPROM. 
* To read the product serial number, issue the following command:
cat /proc/device-tree/baseboard-sn

'''Note''' "-" sign which appears on the label is intentionally replaced by "0"

* To read the product configuration part number, issue the following command:
cat /proc/device-tree/baseboard-options


= Docker =
The [https://docs.docker.com/engine/ Docker Engine] is preinstalled.
* The following command downloads a test image and runs it in a container. The container sample prints a message and exits.
<pre>
sudo docker run -it ubuntu
latest: Pulling from library/ubuntu
aa21f24e1940: Pull complete
...
Digest: sha256:e3f92abc0967a6c19d0dfa2d55838833e947b9d74edbcb0113e48535ad4be12a
Status: Downloaded newer image for ubuntu:latest
root@0d6b133a7a93:/# cat /etc/issue
Ubuntu 24.04 LTS \n \l
</pre>

= Cellular Modem =
IOT-LINK cellular interface is implemented with a mini-PCIe cellular modem and a micro-SIM socket.
*Cellular module is an option that can be pre-installed into the gateway. Verify your gateway is assembled with the modem module
*To set up IOT-LINK for cellular functionality, install an active SIM card into SIM socket located behind the back panel. Please refer to [https://www.compulab.com/products/iot-gateways/iot-link-industrial-iot-gateway/#devres IOT-LINK reference guide] for details. 
*Cellular antenna should be connected to SMA connector '''A''' on the front panel.
== Cellular Connection ==
Get IP:
sudo dhclient wwan0
Test the interface:
sudo ping -c 5 dns.google -I wwan0
== Modem Reset ==
The modem module can be forced into hardware reset with the command:
sudo gpioset 0 22=1 ; sleep 0.3 ; sudo gpioset 0 22=0

= WiFi=
IOT-LINK optionally includes module with 802.11ax WiFi (6) and Bluetooth 5.3 BLE.
The [https://manpages.debian.org/stretch/network-manager/nmcli.1.en.html NetworkManager] can be used to manage WiFi interface.
== Enable/Disable WiFi Interface ==
* To enable WiFi interface:
sudo nmcli radio wifi on
* To disable WiFi interface:
sudo nmcli radio wifi off
== Network Scanning ==
* Sample WiFi scanning:
sudo nmcli dev wifi list ifname wlan0
The output will show the list of Access Points and Ad-Hoc cells in range.
== Connecting to Wireless Network ==
In the following example:
* Replace <SSID> and <PASSWORD> with the actual access point parameters:
sudo nmcli device wifi connect <SSID> password <PASSWORD> name WifiCon ifname wlan0
* Disconnect wireless network:
sudo nmcli connection down WifiCon
* Connect wireless network again:
sudo nmcli connection up WifiCon
== Creating Access Point ==
{{Note|Debian 12 ipv4 forwarding must be turned on manually}}
* Enable port forwarding to ethernet:
<pre>
internet_gateway=eth0
sudo iptables -t nat -A POSTROUTING -o $internet_gateway -j MASQUERADE
systemctl stop dnsmasq.service
sudo iptables -A FORWARD -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
sudo iptables -A FORWARD -i uap0 -o $internet_gateway -j ACCEPT
sudo iptables-save > /etc/iptables/iptables.rules
sudo sed -i 's/^#$net.ipv[4,6].*forward$/\1/' /etc/sysctl.conf
</pre>
In the following example:
* Replace <SSID> and <PASSWORD> with desired access point parameters:
sudo nmcli device wifi hotspot ssid <SSID> password <PASSWORD> con-name HotspotCon ifname uap0

* Disable wireless AP:
nmcli connection down HotspotCon
* Enable wireless AP again:
nmcli connection up HotspotCon

=Ethernet=
*IOT-LINK optionally features one Gigabit Ethernet port implemented with RTL8211FDI PHY
*One can manage an ethernet interface via [https://manpages.debian.org/stretch/network-manager/nmcli.1.en.html NetworkManager] or `ip`:
ip help

===Bandwidth test example===
Start iperf3 server on host:
iperf3 -s -i 60

Straight (client sends, server receives) 1 min. test with report each 10 sec.
iperf3 -t 60 -i 10 -c <serverIP>

Reverse (server sends, client receives) test
iperf3 -t 60 -i 10 -R -c <serverIP>

= Industrial Interfaces =
IOT-LINK optionally has the following interfaces on the 10-pin industrial terminal block:
 
* up to two RS485 (half-duplex)
* up to two CAN 2.0B
* three digital inputs/outputs.

For additional details, please refer to [https://www.compulab.com/products/iot-gateways/iot-LINK-industrial-iot-gateway/#devres IOT-LINK reference guide].

== CAN bus ==
IOT-LINK features up-to two optional CAN-FD ports implemented with i.MX93 CAN controller.
{{Note|CAN bus ports are only present in gateways ordered with the “FACAN” or “FBCAN” ordering options. CAN ports are mutually exclusive with RS485 ports.}}
CAN signals are routed to industrial I/O connector. Please refer to [https://www.compulab.com/products/iot-gateways/iot-LINK-industrial-iot-gateway/#devres IOT-LINK reference guide] for Industrial I/O Connector pin-out. 
Use an interface depending on the [https://www.compulab.com/products/iot-gateways/iot-LINK-industrial-iot-gateway/#ordering Configuration Options] of your unit:
{| class="wikitable" style="text-align:left;"
|-
| '''config option'''
| '''Linux network interface'''
|-
|FACAN
|can0
|-
|FBCAN
|can1
|-
|}
=== Example for '''can0''' ===
==== interface configuration ====
* Enable the CAN interface with bit-rate 1 Mb/sec:
sudo ip link set can0 up type can bitrate 1000000

==== Send/Receive packets ====
Use ''cansend'' and ''candump'' utilities to send and receive packets via CAN interface.
* Dump received data frames and error frames:
candump any,0:0,#FFFFFFFF
* Send:
:* Standard frame:
cansend can0 111#1122334455667788
:* Extended frame:
cansend can0 11111111#1122334455667788
:* Generate 50 random extended frames with 50 msec interval between each:
cangen -g 50 -e -D r -v can0 -n 50
* Disable the interfaces:
ip link set can0 down

== RS485 ==
IOT-LINK features up-to two optional RS485 ports implemented with MAX13488 transceivers interfaced with i.MX93 UART ports.
{{Note| RS485 ports are only present in gateways ordered with the “FARS4” or “FBRS4” ordering options. RS485 ports are mutually exclusive with CAN bus ports.}}
RS485 signals are routed to the industrial I/O connector. Please refer to [https://www.compulab.com/products/iot-gateways/iot-LINK-industrial-iot-gateway/#devres IOT-LINK reference guide] for Industrial I/O Connector pin-out. 
=== Configuration and Access ===
*Set a tty variable depending on the [https://www.compulab.com/products/iot-gateways/iot-LINK-industrial-iot-gateway/#ordering Configuration Options] of your unit
{| class="wikitable" style="text-align:left;"
|-
| '''config option'''
| '''set Linux tty interface'''
|-
|FARS4
|RS485_A=/dev/ttyLP6
|-
|FBRS4
|RS485_B=/dev/ttyLP4
|-
|}
* Access the RS485 interface can be accessed in Linux via the tty device in ''ttyRS485'' variable:
sudo stty -F ${RS485_B}

RS485 has an optional hardware-enabled termination. Please consult with the reference guide for enabling instructions.

=== Modbus RS485 ===
The following example demonstrates how to use RS485 in a Modbus RS485 Network where IOT-LINK performs as a Master device and queries XY-MD02 temperature and humidity sensor.
==== Software installation ====
Download and install ''modpoll'' - a command line based Modbus master simulator and test utility.
<pre>
wget https://www.modbusdriver.com/downloads/modpoll.tgz -P /tmp/
sudo tar -xvf /tmp/modpoll.tgz -C /opt/
</pre>
==== Device connection - example for port B ====
* Connect XY-MD02 sensor to appropriate Industrial I/O connector pins as below:
<pre>
------------------- --------------------
| *--(+)---< <------- 5V-30V | IOT-LINK |
| *--(-)---< <-------- GND | |
| XY-MD02 (RS485) | |------ Industrial |
| *--(A+)--< <--...--> >-(7)-*-| | I/O |
| *--(B-)--< <--...--> >-(8)-*-| | Connector |
------------------- --------------------
</pre>
==== Read data ====
* Read temperature once:
<pre>
sudo /opt/modpoll/arm-linux-gnueabihf/modpoll -b 9600 -p none -t 3 -c 1 -r 2 -1 ${RS485_B}
...
-- Polling slave...
[2]: 250
</pre>

* Poll temperature:
<pre>
sudo /opt/modpoll/arm-linux-gnueabihf/modpoll -b 9600 -p none -t 3 -c 1 -r 2 ${RS485_B}
...
-- Polling slave... (Ctrl-C to stop)
[2]: 254
-- Polling slave... (Ctrl-C to stop)
[2]: 254
-- Polling slave... (Ctrl-C to stop)
[2]: 254
...
</pre>

* Read humidity once:
<pre>
sudo /opt/modpoll/arm-linux-gnueabihf/modpoll -b 9600 -p none -t 3 -c 1 -r 3 -1 ${RS485_B}
...
-- Polling slave...
[3]: 515
</pre>

* Poll humidity:
<pre>
sudo /opt/modpoll/arm-linux-gnueabihf/modpoll -b 9600 -p none -t 3 -c 1 -r 3 ${RS485_B}
...
-- Polling slave... (Ctrl-C to stop)
[3]: 894
-- Polling slave... (Ctrl-C to stop)
[3]: 895
-- Polling slave... (Ctrl-C to stop)
[3]: 896
...
</pre>

* Read temperature & humidity once:
<pre>
sudo /opt/modpoll/arm-linux-gnueabihf/modpoll -b 9600 -p none -t 3 -c 2 -r 2 -1 ${RS485_B}
...
-- Polling slave...
[2]: 263
[3]: 606
</pre>

* Poll temperature & humidity:
<pre>
sudo /opt/modpoll/arm-linux-gnueabihf/modpoll -b 9600 -p none -t 3 -c 2 -r 2 ${RS485_B}
...
-- Polling slave... (Ctrl-C to stop)
[2]: 263
[3]: 545
-- Polling slave... (Ctrl-C to stop)
[2]: 263
[3]: 543
-- Polling slave... (Ctrl-C to stop)
[2]: 263
[3]: 542
...
</pre>

* Read slave address, baudrate, temperature & humidity corrections:
<pre>
sudo /opt/modpoll/arm-linux-gnueabihf/modpoll -b 9600 -p none -t 4 -c 4 -r 258 -1 ${RS485_B}
...
-- Polling slave...
[258]: 1
[259]: 9600
[260]: 0
[261]: 0
</pre>

== Digital I/O ==
IOT-LINK provides three signals which can be used as either digital inputs or outputs. 
Please refer to [https://www.compulab.com/products/iot-gateways/iot-LINK-industrial-iot-gateway/#devres IOT-LINK reference guide] for Industrial I/O Connector pin-out.
{{Note| External voltage supply in the range 6-24VDC must be supplied via DIO_VIN pin for correct operation of digital outputs.}}
=== Access ===
{| class="wikitable" style="text-align:left;"
|-
| align="center" | '''pin # on terminal block'''
| align="center" | '''Command to drive pin high'''
| align="center" | '''Command to read pin'''
|-
| align="center" |2
| align="" |<code>sudo gpioset 0 4=1</code>
| align="" |<code>sudo gpioget 0 4 > /dev/null; sudo gpioget 0 16</code>
|-
| align="center" |3
| align="" |<code>sudo gpioset 0 5=1</code>
| align="" |<code>sudo gpioget 0 5 > /dev/null; sudo gpioget 0 17</code>
|-
| align="center" |4
| align="" |<code>sudo gpioset 0 12=1</code>
| align="" |<code>sudo gpioget 0 12 > /dev/null; sudo gpioget 0 21</code>
|-
|}
{{Note| Read logical value is opposite to voltage level, i.e. if positive voltage is applied on a pin, its read value will be 0 and vice versa}}





= LEDs =
*IOT-LINK features:
:*user bi color LED: green and red.
:*bi color LED: amber and "power-blue" which is used by default to indicate system state

*LEDs are controlled via GPIO pins and can be accessed via [https://www.kernel.org/doc/Documentation/ABI/testing/sysfs-class-led sysfs] interface.
==Example==
*Choose a LED:
:<pre> LED=green</pre>
* Turn ON
:<pre> echo "1" | sudo tee -a /sys/class/leds/${LED}/brightness</pre>
* Turn OFF
:<pre> echo "0" | sudo tee -a /sys/class/leds/${LED}/brightness</pre>
* Set trigger
:<pre> echo "heartbeat" | sudo tee -a /sys/class/leds/${LED}/trigger</pre>

= TPM =
IOT-LINK is assembled with TPM 2.0 implemented with Infineon SLB9673. 

== TPM Basic Functionality ==
* Install the '''tpm2-tools''' package:
sudo apt-get update && sudo apt-get install tpm2-tools
* Validate basic functionality
sudo tpm2_getrandom --hex 32
The correct result will be returned generated 32-symbol key.

= RTC =
IOT-LINK features two real time clock (RTC) devices:
* AM1805 (default '''rtc0''') - for low current, battery backed time keeping whenever the main power supply is not present.
* i.MX93 internal RTC ('''rtc1''') - can be used as wake-up source for [[IOT-LINK: Debian: How-To#Low_Power_Modes | low power modes]]

== Access ==
* To read time and date run:
sudo hwclock

* To set the date run:
<pre>
sudo systemctl stop systemd-timesyncd
sudo systemctl disable systemd-timesyncd
sudo timedatectl set-local-rtc yes # do not write system time to the RTC
sudo hwclock --set --date="2020-01-01 12:00:00"
</pre>

= Watchdog =
By default watchdog is not configured.
systemctl show | grep RuntimeWatchdog
:<pre>RuntimeWatchdogUSec=0</pre>
The value '''RuntimeWatchdogUSec=0''' means that no watchdog device is opened, configured, or pinged
== Watchdog configuration ==
* Edit ''/etc/systemd/system.conf'' file to configure watchdog related parameters, in particular '''RuntimeWatchdogSec''' and '''ShutdownWatchdogSec'''.
the `'''#'''` comment sign should be removed from the relevant line in the file.
:'''RuntimeWatchdogSec''' - specifies the watchdog timeout for runtime services that are actively running during normal system operation. The value is in seconds and should be set to a positive integer. 
:'''ShutdownWatchdogSec''' - specifies the watchdog timeout for the shutdown process, insuring the system doesn't hang indefinitely during shutdown. The value is in seconds and should be set to a positive integer. 
* run:
systemctl daemon-reexec
* Verify watchdog configuration. e.g. if you have set <code>RuntimeWatchdogSec=10</code>:
:<pre> systemctl show | grep RuntimeWatchdog</pre>
:<pre>RuntimeWatchdogUSec=10s</pre>

== Watchdog testing ==
* Run the following command to simulate kernel panic:
echo "c" | sudo tee -a /proc/sysrq-trigger
* As a result, the watchdog is not fed and the system reboots after the value of RuntimeWatchdogSec

= Low Power Modes =
IOT-LINK supports the following low-power modes:
* Sleep mode - RAM content is preserved, and the system will quickly wake up into the operating system.
* Power-off mode - The system will restart into a clean boot.
Wake-up source:

* Timer alarm set in internal RTC (rtc1)
{{Important|Only the internal RTC (rtc1) can be used for the wake-up alarm. Main DC power must be present to preserve alarm settings.}}
==== Low power mode examples====

* Sleep mode with exit by RTC wake-up call:

sudo rtcwake --device /dev/rtc1 -s 5 -m mem
* Power-off mode with boot on RTC wake-up call:
sudo rtcwake --device /dev/rtc1 -s 60 -m off # system reboots after 60 seconds.

=CPU temperature=
*i.MX93 SoC features an internal temperature sensor.
*To read the current CPU temperature, run:
cat /sys/class/thermal/thermal_zone0/temp

[[Category:Linux]]
[[Category:IOT-LINK]]

@@ Line 122: / Line 122: @@
 *To set up IOT-LINK for cellular functionality,  install an active SIM card into SIM socket located behind the back panel. Please refer to [https://www.compulab.com/products/iot-gateways/iot-link-industrial-iot-gateway/#devres IOT-LINK reference guide] for details.<br>
 *Cellular antenna should be connected to SMA connector '''A''' on the front panel.
 == Cellular Connection ==
-. Configure APN (replace with your provider’s APN):
+=== SIMCOM SIM7672: LTE cat 1 bis ===
-  echo 'AT+CGDCONT=1,"IP","APN-NAME"' | socat - /dev/ttyACM2,crnl
+Configure APN
+ minicom -D /dev/ttyACM2
-. Request an IP:
+replace APN with your provider’s actual APN
   sudo dhclient wwan0
 If DNS resolution fails, ensure `/etc/resolv.conf` contains valid nameservers:
   nameserver 8.8.8.8
   nameserver 8.8.4.4
 == Modem Reset ==
 The modem module can be forced into hardware reset with the command:
   sudo gpioset 0 22=1 ; sleep 0.3 ; sudo gpioset 0 22=0
 = WiFi=

@@ Line 376: / Line 376: @@
 {{Note| External voltage supply in the range 6-24VDC must be supplied via DIO_VIN pin for correct operation of digital outputs.}}
 === Access ===
 {| class="wikitable" style="text-align:left;"
 |-
 | align="center" | '''pin # on terminal block'''
-| align="center" | '''Command to drive pin high'''
+| align="center" | '''Drive pin high'''
-| align="center" | '''Command to read pin'''
+| align="center" | '''Read pin'''
 |-
 | align="center" |2
-| align="" |<code>sudo gpioset 0 4=1</code>
+| align="" |<code>$DIOSET 4=1</code>
-| align="" |<code>sudo gpioget 0 4 > /dev/null; sudo gpioget 0 16</code>
+| align="" |<code>$DIOSET 4=0; $DIOGET 16</code>
 |-
 | align="center" |3
-| align="" |<code>sudo gpioset 0 5=1</code>
+| align="" |<code>$DIOSET 5=1</code>
-| align="" |<code>sudo gpioget 0 5 > /dev/null; sudo gpioget 0 17</code>
+| align="" |<code>$DIOSET 5=0; $DIOGET 17</code>
 |-
 | align="center" |4
-| align="" |<code>sudo gpioset 0 12=1</code>
+| align="" |<code>$DIOSET 12=1</code>
-| align="" |<code>sudo gpioget 0 12 > /dev/null; sudo gpioget 0 21</code>
+| align="" |<code>$DIOSET 12=0; $DIOGET 21</code>
 |-
 |}

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