View source for IOT-DIN-IMX8PLUS: Yocto Linux: How-To Guide

= Overview =
The example run-time Yocto Linux image for the CompuLab IOT-DIN-IMX8PLUS was generated with Kirkstone Yocto build.
The image includes the needed drivers and utilities to operate the hardware components of the IOT-DIN-IMX8PLUS.

The default Kirkstone Yocto image includes many software packages. Among them:

* Core system
* SSH server and client
* ConnMan
* ModemManager
* Bluez5 Bluetooth tools and daemons
* SocketCAN
* Minicom

= Serial Console =
IOT-DIN-IMX8PLUS provides a serial console on the front panel micro-USB '''DBG''' connector.</br>
== 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 CP2104 driver onto the host PC 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 (where n is a positive integer): /dev/ttyUSB0, /dev/ttyUSB1 ... /dev/ttyUSBn
#* In Windows PCs, the serial port usually will be denoted as one of the following (where n is a positive integer): COM1, COM2 ... COMn
# 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 terminal emulation program select the port identified in previous step and set the following serial port parameters:
<blockquote>
{{:SB-SOM: serial port parameters table}}
</blockquote>

= Connection and Login =
This Yocto rootfs comes with an empty root password.
No password is required for login.

To login into the Linux system, you may use a terminal emulator as described [[IOT-DIN-IMX8PLUS: Yocto Linux: How-To Guide#Serial Console | here]], or connect through the network (ssh).
{{Important|The following examples assume '''root''' user.}}

= Connectivity =
IOT-DIN-IMX8PLUS Yocto Linux Image includes [https://wiki.archlinux.org/title/ConnMan ConnMan] is a command-line network manager designed for use with embedded devices and fast resolve times. It can be used for managing all type of network interfaces:
# Wired
# Wireless
# Cellular

* Start '''ConnMan''' service prior to accessing network interfaces
<pre>root@iot-gate-imx8plus:~# systemctl start connman</pre>

* Display supported technologies
<pre>
root@iot-gate-imx8plus:~# connmanctl technologies
/net/connman/technology/cellular
  Name = Cellular
  Type = cellular
  Powered = True
  Connected = True
  Tethering = False
  TetheringFreq = 2412
/net/connman/technology/ethernet
  Name = Wired
  Type = ethernet
  Powered = False
  Connected = False
  Tethering = False
  TetheringFreq = 2412
/net/connman/technology/wifi
  Name = WiFi
  Type = wifi
  Powered = True
  Connected = False
  Tethering = False
  TetheringFreq = 2412
/net/connman/technology/bluetooth
  Name = Bluetooth
  Type = bluetooth
  Powered = False
  Connected = False
  Tethering = False
  TetheringFreq = 0
</pre>

== Ethernet ==
=== Enable/Disable Ethernet Interfaces ===
* To enable Ethernet interfaces:
:<pre>root@iot-gate-imx8plus:~# connmanctl enable ethernet</pre>
* To disable Ethernet interfaces:
:<pre>root@iot-gate-imx8plus:~# connmanctl disable ethernet</pre>

=== Enable/Disable Ethernet Connections ===
* To display Ethernet Connections:
:<pre>root@iot-gate-imx8plus:~# connmanctl services | grep ethernet</pre>
:Example (both Ethernet ports are connected to a LAN):
:<pre>root@iot-gate-imx8plus:~# connmanctl services | grep ethernet</pre>
:<pre>*AR Wired                ethernet_0001c030d7c3_cable</pre>
:<pre>*AR Wired                ethernet_0001c031ffe2_cable</pre>

* To enable Ethernet interfaces:
:<pre>root@iot-gate-imx8plus:~# connmanctl connect <ethernet service name></pre>
* To disable Ethernet interfaces:
:<pre>root@iot-gate-imx8plus:~# connmanctl disconnect <ethernet service name></pre>
:Example:
:<pre>root@iot-gate-imx8plus:~# connmanctl disconnect ethernet_0001c031ffe2_cable</pre>
:<pre>Disconnected ethernet_0001c031ffe2_cable</pre>
:<pre>root@iot-gate-imx8plus:~# connmanctl services | grep ethernet</pre>
:<pre>*AR Wired                ethernet_0001c030d7c3_cable</pre>
:<pre>*A  Wired                ethernet_0001c031ffe2_cable</pre>
:<pre>root@iot-gate-imx8plus:~# connmanctl connect ethernet_0001c031ffe2_cable</pre>
:<pre>Connected ethernet_0001c031ffe2_cable</pre>

== Cellular Modem ==
=== Wvdial ===
{{Note| Recommended method}}
[https://wiki.debian.org/Wvdial WvDial] is a Point-to-Point Protocol dialer that automatically detects modem, and can log into almost any Internet Service Provider without a complicated configuration.

==== Loading kernel modules ====
Load Point-to-Point protocol (PPP) driver modules prior to dialing:
<pre>
root@cl-som-imx7-sid:~# modprobe ppp_generic
root@cl-som-imx7-sid:~# modprobe ppp_async
root@cl-som-imx7-sid:~# modprobe ppp_synctty
root@cl-som-imx7-sid:~# modprobe bsd_comp
root@cl-som-imx7-sid:~# modprobe ppp_deflate
</pre>

==== Dialing ====
* Example configuration file {{filename|/etc/wvdial.conf}}:
<pre>
cat << eof > /etc/wvdial.conf
[Dialer cellular]
Init1 = ATZ
Init2 = ATQ0 V1 E1 S0=0 &C1 &D2 +FCLASS=0
Modem Type = Analog Modem
ISDN = 0
Phone = *99#
Modem = /dev/ttyUSB3
Username = dummy
Password = dummy
Baud = 9600
eof
</pre>
* Connect cellular network
:<pre>wvdial cellular &</pre>
* Verify the connection by pinging to google:
:<pre>sudo ping -c 5 dns.google</pre>
* Expected result:
:<pre>5 packets transmitted, 5 received, 0% packet loss, time 10ms</pre>
* Disconnect cellular network
:<pre>killall wvdial</pre>

=== ConnMan ===
==== Enable/Disable Cellular Interface ====
* To enable Ethernet interfaces:
:<pre>root@iot-gate-imx8plus:~# connmanctl enable cellular</pre>
* To disable Ethernet interfaces:
:<pre>root@iot-gate-imx8plus:~# connmanctl disable cellular</pre>

==== Enable/Disable Cellular Connections ====
* To display Cellular Connections:
:<pre>root@iot-gate-imx8plus:~# connmanctl services | grep cellular</pre>
:Example:
:<pre>root@iot-gate-imx8plus:~# connmanctl services | grep cellular</pre>
:<pre>*AR 425007               cellular_425071043611161_context1</pre>

* To connect Cellular network:
:<pre>root@iot-gate-imx8plus:~# connmanctl connect <cellular service name></pre>
* To disconnect Cellular network:
:<pre>root@iot-gate-imx8plus:~# connmanctl disconnect <cellular service name></pre>

== WiFi ==
=== Enable/Disable WiFi Interface ===
* To enable WiFi interface:
:<pre>root@iot-gate-imx8plus:~# connmanctl enable wifi</pre>
* To disable WiFi interface:
:<pre>root@iot-gate-imx8plus:~# connmanctl disable wifi</pre>

=== Network Scanning ===
* Sample WiFi scanning:
:<pre>root@iot-gate-imx8plus:~# connmanctl scan wifi</pre>
* Display list of Access Points and Ad-Hoc cells in range
:<pre>root@iot-gate-imx8plus:~# connmanctl services | grep wifi</pre>
:Example:
:<pre>   Compulab-Guest       wifi_8c1d96f18740_436f6d70756c61622d4775657374_managed_psk</pre>
:<pre>   ...</pre>
:<pre>   AP-Free              wifi_8c1d96f18740_6b77696b2d6d6f62_managed_none</pre>
:Where a service name pattern is as shown below: 
:<pre>wifi_<hashlocal>_<hashremote>_managed_<encrption></pre>

=== Connecting to Open Access Point ===
In the following example replace ''<hashlocal>'' and ''<hashremote>'' with the actual service parameters.
* Connect wireless network:
:<pre>root@iot-gate-imx8plus:~# connmanctl connect wifi_<hashlocal>_<hashremote>_managed_none</pre>
* Disconnect wireless network:
:<pre>root@iot-gate-imx8plus:~# connmanctl disconnect wifi_<hashlocal>_<hashremote>_managed_none</pre>

=== Connecting to Protected Access Point ===
For protected access points some information (like password) has to be provided to the ConnMan daemon.

The commands in this section show how to run '''connmanctl''' in interactive mode, it is required for running the agent command. 
* Start interactive mode:
:<pre>root@iot-gate-imx8plus:~# connmanctl</pre>
* Sample WiFi scanning (wait for scan completed):
:<pre>connmanctl> scan wifi</pre>
* Display a list of services:
:<pre>connmanctl> services</pre>
:<pre>   Compulab-Guest       wifi_8c1d96f18740_436f6d70756c61622d4775657374_managed_psk</pre>
:<pre>   ...</pre>
:<pre>   AP-Free              wifi_8c1d96f18740_6b77696b2d6d6f62_managed_none</pre>
* Register the agent to handle user requests:
:<pre>connmanctl> agent on</pre>
* Connect to one of the protected services. Replace ''<hashlocal>'' and ''<hashremote>'' with the actual service parameters: 
:<pre>connmanctl> connect wifi_<hashlocal>_<hashremote>_managed_psk</pre>
:<pre>Agent RequestInput wifi_<hashlocal>_<hashremote>_managed_psk</pre>
:<pre>  Passphrase = [ Type=psk, Requirement=mandatory ]</pre>
:<pre>Passphrase? </pre>
: Provide any information required by the daemon to complete the connection. The information requested may vary depending on the type of network.
* Quit:
:<pre>connmanctl> quit</pre>
* Disconnect wireless network:
:<pre>root@iot-gate-imx8plus:~# connmanctl disconnect wifi_<hashlocal>_<hashremote>_managed_psk</pre>
* Connect wireless network again:
:<pre>root@iot-gate-imx8plus:~# connmanctl connect wifi_<hashlocal>_<hashremote>_managed_psk</pre>

= GPS =
IOT-DIN-IMX8PLUS features an optional GPS interface implemented with the cellular modem module.</br>
== GPS antenna ==
A GPS antenna is required for GPS operation. GPS antenna is not included with IOT-DIN-IMX8PLUS. Any active GPS antenna with a male SMA connector can be used with IOT-DIN-IMX8PLUS.</br>
GPS antenna should be attached to the '''AUX''' SMA connector on the gateway.<br>
{{Note|GPS antenna should be positioned at least 1m away from the gateway}}

== Using GPS ==
The [https://manpages.debian.org/jessie/gpsd-clients/cgps.1.en.html cgps] client can be used to display the GPS information. <br>
The [https://manpages.debian.org/testing/modemmanager/mmcli.8 ModemManager] can be used to check the modem status.
For example, the following command shows the presence of the modem and the ID of its interfaces.
<pre>
root@iot-gate-imx8plus:~# mmcli -m 0
</pre>

The cgps client utility depends on the gpsd daemon (starts automatically after the initialization command is performed).
* Initialization of the GPS interface:
<pre>
root@iot-gate-imx8plus:~# sed -i "/^DEVICES=.*/c\DEVICES=\"/dev/ttyUSB1\"" /etc/default/gpsd
</pre>

* Enable the GPS with the following AT commands:
<pre>
root@iot-gate-imx8plus:~# echo AT+QGPS= 1 | socat - /dev/ttyUSB2,crnl
</pre>
* A full power cycle is required before using GPS. Shut down the gateway, remove the main DC power for at least 20 sec, and restart.
* Start the cgps client to display GPS information.

The synchronization process might take a few minutes. 

<pre>
root@iot-gate-imx8plus:~# cgps
┌───────────────────────────────────────────┐┌─────────────────────────────────┐
│    Time:       2022-05-04T14:13:30.000Z   ││PRN:   Elev:  Azim:  SNR:  Used: │
│    Latitude:    32.65985123 N             ││  71    29    123    22      Y   │
│    Longitude:   35.10027205 E             ││  85    27    047    22      Y   │
│    Altitude:   102.700 m                  ││                                 │
│    Speed:      0.00 kph                   ││                                 │
│    Heading:    128.7 deg (true)           ││                                 │
│    Climb:      6.00 m/min                 ││                                 │
│    Status:     3D FIX (53 secs)           ││                                 │
│    Longitude Err:   n/a                   ││                                 │
│    Latitude Err:    n/a                   ││                                 │
│    Altitude Err:    +/- 18 m              ││                                 │
│    Course Err:      n/a                   ││                                 │
│    Speed Err:       n/a                   ││                                 │
│    Time offset:     -3.682                ││                                 │
│    Grid Square:     KM72np                ││                                 │
└───────────────────────────────────────────┘└─────────────────────────────────┘
</pre>

* Disable the GPS with the following AT commands:
<pre>
root@iot-gate-imx8plus:~# echo AT+QGPSEND | socat - /dev/ttyUSB2,crnl
</pre>


= Industrial Interfaces =
IOT-DIN-IMX8PLUS implements following industrial interfaces on the 16-pin industrial terminal block:
<br>
1x RS232 (2-wire); 1x RS485 (half-duplex); 1x CAN 2.0B; 2x digital inputs; 2x digital outputs.

Please refer to Industrial I/O Connector pin-out for more details.

== CAN ==
IOT-DIN-IMX8PLUS features one CAN 2.0B port implemented with i.MX8M Plus CAN controller.<br>
CAN bus signals are routed to industrial I/O connector.

=== CAN interface configuration ===
* Configure the CAN interface bit-rate to 1 Mbits/sec:
<pre>
root@iot-gate-imx8plus:~# ip link set can0 type can bitrate 1000000
</pre>
* Enable the CAN interface:
<pre>
root@iot-gate-imx8plus:~# ip link set can0 up
</pre>

=== Send/Receive packets ===
Use ''cansend'' and ''candump'' utilities to send and receive packets via CAN interface. 
* Send standard CAN frame (on the first device):
<pre>
root@iot-gate-imx8plus:~# cansend can0 111#1122334455667788
</pre>

* Send extended CAN frame (on the first device):
<pre>
root@iot-gate-imx8plus:~# cansend can0 11111111#1122334455667788
</pre>

* CAN frames (extended mode) generator, random payload, interval between two successive flames 50 msec:
<pre>
root@iot-gate-imx8plus:~# cangen -g 50 -e -D r -v can0
...
...
</pre>

* Dump all received data frames as well as error frames:
<pre>
root@iot-gate-imx8plus:~# candump any,0:0,#FFFFFFFF
...
...
</pre>

== RS232 ==
RS232 function is implemented with MAX3221 (or compatible) transceiver interfaced with i.MX8M Plus UART port.


=== Configuration and Access ===
RS232 interface can be accessed in Linux via '''ttyRS232''' tty device.

== RS485 ==
RS485 function is implemented with MAX13488 (or compatible) transceiver interfaced with i.MX8M Plus UART port.

=== Configuration and Access ===
RS485 interface can be accessed in Linux via '''ttyRS485''' tty device.

=== Modbus RS485 ===
The following example demonstrates how to use RS485 module installed into industrial I/O slot A in a Modbus RS485 Network.
IOTG-IMX8PLUS 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>
root@iot-gate-imx8plus:~# wget https://www.modbusdriver.com/downloads/modpoll.tgz -P /tmp/
...
root@iot-gate-imx8plus:~# tar -xvf /tmp/modpoll.tgz -C /opt/
...
</pre>

==== Device connection ====
* Connect XY-MD02 sensor to appropriate Industrial I/O connector pins as below:
:* '''A+''': XY-MD02 A+ to IOT-GATE-iMX8PLUS / SBC-IOT-IMX8PLUS P8-01
:* '''B-''': XY-MD02 B- to IOT-GATE-iMX8PLUS / SBC-IOT-IMX8PLUS P8-03
<pre>
--------------------                                  -------------------------
|                  |                                  |                       |
|                  *--(+)---< <------------- 5V-30V   |     IOTG-IMX8PLUS     |
|                  |                                  |   (SBC-IOT-IMX8PLUS)  |
|                  *--(-)---< <-------------- GND     |------  ------------   |
| XY-MD02 (RS485)  |                                  |     |==| IE-RS485 |   |
|                  *--(A+)--< <---...---> >---(1)---*-|     |  ------------   |
|                  |                                  | P8  |     Slot A      |
|                  *--(B-)--< <---...---> >---(3)---*-|     |                 |
|                  |                                  |------                 |
--------------------                                  ------------------------- 
</pre>

==== Read data ====

* Read temperature once:
<pre>
root@iot-gate-imx8plus:~# /opt/modpoll/arm-linux-gnueabihf/modpoll -b 9600 -p none -t 3 -c 1 -r 2 -1 /dev/ttyRS485_A
modpoll 3.10 - FieldTalk(tm) Modbus(R) Master Simulator
Copyright (c) 2002-2021 proconX Pty Ltd
Visit https://www.modbusdriver.com for Modbus libraries and tools.

Protocol configuration: Modbus RTU, FC4
Slave configuration...: address = 1, start reference = 2, count = 1
Communication.........: /dev/ttyRS485_A, 9600, 8, 1, none, t/o 1.00 s, poll rate 1000 ms
Data type.............: 16-bit register, input register table

-- Polling slave...
[2]: 250
</pre>

* Poll temperature:
<pre>
root@iot-gate-imx8plus:~# /opt/modpoll/arm-linux-gnueabihf/modpoll -b 9600 -p none -t 3 -c 1 -r 2 /dev/ttyRS485_A
modpoll 3.10 - FieldTalk(tm) Modbus(R) Master Simulator
Copyright (c) 2002-2021 proconX Pty Ltd
Visit https://www.modbusdriver.com for Modbus libraries and tools.

Protocol configuration: Modbus RTU, FC4
Slave configuration...: address = 1, start reference = 2, count = 1
Communication.........: /dev/ttyRS485_A, 9600, 8, 1, none, t/o 1.00 s, poll rate 1000 ms
Data type.............: 16-bit register, input register table

-- 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>
root@iot-gate-imx8plus:~# /opt/modpoll/arm-linux-gnueabihf/modpoll -b 9600 -p none -t 3 -c 1 -r 3 -1 /dev/ttyRS485_A
modpoll 3.10 - FieldTalk(tm) Modbus(R) Master Simulator
Copyright (c) 2002-2021 proconX Pty Ltd
Visit https://www.modbusdriver.com for Modbus libraries and tools.

Protocol configuration: Modbus RTU, FC4
Slave configuration...: address = 1, start reference = 3, count = 1
Communication.........: /dev/ttyRS485_A, 9600, 8, 1, none, t/o 1.00 s, poll rate 1000 ms
Data type.............: 16-bit register, input register table

-- Polling slave...
[3]: 515
</pre>

* Poll humidity:
<pre>
root@iot-gate-imx8plus:~# /opt/modpoll/arm-linux-gnueabihf/modpoll -b 9600 -p none -t 3 -c 1 -r 3 /dev/ttyRS485_A
modpoll 3.10 - FieldTalk(tm) Modbus(R) Master Simulator
Copyright (c) 2002-2021 proconX Pty Ltd
Visit https://www.modbusdriver.com for Modbus libraries and tools.

Protocol configuration: Modbus RTU, FC4
Slave configuration...: address = 1, start reference = 3, count = 1
Communication.........: /dev/ttyRS485_A, 9600, 8, 1, none, t/o 1.00 s, poll rate 1000 ms
Data type.............: 16-bit register, input register table

-- 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>
root@iot-gate-imx8plus:~# /opt/modpoll/arm-linux-gnueabihf/modpoll -b 9600 -p none -t 3 -c 2 -r 2 -1 /dev/ttyRS485_A
modpoll 3.10 - FieldTalk(tm) Modbus(R) Master Simulator
Copyright (c) 2002-2021 proconX Pty Ltd
Visit https://www.modbusdriver.com for Modbus libraries and tools.

Protocol configuration: Modbus RTU, FC4
Slave configuration...: address = 1, start reference = 2, count = 2
Communication.........: /dev/ttyRS485_A, 9600, 8, 1, none, t/o 1.00 s, poll rate 1000 ms
Data type.............: 16-bit register, input register table

-- Polling slave...
[2]: 263
[3]: 606
</pre>

* Poll temperature & humidity:
<pre>
root@iot-gate-imx8plus:~# /opt/modpoll/arm-linux-gnueabihf/modpoll -b 9600 -p none -t 3 -c 2 -r 2 /dev/ttyRS485_A
modpoll 3.10 - FieldTalk(tm) Modbus(R) Master Simulator
Copyright (c) 2002-2021 proconX Pty Ltd
Visit https://www.modbusdriver.com for Modbus libraries and tools.

Protocol configuration: Modbus RTU, FC4
Slave configuration...: address = 1, start reference = 2, count = 2
Communication.........: /dev/ttyRS485_A, 9600, 8, 1, none, t/o 1.00 s, poll rate 1000 ms
Data type.............: 16-bit register, input register table

-- 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>
root@iot-gate-imx8plus:~# /opt/modpoll/arm-linux-gnueabihf/modpoll -b 9600 -p none -t 4 -c 4 -r 258 -1 /dev/ttyRS485_A
modpoll 3.10 - FieldTalk(tm) Modbus(R) Master Simulator
Copyright (c) 2002-2021 proconX Pty Ltd
Visit https://www.modbusdriver.com for Modbus libraries and tools.

Protocol configuration: Modbus RTU, FC3
Slave configuration...: address = 1, start reference = 258, count = 4
Communication.........: /dev/ttyRS485_A, 9600, 8, 1, none, t/o 1.00 s, poll rate 1000 ms
Data type.............: 16-bit register, output (holding) register table

-- Polling slave...
[258]: 1
[259]: 9600
[260]: 0
[261]: 0
</pre>

== Digital I/O  ==
Digital I/O module features 4 digital inputs and 4 digital outputs and can be installed into slot D.
Four digital inputs are implemented with the CLT3-4B digital termination following EN 61131-2. 
Four digital outputs are implemented with the VNI4140K solid-state relay following EN 61131-2.<br>
{{Note|Digital I/O module requires an external voltage supply up to 24V to be properly connected. Please refer to Industrial I/O Connector pin-out for more details.}}

=== Configuration and Access ===
Use ''iotg-imx8plus-dio'' utility to access digital inputs and outputs.

The example below shows how to access Digital inputs and outputs.
* Drive OUT2 pin HI:
<pre>
root@iot-gate-imx8plus:~# iotg-imx8plus-dio -o 2 1
</pre>

* Read IN3 pin state (LO):
<pre>
root@iot-gate-imx8plus:~# iotg-imx8plus-dio -i 3
0
</pre>

= RTC =

IOT-DIN-IMX8PLUS RTC is implemented with the AM1805 real-time clock (RTC) chip.</br>
Back-up battery keeps the RTC running to maintain clock and time information whenever the main power supply is not present.

== Accessing and setting the RTC ==
* To access the RTC time and date run:
<pre>
compulab@iot-gate-imx8plus:~$ sudo hwclock
2022-08-04 12:38:10.577874+00:00
</pre>

* To set the date and write it into the RTC do the following: 
<pre>
compulab@iot-gate-imx8plus:~$ sudo date -s "31 Dec 2021 10:00:00"
Fri Dec 31 10:00:00 IST 2021
compulab@iot-gate-imx8plus:~$ sudo hwclock -w
compulab@iot-gate-imx8plus:~$ sudo hwclock 
2021-12-31 10:00:08.317403+02:00
</pre>

= Watchdog =

IOT-DIN-IMX8PLUS watchdog function is implemented with the i.MX8M Plus watchdog.</br>
By default, the watchdog is not configured.
:<pre>compulab@iot-gate-imx8plus:~$ systemctl show | grep RuntimeWatchdog</pre>
:<pre>RuntimeWatchdogUSec=0</pre>
The value '''RuntimeWatchdogUSec=0''' means watchdog logic is disabled: 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'''.
:'''RuntimeWatchdogSec''' - specifies the watchdog timeout for runtime services, meaning services that are actively running during normal system operation. The value is in seconds and should be set to a positive integer.<br>
:'''ShutdownWatchdogSec''' - specifies the watchdog timeout for the shutdown process, insuring the system doesn't hang indefinitely during the shutdown. The value is in seconds and should be set to a positive integer.<br>

* Reboot the device
* Verify watchdog configuration
:<pre>compulab@iot-gate-imx8plus:~$ systemctl show | grep RuntimeWatchdog</pre>
:<pre>RuntimeWatchdogUSec=10s</pre>

== Watchdog testing ==
* Run the following command to simulate kernel panic:
:<pre>compulab@iot-gate-imx8plus:~$ sudo su</pre>
:<pre>root@iot-gate-imx8plus:~# echo "c" > /proc/sysrq-trigger</pre>
* As a result, the watchdog is not fed and the system reboots after 10 sec.

= LEDs =
IOT-DIN-IMX8PLUS features two user Bi-Color (Red + Green) LEDs found on [[IOT-DIN-IMX8PLUS: Getting Started#Front panel|front panel]].<br>
LEDs are controlled via GPIO pins and can be accessed via [https://www.kernel.org/doc/Documentation/ABI/testing/sysfs-class-led sysfs] interface.

* LEDs are referred to as ''Green_1'', ''Red_1'', ''Green_2'' and ''Red_2''
* Choose a LED (LED2 Red in this example):
:<pre>root@iot-gate-imx8plus:~# LED=Red_2</pre>
* Turn the LED ON
:<pre>root@iot-gate-imx8plus:~# echo "1" | tee -a /sys/class/leds/${LED}/brightness</pre>
* Turn the LED OFF
:<pre>root@iot-gate-imx8plus:~# echo "0" | tee -a /sys/class/leds/${LED}/brightness</pre>
* Set LED's trigger
:<pre>root@iot-gate-imx8plus:~# echo "heartbeat" | tee -a /sys/class/leds/${LED}/trigger</pre>

= TPM =
IOT-DIN-IMX8PLUS features TPM 2.0 implemented with Infineon SLB9670.<br>
:<pre>compulab@iot-gate-imx8plus:~$ modprobe tpm_tis_spi</pre>
* Make sure that the tpm package is installed:
:<pre>compulab@iot-gate-imx8plus:~$ dpkg -l eltt2 &>/dev/null && echo "Installed" || echo "Not installed" </pre>
:If '''Installed''', then goto the next step.
* Validate basic functionality
:<pre>compulab@iot-gate-imx8plus:~$ eltt2 -t full && eltt2 -T</pre>

[[Category:Yocto]]
[[Category:IOT-DIN-IMX8PLUS]]