Difference between revisions of "IOT-GATE-IMX8PLUS and SBC-IOT-IMX8PLUS: Debian Linux: How-To Guide"
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=== Configuration and Access === | === Configuration and Access === | ||
Once properly installed on a specific I/O slot, RS485 interface can be accessed in Linux via '''ttyRS485_X''' tty device, where '''X''' is a slot name: A, B, C. | Once properly installed on a specific I/O slot, RS485 interface can be accessed in Linux via '''ttyRS485_X''' tty device, where '''X''' is a slot name: A, B, C. | ||
+ | |||
+ | RS485 has an optional software-enabled termination. Please note that the termination is disabled each time the device goes through power-cycle. <BR> | ||
+ | Linux commands to switch termination state: | ||
+ | {| class="wikitable" style="font-family:Arial, Helvetica, sans-serif !important;" | ||
+ | |- style="font-weight:bold;" | ||
+ | ! SLOT | ||
+ | ! Enable termination | ||
+ | ! Disable termination | ||
+ | |- | ||
+ | | A | ||
+ | | GPIOSET 5 12=0 | ||
+ | | GPIOSET 5 12=1 | ||
+ | |- | ||
+ | | B | ||
+ | | GPIOSET 5 13=0 | ||
+ | | GPIOSET 5 13=1 | ||
+ | |- | ||
+ | | C | ||
+ | | GPIOSET 5 14=0 | ||
+ | | GPIOSET 5 14=1 | ||
+ | |} | ||
=== Modbus RS485 === | === Modbus RS485 === |
Revision as of 15:51, 27 March 2023
Contents
Overview
The example run-time Linux filesystem image for the CompuLab IOT-GATE-IMX8PLUS Internet of Things Gateway and SBC-IOT-IMX8PLUS Internet of Things Single Board Computer is based on Debian GNU/Linux Bullseye. The default Debian buster Linux image includes more than 650 software packages. Among them:
- Core system
- Debian package management system
- SSH server and client
- PulseAudio configuration and usage utilities
- NetworkManager
- ModemManager
- Bluez5 Bluetooth tools and daemons
- Docker
Connection and Login
This Debian rootfs comes with a default sudo user compulab. User's assword has to be set at the very first login:
Debian GNU/Linux 11 iot-gate-imx8plus ttymxc1 iot-gate-imx8plus login: compulab You are required to change your password immediately (administrator enforced). New password: Retype new password:
To login into the Linux system, use a terminal emulator as described here, or connect through the network (ssh).
Package Management
The IOT-GATE-IMX8PLUS / SBC-IOT-IMX8PLUS Debian Linux image includes everything required to use the Debian package management utilities.
Use apt and 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 folowing command:
compulab@iot-gate-imx8plus:~$ cat /proc/device-tree/baseboard-sn
- To read the product configuration part number, issue the following command:
compulab@iot-gate-imx8plus:~$ cat /proc/device-tree/baseboard-options
Device Tree
Available Device Tree Files
IOT-GATE-iMX8PLUS Debian package includes the following dtb files:
<fdt_file_name> | Description | Remarks |
iot-gate-imx8plus.dtb | default hardware configuration | |
iot-gate-imx8plus-m2tpm.dtb | default hardware configuration + TPM add-on board | TPM add-on uses the M.2 expansion socket (P19). Cannot be combined with any other add-on board |
iot-gate-imx8plus-brkout_pwm_gpio.dtb | default hardware configuration + break-out add-on board (2x PWMs, 4x GPIOs) | Break-out add-on uses the M.2 expansion socket (P19). Cannot be combined with any other add-on board |
Set a device tree
IOT-GATE-iMX8PLUS Debian provides two methods to switch between dtb files:
- U-Boot environment
The U-boot fdtfile variable contains the device tree name that will be loaded into the RAM. This variable can be changed by:
Environment | Command |
U-Boot | setenv fdtfile <fdt_file_name>; saveenv;
|
Linux | fw_setenv fdtfile <fdt_file_name>
|
- GRUB environment
Environment | Command/Procedure |
GRUB Boot Menu | Goto "Advanced Boot Options" and choose a device tree from the provided dtb list. |
Linux | grub-editenv /boot/EFI/BOOT/grubenv set fdt_file=<fdt_file_name>
|
Docker
The 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.
compulab@iot-gate-imx8plus:~$ sudo docker run -it ubuntu ... 0;root@b053b4b3817d: /root@b053b4b3817d:/# cat /etc/issue Ubuntu 22.04.1 LTS \n \l ...
Cellular Modem
IOT-GATE-IMX8PLUS / SBC-IOT-IMX8PLUS cellular interface is implemented with a mini-PCIe cellular modem module and a
nano-SIM socket. To set up IOT-GATE-IMX8PLUS / SBC-IOT-IMX8PLUS for cellular functionality, install an active SIM card into
the front panel nano-SIM socket (U10).
Cellular module should be installed into mini-PCIe socket P3.
ModemManager
The ModemManager can be used to log into almost any Internet Service Provider with simple configuration setup.
In the following example:
- Replace ISP-APN with the APN name of the cellular provider.
compulab@iot-gate-imx8plus:~$ sudo nmcli connection add type gsm ifname '*' con-name CellularCon apn <ISP-APN>
- Connect cellular network
compulab@iot-gate-imx8plus:~$ sudo nmcli connection up CellularCon
- Disconnect cellular network
compulab@iot-gate-imx8plus:~$ sudo nmcli connection down CellularCon
GPS
IOT-GATE-IMX8PLUS features an optional GPS interface implemented with the cellular modem module.
GPS antenna
GPS antenna is required for GPS operation. GPS antenna is not included with IOT-GATE-IMX8PLUS. Any active GPS antenna with a male SMA connector can be used with IOT-GATE-IMX8PLUS.
GPS antenna should be attached to the AUX SMA connector on the gateway.
![]() |
GPS antenna should be positioned at least 1m away from the gateway |
Using GPS
The cgps client can be used to display the GPS information.
The 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.
root@iot-gate-imx8plus:~# mmcli -m 0
The cgps client utility depends on the gpsd daemon (starts automatically after the initialization command is performed).
- Initialization of the GPS interface:
root@iot-gate-imx8plus:~# sed -i "/^DEVICES=.*/c\DEVICES=\"/dev/ttyUSB1\"" /etc/default/gpsd
- Enable the GPS with the following AT commands:
root@iot-gate-imx8plus:~# echo AT+QGPS= 1 | socat - /dev/ttyUSB2,crnl
- Full power cycle is required before using GPS. Shut down the gateway, remove 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.
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 ││ │ └───────────────────────────────────────────┘└─────────────────────────────────┘
- Disable the GPS with the following AT commands:
root@iot-gate-imx8plus:~# echo AT+QGPS= 0 | socat - /dev/ttyUSB2,crnl
WiFi
IOT-GATE-IMX8PLUS / SBC-IOT-IMX8PLUS features an optional 802.11ax WiFi interface, implemented with the Intel WiFi 6 AX210 module.
The NetworkManager can be used to manage WiFi interface.
Enable/Disable WiFi Interface
- To enable WiFi interface:
compulab@iot-gate-imx8plus:~$ sudo nmcli radio wifi on
- To disable WiFi interface:
compulab@iot-gate-imx8plus:~$ sudo nmcli radio wifi off
Network Scanning
- Sample WiFi scanning:
compulab@iot-gate-imx8plus:~$ nmcli dev wifi list
- The output will show the list of Access Points and Ad-Hoc cells in range.
Connecting to Access Point
In the following example:
- Replace <SSID> and <PASSWORD> with the actual access point parameters:
compulab@iot-gate-imx8plus:~$ sudo nmcli device wifi connect <SSID> password <PASSWORD> name WifiCon
- Disconnect wireless network:
compulab@iot-gate-imx8plus:~$ sudo nmcli connection down WifiCon
- Connect wireless network again:
compulab@iot-gate-imx8plus:~$ sudo nmcli connection up WifiCon
Creating Access Point
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
- Disable wireless AP:
compulab@iot-gate-imx8plus:~$ sudo nmcli connection down HotspotCon
- Enable wireless AP again:
compulab@iot-gate-imx8plus:~$ sudo nmcli connection up HotspotCon
Controller–area network (CAN)
IOT-GATE-IMX8PLUS / SBC-IOT-IMX8PLUS features up to two CAN 2.0B ports implemented with i.MX8M Plus CAN controllers.
- canE: permanent: always enabled and accessible
- canC: optional: always enabled, but can be accessed only when CAN I/O module is installed
![]() |
IOT-GATE-IMX8PLUS / SBC-IOT-IMX8PLUS CAN signals are routed to industrial I/O connector (P8) |
The following example demonstrates how to configure and use the permanent CAN interface canE.
CAN interface configuration
- Configure the CAN interface bit-rate to 1 Mbits/sec:
compulab@iot-gate-imx8plus:~$ sudo ip link set canE type can bitrate 1000000
- Enable the CAN interface:
compulab@iot-gate-imx8plus:~$ sudo ip link set canE up
Send/Receive packets
Use cansend and candump utilities to send and receive packets via CAN interface.
- Send standard CAN frame (on the first device):
compulab@iot-gate-imx8plus:~$ sudo cansend canE 111#1122334455667788
- Send extended CAN frame (on the first device):
compulab@iot-gate-imx8plus:~$ sudo cansend canE 11111111#1122334455667788
- CAN frames (extended mode) generator, random payload, interval between two successive flames 50 msec:
compulab@iot-gate-imx8plus:~$ sudo cangen -g 50 -e -D r -v canE ... canE 1E5137F4#0F.4D.8B.7A.25.4D.DB.21 canE 1B6C965C#8C.DE.96.58.69.5F.D5.26 canE 1BD23086#8D.DB.C4.3E.81.57.BA.34 canE 127B2322#F4.16.31.2E.34.04.62 canE 1A6366DB#A8.73.C0.37.D8 canE 03620EE4# canE 023AC34D#C6.08.BD.2A.04.B3.BF.43 canE 1C19AD2E#09.C1.B3.26.23.E5.6A.5A canE 02BCA994#48.32.46.7C.F0.3F.29.1E canE 08104C67#59.9F.FE.44 canE 1C280582#6F.D4.9C.38.A5.28.A3 canE 0BC219EE#D9.2C.05 canE 04AA80B8#A1.93 canE 1A3E2392#AD.98 canE 0025950E#E3.99.38 ...
- Dump all received data frames as well as error frames:
compulab@iot-gate-imx8plus:~$ sudo candump any,0:0,#FFFFFFFF ... canE 0CC89C1A [1] 51 canE 0A097EFB [0] canE 02B59BD5 [5] 68 6F 47 64 D9 canE 03743A1E [7] FA BF E4 38 3E BF C8 canE 13C9B644 [8] 30 FB 60 6F E1 FC 55 65 canE 018A8975 [0] canE 0C9C8179 [0] canE 011F5D90 [6] 65 DB DD 5A AA F9 canE 07B7FD18 [6] CC 96 26 1D 13 7C canE 1FBD7177 [8] 69 BF 8D 1E 4C 0D 73 02 canE 107A7E2D [2] 25 D3 canE 12B9E279 [8] 89 77 B7 54 BD 98 83 06 canE 112A44EA [8] 9E 95 D9 6B 60 CE B4 52 canE 0ADF9869 [3] C8 A0 27 canE 1580C274 [5] B2 7A F7 43 04 canE 06DDDBCC [7] AF 19 88 04 E4 D8 95 canE 127FA5CE [8] F7 54 57 20 45 17 3D 12 canE 09A37893 [0] canE 01BA4332 [6] 0B AF 0C 2E AB 25 canE 180A8AD5 [5] 68 BE F7 5A C0 canE 06DC994E [7] 20 9E E9 7B B8 31 BC ...
Industrial Interfaces
IOT-GATE-IMX8PLUS / SBC-IOT-IMX8PLUS implements industrial interfaces with four I/O slots (IE) that can be fitted with up-to four different I/O modules. Slots are referred to as A, B, C and D.
Available I/O modules types:
- RS232 (2-wire)
- RS485 (half duplex)
- Digital I/O (4x DI + 4x DO)
- CAN 2.0B
![]() |
IOT-GATE-IMX8PLUS / SBC-IOT-IMX8PLUS industrial I/O signals are routed to Industrial I/O Connector (P8) |
Please refer to Industrial I/O Connector pin-out for more details.
So far industrial I/O modules do not require any special configuration.
RS232
RS232 function is implemented with MAX3221 (or compatible) transceiver interfaced with i.MX8M Plus UART ports.
RS232 modules can be installed into I/O slots A, B and C (configuration options FARS2, FBRS2, FCRS2). Up to three RS232 modules can be installed simultaneously.
Configuration and Access
Once properly installed on a specific I/O slot, RS232 interface can be accessed in Linux via ttyRS232_X tty device, where X is a slot name: A, B, C.
RS485
RS485 function is implemented with MAX13488 (or compatible) transceiver interfaced with i.MX8M Plus UART ports.
RS485 modules can be installed in I/O slots A, B and C (configuration options FARS4, FBRS4, FCRS4). Up to three RS485 modules can be installed simultaneously.
Configuration and Access
Once properly installed on a specific I/O slot, RS485 interface can be accessed in Linux via ttyRS485_X tty device, where X is a slot name: A, B, C.
RS485 has an optional software-enabled termination. Please note that the termination is disabled each time the device goes through power-cycle.
Linux commands to switch termination state:
SLOT | Enable termination | Disable termination |
---|---|---|
A | GPIOSET 5 12=0 | GPIOSET 5 12=1 |
B | GPIOSET 5 13=0 | GPIOSET 5 13=1 |
C | GPIOSET 5 14=0 | GPIOSET 5 14=1 |
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.
compulab@iot-gate-imx8plus:~$ wget https://www.modbusdriver.com/downloads/modpoll.tgz -P /tmp/ ... compulab@iot-gate-imx8plus:~$ sudo tar -xvf /tmp/modpoll.tgz -C /opt/ ...
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
-------------------- ------------------------- | | | | | *--(+)---< <------------- 5V-30V | IOTG-IMX8PLUS | | | | (SBC-IOT-IMX8PLUS) | | *--(-)---< <-------------- GND |------ ------------ | | XY-MD02 (RS485) | | |==| IE-RS485 | | | *--(A+)--< <---...---> >---(1)---*-| | ------------ | | | | P8 | Slot A | | *--(B-)--< <---...---> >---(3)---*-| | | | | |------ | -------------------- -------------------------
Read data
- Read temperature once:
compulab@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
- Poll temperature:
compulab@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 ...
- Read humidity once:
compulab@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
- Poll humidity:
compulab@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 ...
- Read temperature & humidity once:
compulab@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
- Poll temperature & humidity:
compulab@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 ...
- Read slave address, baudrate, temperature & humidity corrections:
compulab@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
Digital I/O
Digital I/O module features 4 digital inputs and 4 digital outputs and can be installed into slot D (configuration option FDIO).
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.
![]() |
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:
compulab@iot-gate-imx8plus:~$ sudo iotg-imx8plus-dio -o 2 1
- Read IN3 pin state (LO):
compulab@iot-gate-imx8plus:~$ sudo iotg-imx8plus-dio -i 3 0
CAN
CAN function is implemented with i.MX8M Plus Flexible Controller Area Network (FlexCAN) communication controller.
CAN module can be installed into I/O slot C (configuration option FCCAN).
Configuration and Access
Once properly installed, CAN I/O module can be accessed in Linux via canC network interface. Refer to the CAN section for configuration and usage example.
Add-on boards
IOT-GATE-IMX8PLUS / SBC-IOT-IMX8PLUS features expansion interface via M.2 Key-E socket P19. The expansion connector allows integration of custom add-on boards into IOT-GATE-IMX8PLUS / SBC-IOT-IMX8PLUS. The expansion connector features embedded interfaces such as I2C, SPI, PWM, GPIO, etc.
![]() |
Please refer to Expansion Connector pin-out for more details. |
Available add-on boards:
- TPM 2.0: implemented with Infineon SLB9670
- Break-out: exposes expansion connector signals on 100-mil headers
TPM
IOT-GATE-IMX8PLUS / SBC-IOT-IMX8PLUS can be optionally (configuration option FXTPM) assembled with a TPM 2.0 add-on board implemented with Infineon SLB9670.
- Install TPM add-on board into M.2 Socket (P19) if required
- Boot Linux kernel with iot-gate-imx8plus-m2tpm.dtb device tree
- Verify that the TPM device was created:
compulab@iot-gate-imx8plus:~$ ls -lh /dev/tpm*
- Otherwise load TPM kernel object:
compulab@iot-gate-imx8plus:~$ sudo modprobe tpm_tis_spi
- Install the tpm2-tools package:
compulab@iot-gate-imx8plus:~$ sudo apt-get update && apt-get install tpm2-tools
- Validate basic functionality
compulab@iot-gate-imx8plus:~$ sudo tpm2_getrandom 16
Break-out
Break-out add-on board exposes expansion connector signals on 100-mil headers.
The IOT-GATE-IMX8PLUS / SBC-IOT-IMX8PLUS Debian Linux image contains iot-gate-imx8plus-brkout_pwm_gpio.dtb device tree.
It provides break-out add-on board usage example by configuring:
- 2x PWMs
- 4x GPIOs
- 1x I2C
Interface/Bus | Name in Linux | Signal Name | Channel/Offset | Header-Offset |
PWM3 | pwmchip0 | PWM3_OUT | 0 | P5-09 |
PWM4 | pwmchip1 | PWM4_OUT | 0 | P5-07 |
GPIO5 | gpiochip4 | GPIO5_IO10 | 10 | P5-13 |
GPIO5_IO11 | 11 | P5-11 | ||
GPIO5_IO12 | 12 | P5-14 | ||
GPIO5_IO13 | 13 | P5-15 | ||
I2C5 | i2c-4 | I2C5_SDA | P5-08 | |
I2C5_SCL | P5-10 |
PWM
The following example demonstrates how to use pwmchip0 from Linux shell.
- Boot Linux kernel with iot-gate-imx8plus-brkout_pwm_gpio.dtb device tree
- Export PWM channel 0 on pwmchip0:
echo "0" | sudo tee -a /sys/class/pwm/pwmchip0/export
- Setup PWM signal period of 100usec and duty cycle of 30%:
echo 100000 | sudo tee -a /sys/class/pwm/pwmchip0/pwm0/period
echo 30000 | sudo tee -a /sys/class/pwm/pwmchip0/pwm0/duty_cycle
- Enable PWM signal:
echo 1 | sudo tee -a /sys/class/pwm/pwmchip0/pwm0/enable
- Disable PWM signal:
echo 0 | sudo tee -a /sys/class/pwm/pwmchip0/pwm0/enable
- Un-export PWM channel 0 on pwmchip0:
echo "0" | sudo tee -a /sys/class/pwm/pwmchip0/unexport
RTC
IOT-GATE-IMX8PLUS / SBC-IOT-IMX8PLUS RTC is implemented with the AM1805 real-time clock (RTC) chip.
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:
compulab@iot-gate-imx8plus:~$ sudo hwclock 2022-08-04 12:38:10.577874+00:00
- To set the date and write it into the RTC do the following:
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
Watchdog
IOT-GATE-IMX8PLUS / SBC-IOT-IMX8PLUS watchdog function is implemented with the i.MX8M Plus watchdog.
By default watchdog is not configured.
compulab@iot-gate-imx8plus:~$ systemctl show | grep RuntimeWatchdog
RuntimeWatchdogUSec=0
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
- Reboot the device
- Verify watchdog configuration
compulab@iot-gate-imx8plus:~$ systemctl show | grep RuntimeWatchdog
RuntimeWatchdogUSec=10s
Watchdog testing
- Run the following command to simulate kernel panic:
compulab@iot-gate-imx8plus:~$ sudo su
root@iot-gate-imx8plus:/home/compulab# echo "c" > /proc/sysrq-trigger
- As a result, the watchdog is not fed and the system reboots after 10 sec.
LEDs
IOT-GATE-IMX8PLUS / SBC-IOT-IMX8PLUS features two user Bi-Color (Red + Green) LEDs found on front panel.
LEDs are controlled via GPIO pins and can be accessed via sysfs interface.
- LEDs are referred to as Green_1, Red_1, Green_2 and Red_2
- Choose a LED (LED2 Red in this example):
compulab@iot-gate-imx8plus:~$ LED=Red_2
- Turn the LED ON
compulab@iot-gate-imx8plus:~$ echo "1" | sudo tee -a /sys/class/leds/${LED}/brightness
- Turn the LED OFF
compulab@iot-gate-imx8plus:~$ echo "0" | sudo tee -a /sys/class/leds/${LED}/brightness
- Set LED's trigger
compulab@iot-gate-imx8plus:~$ echo "heartbeat" | sudo tee -a /sys/class/leds/${LED}/trigger