UCM-iMX93: Yocto Linux: How-To Guide

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Device Tree

Available Device Tree Files

The current release includes the following dtb files:

DTB Hardware Configuration and Features Jumpers/Connectors Settings
ucm-imx93.dtb default hardware configuration + mipi dsi display P11/P12 mipi iface/touch is in use
ucm-imx93-lvds.dtb default hardware configuration + lvds display P7/P8 lvds iface/touch is in use
ucm-imx93-headless.dtb default hardware configuration w/out any display

Set device tree

The current release 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 (if the image was created with the meta-compulab-uefi layer)
Environment Command/Procedure
GRUB Boot Menu Goto "Advanced Boot Options" and choose a device tree from the provided dtb list.
Linux grub-editenv /boot/grub/grubenv set fdtfile=<fdt_file_name>

Serial Console

UCM-iMX93 provides serial console on UART1.
SB-UCMIMX93 evaluation carrier-board exposes the console UART via CP2104 serial-to-USB bridge on connector P16.

Connecting to a host PC

  1. Use a micro-USB cable to connect the console connector P16 to a USB port on your host PC.
  2. 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
  3. Identify the host PC interface and port number that will be used for communication with the UCM-iMX93 evaluation kit:
    • 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
  4. Start a terminal emulation program (such as PuTTY on Windows or minicom on Linux).
  5. In the port configuration section of the terminal emulation program select the port identified in previous step and set the following serial port parameters:
Baud Rate Data Bits Stop Bits Parity Flow Control
115200 8 1 none none



The UCM-iMX93 evaluation kit can be optionally supplied with the Startec KD070HDTLA020 7" LVDS LCD panel. Connect the display data cable to connector P7. Connect the display touch-panel cable to connector P8.

LVDS display requires the following device tree: ucm-imx93-lvds.dts.

The Linux device node for the display is described in: arch/arm64/boot/dts/compulab/ucm-imx93-lvds.dtsi.


SB-UCMIMX93 supports direct connection with the Startec KD050HDFIA 5" MIPI-DSI LCD panel.

Connect the MIPI-DSI display to connectors P11 and P12 on the SB-UCMIMX93 carrier-board.

The MIPI-DSI display requires the following device tree: ucm-imx93-mipi.dts.
The MIPI-DSI display is described in the following device tree include file: arch/arm64/boot/dts/compulab/ucm-imx93-mipi.dtsi The Linux device node for the MIPI-DSI display:


This device node contains information about the display, such as its supported modes and its current configuration.

Display Manager

UCM-iMX93 Yocto uses Weston as the default display manager. It can be configured in /etc/xdg/weston/weston.ini.
For example the transform setting can be set to rotate-90, rotate-180, rotate-270, or commented out.
In order to apply the configuration, you need to restart the weston display manager:

systemctl stop weston
systemctl start weston


The UCM-iMX93 evaluation kit supports the e-con e-CAM131_CURB 13MP 4K camera module.
Connect the camera to connector P9 on the SB-UCMIMX93 carrier-board.

Use device tree file: ucm-imx93-mipi-csi.dtb The Linux video device node used for capturing: /dev/video0

Video Capturing

Single image capturing:

gst-launch-1.0 v4l2src num-buffers=1 ! jpegenc ! filesink location=single_buffer.jpg

Output to wayland surface:

gst-launch-1.0 v4l2src device=/dev/video0 ! 'video/x-raw,width=1280,height=720,format=BGRA' ! textoverlay text="CLAB UCM-iMX93" ! waylandsink window-width=1280 window-height=720

To find a pipe element run:

gst-inspect-1.0 | grep sink -i

Detailed information on a specific pipe element:

gst-inspect-1.0 <name>

To learn more please refer to:




UCM-IMX93 features two USB2.0 ports that are derived from the i.MX93 USB sub-system.
On SB-UCMIMX93 evaluation carrier-board USB ports are available on the following connectors:

USB port# HW setting Connector Mode
1 P21 is not used type-A J5 host
1 P21 connected to USB host micro-USB P21 device
2 jumper E11 is open type-A J6 host
2 jumper E11 is closed mini-PCIe P18 host

USB #1 in device mode

USB #1 port can be operated in device mode when connected to a host machine using connector P21.
Available gadgets for the UBS #1 in device mode:

USB gadget SOM command
usb serial device modprobe g_serial
usb network device modprobe g_ether
usb mass storage device modprobe g_mass_storage file=/dev/sdX

CAN bus

UCM-iMX93 features two Flexible Controller Area Network (FLEXCAN) modules. SB-UCMIMX93 evaluation carrier-board exposes one CAN bus interface on connector J21.

CAN interface configuration

It is recommended configure the CAN interface, with the iproute2 utilities.

  • To make sure the right ip utility is used, run:
ip -V
ip utility, iproute2-v5.7.0-77-gb687d1067169 
  • Configure both CAN interface bit-rate to 1 Mbit/sec:
ip link set can0 type can bitrate 1000000
  • Enable the CAN interface:
ip link set can0 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):
cansend can0 111#1122334455667788
  • Send extended CAN frame (on the first device):
cansend can0 11111111#1122334455667788
  • CAN frames (extended mode) generator, random payload, interval between two successive flames 50 msec:
cangen -g 50 -e -D r -v can0

can: raw protocol (rev 20170425)
  can0  03FF0983#D7.61.FF.03.C1.F7.C1.34
  can0  19C34D32#F7.5A.C2.73.AD.0E.3F.0B
  can0  0675E391#2B.2D.D3.49
  can0  13091C55#99.32.EC.
  can0  098D67CF#22.50.AB.48.AD.7F.F4.26
  can0  05263FEC#1B.4C.02.45.6E
  can0  12B30E20#
  can0  1F193DF9#C5
  can0  1EB0B18F#3E.3F.DA.57.C2.FE.73.58
  can0  1E5C64D9#6F.0D.B3.63.6A
  can0  1E1DE3F9#96.48.AC.79.4E.00.27.71
  can0  0E1A11B7#
  can0  05F8FD8B#33.F9.9B.1E.77.3D.1F
  can0  1E155FCD#E6.BA.F8.58.ED.6D.C8.10
  can0  1D91DF9E#5D.29.82.7B.97.1D.AB.5C
  can0  11FB3CDA#14.65.C3
  can0  091352C0#2C.ED
  • Dump all received data frames as well as error frames (on the second device):
candump any,0:0,#FFFFFFFF

  can0  111   [8]  11 22 33 44 55 66 77 88
  can0  11111111   [8]  11 22 33 44 55 66 77 88
  can0  03FF0983   [8]  D7 61 FF 03 C1 F7 C1 34
  can0  19C34D32   [8]  F7 5A C2 73 AD 0E 3F 0B
  can0  0675E391   [4]  2B 2D D3 49
  can0  13091C55   [8]  99 32 EC 77 27 81 49 0B
  can0  098D67CF   [8]  22 50 AB 48 AD 7F F4 26
  can0  05263FEC   [5]  1B 4C 02 45 6E
  can0  12B30E20   [0] 
  can0  1F193DF9   [1]  C5
  can0  1EB0B18F   [8]  3E 3F DA 57 C2 FE 73 58
  can0  1E5C64D9   [5]  6F 0D B3 63 6A
  can0  1E1DE3F9   [8]  96 48 AC 79 4E 00 27 71
  can0  0E1A11B7   [8]  75 81 70 7C 86 79 A7 77
  can0  05F8FD8B   [7]  33 F9 9B 1E 77 3D 1F
  can0  1E155FCD   [8]  E6 BA F8 58 ED 6D C8 10
  can0  1D91DF9E   [8]  5D 29 82 7B 97 1D AB 5C
  can0  11FB3CDA   [3]  14 65 C3
  can0  091352C0   [2]  2C ED


UCM-iMX93 features 802.11ac wireless connectivity solution implemented with an NXP 88W8997 module.
The NetworkManager can be used to manage WiFi interface.

Admolition note.png Before working with WiFi, please ensure that WiFi antenna is connected to the SOM.

Enable/Disable WiFi Interface

  • To enable WiFi interface:
nmcli radio wifi on
  • To disable WiFi interface:
nmcli radio wifi off

Network Scanning

  • Sample WiFi scanning:
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:
nmcli device wifi connect <SSID> password <PASSWORD> name WifiCon
  • Disconnect wireless network:
nmcli connection down WifiCon
  • Connect wireless network again:
nmcli connection up WifiCon

Creating Access Point

In the following example:

  • Replace <SSID> and <PASSWORD> with desired access point parameters:
nmcli device wifi hotspot ssid <SSID> password <PASSWORD> con-name HotspotCon
  • Disable wireless AP:
nmcli connection down HotspotCon
  • Enable wireless AP again:
nmcli connection up HotspotCon


UCM-iMX93 features Bluetooth connectivity implemented with an NXP 88W8997 module.

Admolition note.png Before working with Bluetooth, please ensure that Bluetooth antenna is connected to the SOM.

To start bluetoothctl use the following command:


To start the scan process use the following commands:

[bluetooth]# default-agent
[bluetooth]# power on
[bluetooth]# scan on

Bluetooth device should be turned on and visible. Its MAC-adress and name should appear in bluetoothctl in following format:

[CHG] Device AA:BB:CC:DD:EE:FF Name: Device_Name

To pair with the Bluetooth device use the following command:


Where AA:BB:CC:DD:EE:FF is MAC-adress of the Bluetooth device.

To quit bluetoothctl use the following command:

[Device_Name]# quit

Cellular Modem

UCM-IMX93 Yocto includes support for Quectel EC25 mini-PCIe cellular modem that can be installed into the evaluation kit.

  • Install the modem module into the mini-PCIe socket P18
  • Close jumper E11
  • Connect a cellular antenna to the main antenna connector on the modem
  • Install an active SIM card into SIM socket P20
  • Boot to linux

Run the following command to verify that the modem is detected correctly:

root@ucm-imx93:~# lsusb                                                                                                                                                                                            
Bus 001 Device 002: ID 2c7c:0125 Quectel Wireless Solutions Co., Ltd. EC25 LTE modem                                                                                                                               

root@ucm-imx93:~# mmcli -L                                                                                                                                                                                         
    /org/freedesktop/ModemManager1/Modem/0 [QUALCOMM INCORPORATED] QUECTEL Mobile Broadband Module                                                                                                                 

Obtain <apn> of your sim card company ,e.g. rl.internet

Establish connection:

root@ucm-imx93:~# nmcli connection add type gsm ifname '*' con-name CellularCon apn <apn>
root@ucm-imx93:~# nmcli connection
NAME                UUID                                  TYPE      DEVICE   
CellularCon         a1620622-8588-4349-b3fc-66be79fbbede  gsm       cdc-wdm0 

Allow up to a minute to connect to wireless network and make sure modem state is connected:

root@ucm-imx93:~#mmcli -m 0

To test the wireless interface run:

root@ucm-imx93:~#ping -c 5 dns.google -I wwan0


The following table outlines default UART routing when UCM-iMX93 is used with the SB-UCMIMX93 carrier-board:

UCM-iMX93 port Linux device on SB-UCMIMX93 carrier-board
UART1 /dev/ttyLP0 converted to serial-over-USB debug console, micro-USB connector P16
UART2 /dev/ttyLP1 converted to RS232, DB9 connector P17
UART5 /dev/ttyLP4 routed to 100-mil header P3
UART7 /dev/ttyLP6 converted to RS485, terminal block J22

Example: testing UART5

  • Short pin P3-1 (UART5-RX) with P3-3 (UART5-TX) on SB-UCMIMX93 to create a loop-back.
  • Run the following commands:
stty -F /dev/ttyLP4 1:0:1cb2:0:3:1c:7f:15:4:5:1:0:11:13:1a:0:12:f:17:16:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0
cat /dev/ttyLP4 &
echo hello > /dev/ttyLP4

The "hello" string should appear on the terminal.


The following I2C buses and devices are present when UCM-iMX93 is used with the SB-UCMIMX93 carrier-board:

Device I2C bus in Linux Address HW port in UCM-iMX93
UCM-iMX93 EEPROM 0 0x50 I2C1 (internal)
UCM-iMX93 RTC 0 0x69 I2C1 (internal)
UCM-iMX93 PMIC 1 0x25 I2C2 (internal)
GPIO extender on SB-UCMIMX93 for on-board control signals 2 0x20 I2C3
Camera module control on SB-UCMIMX93 connector P9 2 0x42 I2C3
Touch-screen controller of MIPI-DSI or LVDS panel on SB-UCMIMX93 connector P8 or P12 2 0x5d I2C3

To list all mapped devices:

# ls /proc/device-tree/soc@0/bus@*/i2c@*/*@* -d -w 1                                                                                                         

Note how:

  • each node is appended with its address.
  • I2C buses order corresponds to the order of their addresses.

e.g. to inspect bus 0, in which we have RTC, run:

# i2cdetect -y 0
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:                         -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
50: 50 51 52 53 -- -- -- -- -- -- -- -- -- -- -- -- 
60: -- -- -- -- -- -- -- -- -- UU -- -- -- -- -- -- 
70: -- -- -- -- -- -- -- --                         

In the above output numbers mark unused devices, UU marks a device that is used by a driver.

Indeed we see RTC in use at offset 0x69.

An example how to dump EEPROM contents:

hexdump -C /sys/devices/platform/soc@0/44000000.bus/44340000.i2c/i2c-0/0-0050/eeprom


The following command displays listing of all of SPI devices in the system:

root@ucm-imx93:~# find /proc/device-tree/ -name *spi*|grep soc


The following table outlines default GPIO assignments when UCM-iMX93 is used with the SB-UCMIMX93 carrier-board:

Signal Name On SB-UCMIMX93 GPIO # in Linux
GPIO_IO04 P3-20 32+4
GPIO_IO05 P3-18 32+18
GPIO_IO07 P3-6 32+7
GPIO_IO14 P5-4 32+14
GPIO_IO15 P5-2 32+15
GPIO_IO16 P3-4 32+16

These GPIOs belong to gpiochip0 which numbering space starts at 32. Therefore it is required to add 32 to the GPIO number.
Other signals that are reserved for peripheral controls can be reassigned to function as GPIOs in arch/arm64/boot/dts/compulab/ucm-imx93-pinctrl.dtsi.

Example: controlling pin GPIO_IO16

Exporting the pin in sysfs
Create a file system export entry:

cd /sys/class/gpio/
echo $((32+16)) > export

Now pin GPIO_IO16 is assigned to sysfs. You can view the newly created entry in line 16 by running:

gpioinfo 0

Writing to a pin
Go to GPIO_IO16 sysfs folder:

cd /sys/class/gpio/gpio$((32+16))

Set pin direction to output:

echo out > direction

Set pin value to high or low:

echo 1 > value 
echo 0 > value

Reading from a pin
Go to GPIO_IO16 sysfs folder:

cd /sys/class/gpio/gpio$((32+16))

Set pin direction to input:

echo in > direction

Read the value of the pin from the value file:

cat value

Suspend / Resume

Admolition note.png The operation below requires root access.

UCM-iMX93 features suspend mode, which allows to minimize power consumption.

The following command should be used to enter suspend mode:

echo mem >/sys/power/state

To resume normal operation press shortly the ON/OFF button SW5.

CPU temperature

i.MX93 SoC features an internal temperature sensor which allows to measure the SoC temperature. Execute the following command to read the current CPU temperature:

cat /sys/class/thermal/thermal_zone0/temp


UCM-iMX93 features two RTC devices:

  • i.MX93 internal RTC (rtc0) - can be used as wake-up source
  • AB1805 external RTC (rtc1) - can be used for low current battery powered time keeping

Internal RTC - rtc0

System information:

udevadm info -p /sys/class/rtc/rtc0

P: /devices/platform/soc@0/44000000.bus/44440000.bbnsm/44440000.bbnsm:rtc/rtc/rtc0
N: rtc0
L: -100
S: rtc
E: DEVPATH=/devices/platform/soc@0/44000000.bus/44440000.bbnsm/44440000.bbnsm:rtc/rtc/rtc0
E: DEVNAME=/dev/rtc0
E: MAJOR=251
E: DEVLINKS=/dev/rtc

Wake up:
rtc0 can be used as a wake up source, as a result an rtcwakeup can be used with this device:

rtcwake --device /dev/rtc0 -s 5 -m mem

External RTC - rtc1

System information:

udevadm info -p /sys/class/rtc/rtc1

N: rtc1
L: 0
E: DEVPATH=/devices/platform/soc@0/44000000.bus/44340000.i2c/i2c-0/0-0069/rtc/rtc1
E: DEVNAME=/dev/rtc1
E: MAJOR=251

Set the date and write it into the RTC:

date -s "16 Jun 2023 12:00:00"

Fri 16 Jun 2023 12:00:00
hwclock --systohc --rtc /dev/rtc1

Read the RTC time and date:

hwclock --show --rtc /dev/rtc1

2023-06-16 12:01:37.935876+00:00

Device Serial Number

Product information is stored in on-board EEPROM.

  • To read the product serial number run:
cat /proc/device-tree/product-sn && echo
  • To read the product configuration part number run:
cat /proc/device-tree/product-options && echo

See Also