Device Tree

Available Device Tree

The current release come with these dtb files:

DTB	HW Feature	Jumpers' Settings
ucm-imx8m-plus.dtb	default hardware configuration; mipi dsi, lvds and hdmi enabled
ucm-imx8m-plus_mipi-csi1.dtb	default hardware configuration + mipi csi1 enabled + ar1335_af sensor on the P48;	E18 is on
ucm-imx8m-plus_mipi-csi2.dtb	default hardware configuration + mipi csi2 enabled + ar1335_af sensor on the P47;	E16 is off
ucm-imx8m-plus-usbdev.dtb	default hardware configuration + USB1 as a peripheral;	J5 is in use
ucm-imx8m-plus-hdmi.dtb	default hardware configuration w/out lvds and mipi dsi; hdmi display only;	P14 is in use
ucm-imx8m-plus-lvds.dtb	default hardware configuration w/out hdmi and mipi dsi; lvds display only;	P11/P5 lvds iface/touch is in use
ucm-imx8m-plus-mipi.dtb	default hardware configuration w/out hdmi and lvds; mipi dsi display only;	P22/P45 mipi iface/touch is in use
ucm-imx8m-plus-rpmsg.dtb	default hardware configuration + rpmgs on for M7;
ucm-imx8m-plus-ldo4.dtb	default hardware configuration + ldo4 bypass settings from U-Boot;

Set a 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	cl_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/EFI/BOOT/grubenv set fdt_file=<fdt_file_name>

U-Boot

Basic commands

Restore default boot environment:

env default -a

List boot candidates:

printenv bootlist

Get device tree:

printenv fdtfile

LDO4 - secondary RGMII voltage control

PMIC LDO4 controls voltage rail that powers secondary RGMII signal group.
By default LDO4 is configured for 1.8V operation. In order to control LDO4 settings and have them passed correctly to the Linux kernel, use the command and device tree described below.

The device tree to use:

device tree	U-Boot command
ucm-imx8m-plus-ldo4.dtb	setenv fdtflie ucm-imx8m-plus-ldo4.dtb

ldo4 command:

help ldo4

ldo4 modes:

mode	commands
1v8 mode	ldo4 18; boot
3v3 mode	ldo4 33; boot
off mode	ldo4 0;boot

Gstreamer

Yocto Linux uses Gstreamer as a default multimedia framework. Here are some useful Gstreamer features:

Execute the following command to check all the source options:

gst-inspect-1.0 | grep source

Execute the following command to check all the sink options:

gst-inspect-1.0 | grep sink

Analog Audio

List of available sound cards

aplay

aplay -l

**** List of PLAYBACK Hardware Devices ****
card 0: imxaudioxcvr [imx-audio-xcvr], device 0: XCVR PCM snd-soc-dummy-dai-0 []
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: audiohdmi [audio-hdmi], device 0: imx8 hdmi i2s-hifi-0 []
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 2: ucmimx8mplus [ucm-imx8m-plus], device 0: 30c30000.sai-wm8731-hifi wm8731-hifi-0 []
  Subdevices: 1/1
  Subdevice #0: subdevice #0

procfs

cat /proc/asound/cards

 0 [imxaudioxcvr   ]: imx-audio-xcvr - imx-audio-xcvr
                      compulab-ucm_imx8m_plus-
 1 [audiohdmi      ]: audio-hdmi - audio-hdmi
                      compulab-ucm_imx8m_plus-
 2 [ucmimx8mplus   ]: ucm-imx8m-plus - ucm-imx8m-plus
                      compulab-ucm_imx8m_plus-

Switch between the available output

cl-oselect allows select an output device:

cl-oselect

1) alsa_output.platform-sound-hdmi.stereo-fallback
2) alsa_output.platform-sound-xcvr.iec958-stereo
3) alsa_output.platform-sound.analog-stereo
4) <<
Sound sink [ alsa_output.platform-sound.analog-stereo ] > 3

Audio playback

gplay-1.0 allows playing back media files:

gplay-1.0 /path/to/media.file

USB

i.MX8M Plus SoC is equipped with two dual-role USB3.0 controllers and PHYs.
USB1 can be configured as host or device, while the USB2 is configured permanently for host mode.

USB1 mode switch

The SOM is able to work as a host or as a device. Due to a HW limitation the mode switch does not work automatically yet.

host
The device works in a host mode unless the ucm-imx8m-plus-usbdev.dtb is loaded.
device
The device works in a device mode when the ucm-imx8m-plus-usbdev.dtb is loaded.
In this mode the SOM can work in one of the usb device mode:

USB device mode	Command/Procedure
usb serial device	modprobe g_serial
usb network device	modprobe g_ether
usb mass storage device	modprobe g_mass_storage file=/dev/sdX

Video Playback

The operation below requires root access.

UCM-iMX8M-Plus features 1080p60 H.264, VP8 video decoding capabilities. Before starting video playback, please, ensure that the display is connected to the board.

The following commands can be used to start video playback (1.mov is a media file):

gst-play

gst-play /path/to/1.mov

gplay-1.0

gplay-1.0 /path/to/1.mov

gst-launch

This method is for advanced users. Please study this document before the start: i.MX8GStreamerUserGuide.pdf

gst-launch-1.0 -v filesrc location=/path/to/1.mov ! qtdemux name=d.video_0 ! h264parse ! avdec_h264 ! autovideosink

Video Capturing

The operation below requires root access.

Requirements

hw: an ar1335 sensor is connected to either P47 (MIPI_CSI2) or P49+E18 (MIPI_CSI1) port
sw: a correct device tree is in use:

Interface	Device Stree
MIPI_CSI1	ucm-imx8m-plus_mipi-csi1.dtb
MIPI_CSI2	ucm-imx8m-plus_mipi-csi2.dtb

sw: the mxc-isi-cap is registered:

v4l2-ctl --list-devices

 ():
        /dev/v4l-subdev0

mxc-isi-cap (platform:32e00000.isi:cap_devic):
        /dev/video0

FSL Capture Media Device (platform:mxc-md):
        /dev/media0

For hardware setup and camera connection instructions please refer to UCM-iMX8M-Plus Hardware Guide.

Examples

The following commands should be used to start video capturing:

filesink

Write stream to a file. In this example the encoded output gets saved in the 1.mov media file.

gst-launch-1.0 v4l2src device=/dev/video0 ! 'video/x-raw,width=1280,height=720,format=NV12' ! vpuenc_h264 ! filesink location=/path/to/1.mov

waylandsink

Output to wayland surface.

gst-launch-1.0 v4l2src device=/dev/video0 ! 'video/x-raw,width=1280,height=720,format=NV12' ! waylandsink window-width=1280 window-height=720

autovideosink

Wrapper video sink for automatically detected video sink.

gst-launch-1.0 v4l2src device=/dev/video0 ! 'video/x-raw,width=1280,height=720,format=NV12' ! autovideosink

Single Image Capturing

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

Video streaming

The operation below requires root access.

The following command should be executed on UCM-iMX8M-Plus to start video streaming:

gst-launch-1.0 v4l2src device=/dev/video0 ! video/x-raw, width=640, height=480 ! jpegenc ! udpsink host=127.0.0.1 port=1234

127.0.0.1 is the IP address of the host PC, and 1234 is the host PC port.

The following command should be executed on host PC (Linux) to receive the video stream:

gst-launch-1.0 udpsrc port=1234 ! jpegdec ! autovideosink

1234 is the host PC port.

Suspend / Resume

The operation below requires root access.

UCM-iMX8M-Plus 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 Power On button SW5.

CPU frequency

The operation below requires root access.

CPU frequency current settings

Execute the following command to get the current settings:

grep -ir . /sys/devices/system/cpu/cpufreq/policy0/ 2>/dev/null

/sys/devices/system/cpu/cpufreq/policy0/scaling_min_freq:1200000
/sys/devices/system/cpu/cpufreq/policy0/scaling_available_governors:conservative ondemand userspace powersave performance schedutil 
/sys/devices/system/cpu/cpufreq/policy0/cpuinfo_cur_freq:1200000
/sys/devices/system/cpu/cpufreq/policy0/scaling_governor:ondemand
/sys/devices/system/cpu/cpufreq/policy0/cpuinfo_max_freq:1600000
/sys/devices/system/cpu/cpufreq/policy0/scaling_available_frequencies:1200000 1600000 
/sys/devices/system/cpu/cpufreq/policy0/related_cpus:0 1 2 3
/sys/devices/system/cpu/cpufreq/policy0/scaling_cur_freq:1200000
/sys/devices/system/cpu/cpufreq/policy0/scaling_setspeed:<unsupported>
/sys/devices/system/cpu/cpufreq/policy0/stats/trans_table:   From  :    To
/sys/devices/system/cpu/cpufreq/policy0/stats/trans_table:         :   1200000   1600000 
/sys/devices/system/cpu/cpufreq/policy0/stats/trans_table:  1200000:         0        65 
/sys/devices/system/cpu/cpufreq/policy0/stats/trans_table:  1600000:        65         0 
/sys/devices/system/cpu/cpufreq/policy0/stats/total_trans:130
/sys/devices/system/cpu/cpufreq/policy0/stats/time_in_state:1200000 643
/sys/devices/system/cpu/cpufreq/policy0/stats/time_in_state:1600000 474
/sys/devices/system/cpu/cpufreq/policy0/affected_cpus:0 1 2 3
/sys/devices/system/cpu/cpufreq/policy0/scaling_max_freq:1600000
/sys/devices/system/cpu/cpufreq/policy0/cpuinfo_transition_latency:182000
/sys/devices/system/cpu/cpufreq/policy0/scaling_driver:cpufreq-dt
/sys/devices/system/cpu/cpufreq/policy0/cpuinfo_min_freq:1200000

Changing the scaling governor

Execute the following command to change the scaling governor:

echo performance > /sys/devices/system/cpu/cpufreq/policy0/scaling_governor

Where perfomance is name of the scaling governor.

Execute the following command to see available scaling governors:

cat /sys/devices/system/cpu/cpufreq/policy0/scaling_available_governors

Execute the following command to see current scaling governor:

cat /sys/devices/system/cpu/cpufreq/policy0/scaling_governor

Changing CPU frequency

CPU frequency can be changed only when the scaling governoris set to userspace.

Execute the following command to set CPU frequency:

echo 1200000 > /sys/devices/system/cpu/cpufreq/policy0/scaling_setspeed

1200000 is one of the available CPU frequencies.

Execute the following command to see available CPU frequencies:

cat /sys/devices/system/cpu/cpufreq/policy0/scaling_available_frequencies

Execute the following command to see current CPU frequency:

cat /sys/devices/system/cpu/cpufreq/policy0/cpuinfo_cur_freq

CPU temperature

i.MX8M-Plus 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

RTC

There two rtc on the device:

rtc0 (snvs-rtc-lp)

System information

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

P: /devices/platform/soc@0/30000000.bus/30370000.snvs/30370000.snvs:snvs-rtc-lp/rtc/rtc0
N: rtc0
L: -100
S: rtc
E: DEVPATH=/devices/platform/soc@0/30000000.bus/30370000.snvs/30370000.snvs:snvs-rtc-lp/rtc/rtc0
E: DEVNAME=/dev/rtc0
E: MAJOR=251
E: MINOR=0
E: SUBSYSTEM=rtc
E: USEC_INITIALIZED=8188223
E: DEVLINKS=/dev/rtc

Wake up:

This rtc 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

rtc1 (ab1805)

System information

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

P: /devices/platform/soc@0/30800000.bus/30a30000.i2c/i2c-1/1-0069/rtc/rtc1
N: rtc1
L: 0
E: DEVPATH=/devices/platform/soc@0/30800000.bus/30a30000.i2c/i2c-1/1-0069/rtc/rtc1
E: DEVNAME=/dev/rtc1
E: MAJOR=251
E: MINOR=1
E: SUBSYSTEM=rtc

Set the date and write it into the RTC:

date -s "12 SEP 2019 10:00:00"

Thu Sep 12 10:00:00 UTC 2019
hwclock --systohc --rtc /dev/rtc1

Read the RTC time and date:

hwclock --show --rtc /dev/rtc1

Thu Sep 12 10:00:48 2019  0.000000 seconds

Controller–area network (CAN)

UCM-iMX8M-PLUS features two Flexible Controller Area Network (FLEXCAN) modules. The FlexCAN module is a full implementation of the CAN protocol specification, the CAN with Flexible Data rate (CAN FD) protocol, and the CAN 2.0 version B protocol, which supports both standard and extended message frames and long payloads up to 64 bytes, transferred at faster rates (up to 8 Mb/s).

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
ip link set can1 type can bitrate 1000000

Enable the CAN interface:

ip link set can0 up
ip link set can1 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.77.27.81.49.0B
  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#75.81.70.7C.86.79.A7.77
  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-iMX8M-Plus: Yocto Linux: How-To Guide

Contents

Device Tree

Available Device Tree

Set a device tree

U-Boot

Basic commands

LDO4 - secondary RGMII voltage control

Gstreamer

Analog Audio

List of available sound cards

Switch between the available output

Audio playback

USB

USB1 mode switch

Video Playback

Video Capturing

Requirements

Examples

Video streaming

Suspend / Resume

CPU frequency

CPU frequency current settings

Changing the scaling governor

Changing CPU frequency

CPU temperature

RTC

rtc0 (snvs-rtc-lp)

rtc1 (ab1805)

Controller–area network (CAN)

CAN interface configuration

Send/Receive packets

See Also

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