CL-SOM-iMX8Plus: Yocto Linux: How-To Guide
Contents
Device Tree
The current release come with these dtb files:
| DTB | HW Feature | Jumpers'/Interface Settings |
| som-imx8m-plus.dtb | default hardware configuration; mipi dsi, lvds and hdmi enabled | |
| som-imx8m-plus_mipi-csi1.dtb | default hardware configuration + mipi csi1 enabled + ar1335_af sensor on the P48; | E18 is on |
| som-imx8m-plus_mipi-csi2.dtb | default hardware configuration + mipi csi2 enabled + ar1335_af sensor on the P47; | E23 is on |
| som-imx8m-plus-usbdev.dtb | default hardware configuration + USB1 as a peripheral; | J5 is in use |
| som-imx8m-plus-hdmi.dtb | default hardware configuration w/out lvds and mipi dsi; hdmi display only; | P14 is in use |
| som-imx8m-plus-lvds.dtb | default hardware configuration w/out hdmi and mipi dsi; lvds display only; | P11/P5 lvds iface/touch is in use |
| som-imx8m-plus-mipi.dtb | default hardware configuration w/out hdmi and lvds; mipi dsi display only; | P22/P45 mipi iface/touch is in use |
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 fdtfile=<fdt_file_name> |
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: somimx8mplus [som-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-som_imx8m_plus-
1 [audiohdmi ]: audio-hdmi - audio-hdmi
compulab-som_imx8m_plus-
2 [somimx8mplus ]: som-imx8m-plus - som-imx8m-plus
compulab-som_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
Video Playback
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The operation below requires root access. |
SOM-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 command should be used to start video playback (1.mov is a media file):
gst-launch-1.0 -v filesrc location=1.mov ! h264parse ! avdec_h264 ! autovideosink
Video Capturing
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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 | som-imx8m-plus_mipi-csi1.dtb |
| MIPI_CSI2 | som-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 SOM-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 -v v4l2src ! vpuenc_h264 ! filesink location=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
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The operation below requires root access. |
The following command should be executed on SOM-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
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The operation below requires root access. |
SOM-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
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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
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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)
SOM-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 ...
