View source for CL-SOM-iMX8Plus: Yocto Linux: How-To Guide

=Device Tree=
The current release come with these dtb files:
{| class="wikitable" style="text-align:left;"
|-
| align="" | '''DTB''' 
| align="" | '''HW Feature''' 
| align="" | '''Jumpers'/Interface Settings'''
|-
| align="" |som-imx8m-plus.dtb
| align="" |default hardware configuration; mipi dsi, lvds and hdmi enabled
|-
| align="" |som-imx8m-plus_mipi-csi1.dtb
| align="" |default hardware configuration + mipi csi1 enabled + ar1335_af sensor on the P48;
| align="" |E18 is on
|-
| align="" |som-imx8m-plus_mipi-csi2.dtb
| align="" |default hardware configuration + mipi csi2 enabled + ar1335_af sensor on the P47;
| align="" |E23 is on
|-
| align="" |som-imx8m-plus-usbdev.dtb
| align="" |default hardware configuration + USB1 as a peripheral;
| align="" |J5 is in use
|-
| align="" |som-imx8m-plus-hdmi.dtb
| align="" |default hardware configuration w/out lvds and mipi dsi; hdmi display only;
| align="" |P14 is in use
|-
| align="" |som-imx8m-plus-lvds.dtb
| align="" |default hardware configuration w/out hdmi and mipi dsi; lvds display only;
| align="" |P11/P5 lvds iface/touch is in use
|-
| align="" |som-imx8m-plus-mipi.dtb
| align="" |default hardware configuration w/out hdmi and lvds; mipi dsi display only;
| align="" |P22/P45 mipi iface/touch is in use
|-
| align="" |som-imx8m-plus_mipi-csi1-imx219.dtb
| align="" |default hardware configuration + mipi csi1 enabled + imx219 sensor on the P49;
| align="" |E18 is off
|-
|}

==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:
{| class="wikitable" style="text-align:left;"
|-
| align="" | '''Environment''' 
| align="" | '''Command''' 
|-
| align="" |U-Boot
| align="" |setenv fdtfile <fdt_file_name>; saveenv;
|-
| align="" |Linux
| align="" |cl_setenv fdtfile <fdt_file_name>
|-
|}
* GRUB environment (if the image was created with the meta-compulab-uefi layer)
{| class="wikitable" style="text-align:left;"
|-
| align="" | '''Environment''' 
| align="" | '''Command/Procedure''' 
|-
| align="" |GRUB Boot Menu
| align="" |Goto "Advanced Boot Options" and choose a device tree from the provided dtb list.
|-
| align="" |Linux
| align="" |grub-editenv /boot/EFI/BOOT/grubenv set fdtfile=<fdt_file_name>
|-
|}

= Serial Console =
CL-SOM-iMX8Plus provides serial console on UART2.</br>
SB-iMX8Plus evaluation carrier-board exposes the console UART via CP2104 serial-to-USB bridge on connector [[CL-SOM-iMX8Plus: Evaluation Kit: Hardware Guide#Connector_Locations | '''P13''']].
== Connecting to a host PC ==
# Use a micro-USB cable to connect the console connector '''P13''' 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 CL-SOM-iMXPlus 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
# 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>

=Display=
CL-SOM-iMX8Plus evaluation kit supports three types of display interfaces: MIPI-DSI, LVDS and HDMI.</br>
All interfaces are enabled in the default '''som-imx8m-plus.dtb''' device tree file.

==MIPI-DSI==
The CL-SOM-iMX8Plus evaluation kit includes the Startec KD050HDFIA 5" MIPI-DSI LCD panel. 

Connect the MIPI-DSI display to connectors [[CL-SOM-iMX8Plus: Evaluation Kit: Hardware Guide#Connector_Locations | '''P22''' and '''P45''']] on the SB-iMX8Plus carrier-board.

The Linux device node for the MIPI-DSI display:
 /sys/class/drm/card0/card0-DSI-1/
This device node contains information about the display, such as its supported modes and its current configuration.

==LVDS==
SB-iMX8Plus supports direct connection with the Startec KD070HDTLA020 7" LVDS LCD panel.</br>
Connect the display data cable to connector [[CL-SOM-iMX8Plus: Evaluation Kit: Hardware Guide#Connector_Locations | '''P11''']].
Connect the display touch-panel cable to connector [[CL-SOM-iMX8Plus: Evaluation Kit: Hardware Guide#Connector_Locations | '''P5''']].

==HDMI==

SB-iMX8Plus supports HDMI output on connector [[CL-SOM-iMX8Plus: Evaluation Kit: Hardware Guide#Connector_Locations | '''P14''']]. Connect to standard monitor using an HDMI cable.

==Display Manager==
CL-SOM-iMX8Plus Yocto uses Weston as the default display manager. It can be configured in ''/etc/xdg/weston/weston.ini''.</br>
For example the transform setting can be set to rotate-90, rotate-180, rotate-270, or commented out.</br>
In order to apply the configuration, you need to restart the weston display manager:
 systemctl stop weston
 systemctl start weston

=CAN bus=
CL-SOM-iMX8Plus 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 {{filename|iproute2}} utilities.

* To make sure the right '''ip''' utility is used, run:
<pre>
ip -V
ip utility, iproute2-v5.7.0-77-gb687d1067169 
</pre>
* Configure both CAN interface bit-rate to 1 Mbit/sec:
<pre>
ip link set can0 type can bitrate 1000000
ip link set can1 type can bitrate 1000000
</pre>
* Enable the CAN interface:
<pre>
ip link set can0 up
ip link set can1 up
</pre>

==Send/Receive packets==
Use {{filename|cansend}} and {{filename|candump}} utilities to send and receive packets via CAN interface.

* Send standard CAN frame (on the first device):
<pre>
cansend can0 111#1122334455667788
</pre>

* Send extended CAN frame (on the first device):
<pre>
cansend can0 11111111#1122334455667788
</pre>

* CAN frames (extended mode) generator, random payload, interval between two successive flames 50 msec:
<pre>
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
...
</pre>

* Dump all received data frames as well as error frames (on the second device):
<pre>
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
...
</pre>

= WiFi =

CL-SOM-iMX8Plus features 802.11ac wireless connectivity solution implemented with an NXP 88W8997 module.

== WiFi Initialization ==
WiFi requires no user interaction for being configured.
* The driver gets loaded automatically.<br>Use this command to show the loaded drivers:
 '''lsmod | grep mwifiex'''
<pre>
mwifiex_sdio           40960  0
mwifiex               274432  1 mwifiex_sdio
</pre>
* The WiFi driver can be loaded manually:
 '''modprobe mwifiex'''
 '''modprobe mwifiex_sdio'''
<pre>
               mwifiex_sdio mmc0:0001:1: info: FW download over, size 623240 bytes
               mwifiex_sdio mmc0:0001:1: WLAN FW is active
               mwifiex_sdio mmc0:0001:1: info: MWIFIEX VERSION: mwifiex 1.0 (16.68.1.p197) 
               mwifiex_sdio mmc0:0001:1: driver_version = mwifiex 1.0 (16.68.1.p197) 
</pre>
* Browse the WiFi module configuration:
 '''iwconfig mlan0'''
<pre>
mlan0     IEEE 802.11  ESSID:off/any  
          Mode:Managed  Access Point: Not-Associated   Tx-Power=0 dBm   
          Retry short limit:9   RTS thr=2347 B   Fragment thr=2346 B   
          Encryption key:off
          Power Management:on
</pre>
* Activate the interface:
 '''ifconfig mlan0 up'''
* Sample WiFi scanning:
 '''iw mlan0 scan'''
The output will show the list of Access Points and Ad-Hoc cells in range.
For more information about connecting to wireless networks and tuning WiFi interfaces refer to “wpa_supplicant” and “wireless-tools” man pages.

== wpa_supplicant ==
* Create a {{cmd|wpa_supplicant}} configuration file:
<pre>
cat << eof > /etc/wpa_supplicant.conf
ctrl_interface=/var/run/wpa_supplicant
update_config=1
eof
</pre>
* Issue {{cmd|wpa_supplicant}}:
 '''ifconfig mlan0 up'''
 '''wpa_supplicant -B -Dnl80211 -c /etc/wpa_supplicant.conf -i mlan0'''
* Configuring WiFi connection with {{cmd|wpa_cli}}:
 '''wpa_cli'''
<pre>
Selected interface 'mlan0'

Interactive mode

> scan
> scan_results 
bssid / frequency / signal level / flags / ssid
b8:08:cf:a0:7e:f4       5240    -83     [WPA2-PSK-CCMP][ESS]    MYSSID
> add_network
0
> set_network 0 ssid "MYSSID"
> set_network 0 psk "passphrase"
> enable_network 0
> save_config
> quit
</pre>
* Browse the '''''/etc/wpa_supplicant.conf''''':
 '''cat /etc/wpa_supplicant.conf'''
<pre>
ctrl_interface=/var/run/wpa_supplicant
update_config=1

network={
        ssid="MYSSID"
        psk="passphrase"
}
</pre>
* Get an ip-address:
 '''udhcpc -i mlan0'''
<pre>
udhcpc: started, v1.33.1
udhcpc: sending discover
udhcpc: sending select for 172.16.11.28
udhcpc: lease of 172.16.11.28 obtained, lease time 7181
/etc/udhcpc.d/50default: Adding DNS 172.16.11.1
</pre>
* Get the connection status:
 '''wpa_cli status'''
<pre>
Selected interface 'mlan0'
bssid=b8:08:cf:a0:7e:f4
freq=5240
ssid=MYSSID
id=0
mode=station
pairwise_cipher=CCMP
group_cipher=CCMP
key_mgmt=WPA2-PSK
wpa_state=COMPLETED
ip_address=172.16.11.28
p2p_device_address=ec:2e:98:d1:03:f7
address=ec:2e:98:d1:03:f7
uuid=3cb04c02-017b-5df7-af29-69f15c7449ed
</pre>


= Bluetooth =
CL-SOM-iMX8Plus features bluetooth connectivity solution implemented with an NXP 88W8997 module.<br>

{{Note|Before working with Bluetooth, please ensure that Bluetooth antenna is connected to the SOM.}}


To start '''bluetoothctl''' use the following command:
<pre>
bluetoothctl
</pre>

To start the scan process use the following commands:
<pre>
[bluetooth]# default-agent
[bluetooth]# power on
[bluetooth]# scan on
</pre>

Bluetooth device should be turned on and visible. Its MAC-adress and name should appear in '''bluetoothctl''' in following format:
<pre>
[CHG] Device AA:BB:CC:DD:EE:FF Name: Device_Name
</pre>

To pair with the Bluetooth device use the following command:
<pre>
pair AA:BB:CC:DD:EE:FF
</pre>

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

To quit '''bluetoothctl''' use the following command:
<pre>
[Device_Name]# quit
</pre>

=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
<pre>
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
</pre>
* procfs
<pre>
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-
</pre>

===Switch between the available output===
* cl-oselect allows select an output device:
<pre>
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
</pre>

===Audio playback===
* gplay-1.0 allows playing back media files:
<pre>
gplay-1.0 /path/to/media.file
</pre>

==Video Playback==
{{note|The operation below requires '''root''' access.}}

CL-SOM-iMX8Plus 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
<pre>
gst-play /path/to/1.mov
</pre>

* gplay-1.0
<pre>
gplay-1.0 /path/to/1.mov
</pre>

* gst-launch
This method is for advanced users. Please study this document before the start: [https://raw.githubusercontent.com/compulab-yokneam/Documentation/master/pdfs/i.MX8GStreamerUserGuide.pdf i.MX8GStreamerUserGuide.pdf]
<pre>
gst-launch-1.0 -v filesrc location=/path/to/1.mov ! qtdemux name=d.video_0 ! h264parse ! avdec_h264 ! autovideosink
</pre>

==Video Capturing==
{{note|The operation below requires '''root''' access.}}

===Requirements===
* hw: an sensor is connected to either P47 (MIPI_CSI2) or P48+E18 (MIPI_CSI1) port
* sw: a correct device tree is in use:
{| class="wikitable" style="text-align:left;"
|-
| align="" | '''Sensor'''
| align="" | '''CSI1 device tree'''
| align="" | '''CSI2 device tree''' 
| align="" | '''Capture Driver'''
| align="" | '''Device Name'''
|-
| align="" |'''ar1335_af'''
| align="" |som-imx8m-plus_mipi-csi1.dtb
| align="" |som-imx8m-plus_mipi-csi2.dtb
| align="" |ISI
| align="" |/dev/video0
|-
| align="" |'''ar1335'''
| align="" |som-imx8m-plus_mipi-csi1-ar1335-mcu.dtb
| align="" |-
| align="" |ISI
| align="" |/dev/video0
|-
| align="" |'''ar0234'''
| align="" |som-imx8m-plus_mipi-csi1-ar0234.dtb
| align="" |som-imx8m-plus_mipi-csi2-ar0234.dtb
| align="" |ISI
| align="" |/dev/video0
|-
| align="" |'''imx219'''
| align="" |som-imx8m-plus_mipi-csi1-imx219.dtb
| align="" |-
| align="" |ISP
| align="" |/dev/video2
|-
|}
* sw: the '''mxc-isi-cap''' is registered:

===Discovery a capture device===
* ISI
<pre>
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
</pre>
* ISP
<pre>
v4l2-ctl --list-devices
 ():
	/dev/v4l-subdev0
	/dev/v4l-subdev2
	/dev/v4l-subdev3

 (csi0):
	/dev/v4l-subdev1

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

VIV (platform:viv0):
	/dev/video2

vsi_v4l2dec (platform:vsi_v4l2dec):
	/dev/video1

vsi_v4l2enc (platform:vsi_v4l2enc):
	/dev/video0

viv_media (platform:vvcam-video):
	/dev/media1

</pre>

For hardware setup and camera connection instructions please refer to CL-SOM-iMX8Plus Hardware Guide.

===Examples===

Please set a correct '''capture_device''' environment variable.
{| class="wikitable" style="text-align:left;"
|-
| align="" | '''Capture Driver'''
| align="" | '''Device Name Environment Variable'''
|-
| align="" |ISI
| align="" |export capture_device=/dev/video0
|-
| align="" |ISP
| align="" |export capture_device=/dev/video2
|-
|}


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.
<pre>
gst-launch-1.0 v4l2src device=${capture_device} ! 'video/x-raw,width=1280,height=720,format=NV12' ! vpuenc_h264 ! filesink location=/path/to/1.mov
</pre>

* waylandsink
Output to wayland surface.
<pre>
gst-launch-1.0 v4l2src device=${capture_device} ! 'video/x-raw,width=1280,height=720,format=NV12' ! waylandsink window-width=1280 window-height=720
</pre>
* autovideosink
Wrapper video sink for automatically detected video sink.
<pre>
gst-launch-1.0 v4l2src device=${capture_device} ! 'video/x-raw,width=1280,height=720,format=NV12' ! autovideosink
</pre>

* Single Image Capturing
<pre>
gst-launch-1.0 v4l2src device=${capture_device} num-buffers=1 ! jpegenc ! filesink location=single_buffer.jpg
</pre>

==Video streaming==
{{note|The operation below requires '''root''' access.}}
The following command should be executed on CL-SOM-iMX8Plus to start video streaming:
 gst-launch-1.0 v4l2src device=${capture_device} ! 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=
{{note|The operation below requires '''root''' access.}}

CL-SOM-iMX8Plus features suspend mode, which allows to minimize power consumption. 

The following command should be used to enter suspend mode:
<pre>
echo mem >/sys/power/state
</pre>

To resume normal operation press shortly the '''Power On''' button '''SW5'''.

=CPU frequency=
{{note|The operation below requires '''root''' access.}}
==CPU frequency current settings==
Execute the following command to get the current settings:
<pre>
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
</pre>

==Changing the scaling governor==
Execute the following command to change the scaling governor:
<pre>
echo performance > /sys/devices/system/cpu/cpufreq/policy0/scaling_governor
</pre>

Where '''perfomance''' is name of the scaling governor.

Execute the following command to see available scaling governors:
<pre>
cat /sys/devices/system/cpu/cpufreq/policy0/scaling_available_governors
</pre>

Execute the following command to see current scaling governor:
<pre>
cat /sys/devices/system/cpu/cpufreq/policy0/scaling_governor
</pre>

==Changing CPU frequency==
{{note|CPU frequency can be changed only when the scaling governoris set to '''userspace'''.}}
Execute the following command to set CPU frequency:
<pre>
echo 1200000 > /sys/devices/system/cpu/cpufreq/policy0/scaling_setspeed
</pre>

'''1200000''' is one of the available CPU frequencies.

Execute the following command to see available CPU frequencies:
<pre>
cat /sys/devices/system/cpu/cpufreq/policy0/scaling_available_frequencies
</pre>

Execute the following command to see current CPU frequency:
<pre>
cat /sys/devices/system/cpu/cpufreq/policy0/cpuinfo_cur_freq
</pre>

=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:
<pre>
cat /sys/class/thermal/thermal_zone0/temp
</pre>

=RTC=
There two rtc on the device:

==rtc0 (snvs-rtc-lp)==
* System information
<pre>
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
</pre>

* Wake up:
This rtc can be used as a wake up source, as a result an '''rtcwakeup''' can be used with this device:
<pre>
rtcwake --device /dev/rtc0 -s 5 -m mem
</pre>

==rtc1 (ab1805)==
* System information
<pre>
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
</pre>

* Set the date and write it into the RTC:
<pre>
date -s "12 SEP 2019 10:00:00"

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

* Read the RTC time and date:
<pre>
hwclock --show --rtc /dev/rtc1

Thu Sep 12 10:00:48 2019  0.000000 seconds
</pre>


= Device Serial Number =
Product information is stored in on-board EEPROM.<br>
* To read the product serial number, issue the folowing command:
<pre>
compulab@som-imx8plus:~$ cat /proc/device-tree/product-sn
</pre>
* To read the product configuration part number, issue the following command:
<pre>
compulab@som-imx8plus:~$ cat /proc/device-tree/product-options
</pre>

=See Also=
*[[CL-SOM-iMX8Plus: Evaluation Kit: Getting Started | Getting started with CL-SOM-iMX8Plus Evaluation Kit]] <br>
* [[CL-SOM-iMX8Plus: Evaluation Kit: Hardware Guide|CL-SOM-iMX8Plus eval-kit hardware guide]]
[[Category:Yocto]]
[[Category:CL-SOM-iMX8Plus]]