Embedded module TQMa8XxS - YOCTO Linux BSP documentation

Play Audio on MB-SMARC-2

A simple test sound can be played with the commandline tool speaker-test.
Headphones or active speakers have to be connected to X18 on MB-SMARC-2.

speaker-test --channels 2 --test wav

You can also play your own audio files using aplay

aplay <file>

e.g.

aplay test.wav

Record Audio via Line-In on MB-SMARC-2

arecord -f cd test.wav

The MB-SMARC-2 provides the CAN interfaces CAN0 and CAN1.

ip link set can0 down
ip link set can0 up type can bitrate 500000 sample-point 0.75 dbitrate 4000000 dsample-point 0.8 fd on
ip link set can1 down
ip link set can1 up type can bitrate 500000 sample-point 0.75 dbitrate 4000000 dsample-point 0.8 fd on

Loopback Test CAN Interface

CAN0 -> CAN1

candump can0&
cansend can1 5A1#11.2233.44556677.88

CAN1 -> CAN0

candump can1&
cansend can0 5A1#11.2233.44556677.88

The STKa8XxS supports DVFS (dynamic voltage and frequency scaling, by default the governor ondemand is set. Governors are power schemes for the CPU. Only one may be active at a time.

You can change the actual governor with the following command:

cpufreq-set -g <governor>
(e.g. cpufreq-set -g performance)

Disable CPU Core temporarily

At runtime it is possible to disable multiple CPU cores via the Linux sysfs. On a system that has four CPU cores, the maximum of three cores can be disabled. To disable the a CPU core value 0 must be written to the CPU core specific file /sys/devices/system/cpu/cpu<N>/online where <N> is the number of the Core, the counting starts at zero.
e.g. disable CPU core 4:

echo 0 > /sys/devices/system/cpu/cpu3/online

To check which CPU core(s) are currently enabled the following command can be used:

grep "processor" /proc/cpuinfo

The CPU core can be enabled again by writing the value 1 to /sys/devices/system/cpu/cpu<N>/online.

e.g. enable CPU core 4:

echo 1 > /sys/devices/system/cpu/cpu3/online

setenv addcpu maxcpus=${cpu_num}

setenv cpu_num 2

The STKa8XxS Starterkit provides two Gigabit Ethernet interfaces.

setenv ipaddr <ipaddr> 
(e.g.: setenv ipaddr 192.168.100.111)
setenv netmask <netmask> 
(e.g.: setenv netmask 255.255.255.0)

ip link set eth0 up

ip link set eth0 down

ip addr show eth0

 
ip -s link show eth0 

ip addr add 192.168.1.100/24 dev eth0

ip -s link

ip route add default via 192.168.1.1 dev eth0

udhcpc -i eth1 

Run GPU benchmark with connected display and loaded device tree in fullscreen mode:

glmark2-es2-wayland --fullscreen

An overview of the onboard i2c devices is available here

i2c dev 0

i2c probe

i2cdetect 16

TQ offers an optional LVDS Display kit for the STKa8XxS. Each Display can be used on its own by using the corresponding device tree. To allow reusage, the support for each display is separated in a dtsi fragment.

Note: For the backlight on the MB-SMARC-2 you can bridge X14 pin 1 and 2 to provide 12V.

To bring up the display the U-Boot environment has to be adapted accordingly.

1. Interrupt boot process in U-boot
2. Set U-Boot environment variable fdt_file with the command setenv fdt_file <device tree> (e.g. setenv fdt_file imx8qxp-mb-smarc-2-lvds0-tm070jvhg33.dtb)
3. Save the envrionment by executing the saveenv command

To set the hardware clock to the actual time and date use the following commands:

date -s [YYYY.]MM.DD-hh:mm[:ss]
hwclock -w

The MB-SMARC-2 has one SPI interfaces. They can be found on the extension headers and can be tested with a loopback test.

echo -n -e "\x01\x0F" | spi-pipe -d <spi interface> -s 10000000 | hexdump
(e.g. echo -n -e "\x01\x0F" | spi-pipe -d /dev/spidev1.0 -s 10000000 | hexdump)

The file /etc/ssh/sshd_config is used to configure the SSH service. To be able to login with a password as user root change the following lines in the Authentication section

PermitRootLogin prohibit-password

to

PermitRootLogin yes 

and

#PasswordAuthentication yes

to

PasswordAuthentication yes

After altering the SSH configuration, the SSH service must be restarted to apply the new configuration:

systemctl restart sshd.socket

To setup a password for a user, execute the command passwd <username>, e.g. passwd root for the default user root, and set your password. Afterwards execute the login command to login the user with the new password.

The STKa8XxS has one temperature sensor, located on the TQMa8xxS SOM.

Read TQMa8XxS Temperature Sensor

cat /sys/devices/platform/bus@5a000000/5a800000.i2c/i2c-16/16-001b/hwmon/hwmon0/temp1_input

Read CPU internal Temperature Sensor
The i.MX8Xx CPU has an internal TMU that supports two thermal zones, both can be read by the commands below:

Thermal zone0

cat /sys/devices/virtual/thermal/thermal_zone0/temp

Thermal zone1

cat /sys/devices/virtual/thermal/thermal_zone1/temp

With lsusb you can see all connected usb devices. To mount a partition of an usb stick you can excute mount /dev/<partition> <mount dir> (e.g. mount /dev/sdb1 /mnt). This will mount the first partition of sdb to /mnt. To unmount the device execute umount <mount dir> (e.g. umount /mnt).