Embedded module TQMa8Xx4 - YOCTO Linux BSP documentation

Starterkit Interfaces and Functions

Audio

Audio Connector Overview

Connector	Function
X8	Microphone
X9	Line In
X10	Line Out

The microphone is not supported with the current BSP version.

Audio Connector Location

$\|$

Play Audio on

A simple test sound can be played with the commandline tool speaker-test.
Headphones or active speakers have to be connected to X10 on .

speaker-test --channels 2 --test wav -D sysdefault:CARD=tqtlv320aic32x

You can also play your own audio files using aplay

aplay <file>

e.g.

aplay test.wav

Please notice that no audio test files are available in the default image.

Record Audio via Line-In on

arecord -f cd test.wav

The audio settings can be altered using amixer or alsamixer

“|mb_name=“MBa8Xx”}}

Buttons

There are two GPIO buttons on the MBa8Xx. They are bound to the gpio-keys driver, and can be tested with the evtest tool.

GPIO Button Overview

Reference	Button

GPIO Button Location

$\|$

The buttons are available in the sysfs via the device and can be tested with the evtest tool.

“|button_device=”/dev/input/event1”|button_test=“evtest /dev/input/event1”}}

CAN

The MBa8Xx provides the CAN interfaces CAN0 and CAN1.

CAN configuration

DIP switches SW1 and SW2 are used to configure the CAN interfaces CAN0 and CAN1.

Function	SWx-1	SWx-2
CAN-Bus not terminated	OFF	OFF
not defined (illegal state)	OFF	ON
not defined (illegal state)	ON	OFF
CAN-Bus terminated with 120 Ohm	ON	ON

CAN Loopback

“{{ :en:arm:tqma8xx:linux:yocto:tqma8xx_can_loopback.png?nolink&400 |

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

“}}

CPU

The STKa8Xx4 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.

Governor	description
performance	Run the CPU at the maximum frequency.
powersave	Run the CPU at the minimum frequency.
userspace	Run the CPU at user specified frequencies.
ondemand	Scales the frequency dynamically according to current load. Jumps to the highest frequency and then possibly back off as the idle time increases.
conservative	Scales the frequency dynamically according to current load. Scales the frequency more gradually than ondemand.
schedutil	Scheduler-driven CPU frequency selection

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

Set ammount of CPU Cores permanently

It is possible to limit the maximium amount of cores with the the maxcpus= parameter in the kernel command line. To add the new parameter a new U-boot variable addcpu has to be created.

setenv addcpu maxcpus=${cpu_num}

The amount of cores is set by the cpu_num variable, for example if cpu num is set to 2 only two cores will be started.

setenv cpu_num 2

Ethernet

The STKa8Xx4 Starterkit provides two Gigabit Ethernet interfaces.

U-Boot

In U-Boot eth0 is configured as default interface. The IP configuration can be done statically or by a DHCP server in the network.

IP configuration via DHCP

For a configuration via a DHCP server, use the dhcp command in U-Boot.

Static IP configuration For a static IP configuration the following, U-Boot environment variables must be set:

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

Linux

Both Ethernet interfaces are activated and configured by systemd-network. The configuration files for the interfaces are located in /lib/systemd/network/ these configuration files can be altered to customize the default interface configuration. A documentation of the configuration files can be found here.

For a temporary static configuration the ip command can be used, below some useful ip commands are listed:

Activate a specific interface
e.g. eth0

ip link set eth0 up

Disable a specific interace
e.g. eth0

ip link set eth0 down

Show ip address for a specific interface
e.g. eth0

ip addr show eth0

Show statistic for a specific interface
e.g. eth0

 
ip -s link show eth0

Set ip address for a specific interface
e.g. eth0

ip addr add 192.168.1.100/24 dev eth0

Show statistic of all interfaces

ip -s link

Set default gateway for a specific interfaces
e.g. set gateway ip 192.168.1.1 for eth0

ip route add default via 192.168.1.1 dev eth0

If a DHCP server is available in the network environment the ip configuration can be received from it. To do so execute the udhcpc command, by default eth0 is used.
To configure another interface via dhcp the parameter -i followed by the interface name e.g. eth1 must be given.
e.g. eth1

udhcpc -i eth1

GPU

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

glmark2-es2-wayland --fullscreen

I2C

An overview of the onboard i2c devices is available here

U-Boot

Select i2c bus device

i2c dev 1

Show all devices connected to the i2c bus currently selected:

i2c probe

Linux

Detect all devices connected to a i2c bus:

i2cdetect 16

LVDS

TQ offers an optional LVDS Display kit for the STKa8Xx4. 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: With MBa8Xx only one control interface for backlight is available (X22).

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

Interrupt boot process in U-boot
Set U-Boot environment variable fdt_file with the command setenv fdt_file <device tree> (e.g. setenv fdt_file imx8qxp-mba8xx-lvds0-tm070jvhg33.dtb)
Save the envrionment by executing the saveenv command

RTC

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

SPI

The MBa8Xx has three SPI interfaces. They can be found on the extension headers and can be tested with a loopback test.

SPI Overview

Interface	linux filesystem

Loopback Test SPI Interface

For the loopback test you need a bridge between SPI_MOSI and SPI_MISO:

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)

SSH Connection

Please keep in mind that the following instructions focus on simplicity, not on security.

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

PermitRootLogin yes

and

#PasswordAuthentication yes

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.

Temperature Sensors

@temp_description@ @temp_sensors@

USB

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).

User LED

The MBa8Xx has two user controllable LEDs, the behavior of these LEDs can be selected by several triggers.

User LED Overview

Reference	LED name	color	linux filesystem

User LED Location

“{{ :en:arm:tqma8xx:linux:yocto:mba8xx_user_led.png?nolink&300 |

The user LED's are located in .
To change the behaviour a specific LED, the value in the file trigger must be overwritten.

The following values are valid:

For example set the trigger of to heartbeat

echo heartbeat >

“|userled_location=”/sys/devices/platform/gpio-leds/leds/“|led_example=“ledb”|userled_example=”/sys/class/leds/ledb/trigger”}}