How to use A20 CAN interface with the A20 universal Armbian image for OLinuXino


To use A20 CAN interface you need A20-OLinuXino board and A20-CAN board.

Then you have to install the armbian A20 CAN overlay:


$ sudo armbian-add-overlay <path_to_the_dts_file>


  • connect A20-CAN to your OLinuXino and reboot.

You can see if CAN is available now:

$ ifconfig -a

   can0     Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 
            NOARP MTU:16 Metric:1
            RX packets:0 errors:0 dropped:0 overruns:0 frame:0
            TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
            collisions:0 txqueuelen:10
            RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)


To use CAN interface you can install can-utils and setup the CAN interface:

$ sudo apt-get install can-utils 
$ ip link set can0 down
$ ip link set can0 type can bitrate 100000 triple-sampling on loopback off
$ ip link set can0 up


Now conect A20-CAN to the CAN network two wire interface.

To send a packet over CAN use :

cansend <can_interface> <packet>


For instance:

$ cansend can0 5AA#10.10.10


To sniff for CAN network messages you can use candump :

$ candump can0


Now you can log your car CAN networking messages and interpret them. There is plenty of info on the web about the different CAN messages which are exchanged on car CAN bus.

openSUSE leap 15 on the TERES-I


Torsten Duwe send us note that he is working on openSUSE Leap 15 image for TERES-I which is at same state like the Armbian image.

For these who are interested they can follow the progress here.

TERES-I Open Source Hardware Laptop has new experimental Armbian Mainline Linux image for download


We uploaded few days ago Armbian experimental mainline linux image for TERES-I on our ftp.

There are still few known issues which we work on, but we wanted to upload this experimental image so other people can start playing with.

What is new?

  • eMMC now run x3 times faster which improves the overall user experience.
  • OpenGL with LIMA

Known issues:

  • Automatically turns on upon applying power via the PWR_JACK, we need time to patch mainline uboot
  • No sleep or suspend, WIP.
  • Bluetooth not working out-of-the-box – fixed in Olimex release if you install the package
    with command:

    dpkg -i teres-bluetooth_0.2-1_arm64_armbian.deb

  • Keyboard LEDs not working – fixed in Olimex release – install the package

    with command:

    dpkg -i teres1-ledctrl_0.1-1_armbian_arm64.deb

  • The LCD brightness is low by default (20%) – fixed in Olimex release – to increase it type in the console

    echo 9 > /sys/class/backlight/backlight/brightness

  • no video player acceleration, to be fixed in the next release planned for 22.02.2019


Working with A20 OLinuXino or SOM GPIOs when using new Armbian based A20 universal Linux image


A20 GPIO ports are 32 bit registers listed in alphabetical order PA, PB, PC, PD, PE, PF, PG, PH, PI.

In Armbian GPIO ports are numbered from 0 to 287 corresponding from PA0 to PI31.

The GPIO number is calculating using this formula:

gpioNumber = (Port Letter - 'A') * 32 + pinNumber


For instance GREEN STATUS LED on A20-OLinuXino-LIME2 is connected to port PH2. This will correspond to GPIO number:

('H'-'A' = 7) * 32 + 2 = 226


All GPIO operations in shell should be made as super user. First we have to register the gpio in the Linux Kernel with this command:

sudo echo 226 > /sys/class/gpio/export


to check if we did registered this gpio successfully we use ls command:

sudo ls /sys/class/gpio


If you did everything correctly you will see gpio226 listed.

Then you have to specify what will be this GPIO input or output. This is done with writing “in” or “out” in gpioxx direction directory. In this case we want to drive the STATUS LED so we have to make it output:

sudo echo out > /sys/class/gpio/gpio226/direction


Once we set the GPIO as output we can write 1 or 0 to it’s value and this will make GPIO port to supply 3.3V when 1 is written or 0V when 0 is written.

To switch the LED on we have to write 1:

sudo echo 1 > /sys/class/gpio/gpio226/value


Yay the green LED is now lighting. If we want to switch it off we have to write 0:

sudo echo 0 > /sys/class/gpio/gpio226/value


To read the GPIO state it has to be set as input first with the command:

sudo echo in > /sys/class/gpio/gpioXXX/direction


where XXX is GPIO port number calculated as described above. Then to read the GPIO state you use this command:

sudo cat /sys/class/gpio/gpioXXX/value

the result will be 0 if the GPIO voltage is between 0.0-1.0V and 1 if the voltage is between 2.3-3.3V. If the voltage on the GPIO is between 1.0 and 2.3V the attempt to read will return randomly value 0 or 1.

Be careful when playing with the GPIO ports, some of them are wired to important peripherials like LCD, Ethernet, USB, SATA etc and writing bad values may break the functionality or even damage the board. Test your knowledge on GPIOs which are not connected to anything is best approach.

We are prepare now new version of PyA20 Python module which will add access to GPIO, SPI, I2C, Serial resources of A20 directly from Python code to work with the new universal A20 Armbian Linux image.

EDIT 2019-01-25 14:24:

We got question how fast is the access to the GPIOs via shell. Sure it’s not fast and made just for slow processes like switching on and off relays, or polling status of buttons or sensors which do not change often their state. Running this code below:



Enter inside the file this code:

# the lime2 led is PH2 - 32*(8-1) + 2 = 226

echo 226 > /sys/class/gpio/export
echo out > /sys/class/gpio/gpio226/direction
while [ 1 -eq 1 ]
echo 1 > /sys/class/gpio/gpio226/value
echo 0 > /sys/class/gpio/gpio226/value


Save and exit, then make executable and run

chmod +x


We can see square wave with oscilloscope on PH2 with frequency between 3 and 4 kHz. i.e. pulses with high state 125-150uS and low state 125-150uS.

Shell is slow, if we write same code in C:

#include <stdio.h>
#include <fcntl.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>

#define PH2        226    // (32 * 7) + 2
#define GPIO_PATH  "/sys/class/gpio/gpio226/value"

int main() {
    int ret;
    int fd;

    fd = open(GPIO_PATH, O_RDWR);
    if (fd < 0)
        return errno;

    while(1) {
        ret = write(fd, "1", 1);
        ret = write(fd, "0", 1);

    return 0;


The new code produces square wave with 2.13 us high and low state i.e. approx 235 kHz or about 50 times faster than access via shell.