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.

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.

A20-OLinuXino universal image updated – now supporting our new boards with SPI+eMMC


We just uploaded new A20-OLinuXino universal image at our FTP.

With this image we add support for the new OLinuXino boards with eMMC+SPI.

Few things need some more attention and will be fixed in new image next week: boot from SPI with rootFS on HDD or USB Flash. The new LCD-15.6 eDP display also doesn’t like the new kernel and drivers, but will be fixed too. These are explained in the ISSUES.txt.

The new image also support our new 5″, 7″ and 10″ capacitive touch displays (not on our web for sale yet as still testing) automatically i.e. plug and play and no need to run display script, each time at boot it recognizes the connected display and configure the drivers.

All other peripherals and devices are tested to work with: A20-OLinuXino-LIME, A20-OLinuXino-LIME2, A20-OLinuXino-MICRO, A20-SOM and A20-SOM204.

New univeral A20 image released which works with all our A20 boards and auto detect and configure on boot


We are releasing universal A20 Linux image which will boot and work on all our A20 boards:

The image is based on Armbian with modifications necessary to support OLinuXino specific features.

There are two image releases – Ubuntu Bionic Desktop image which is the recommended image for beginners or when you want to evaluate the board’s hardware fully – it has good HDMI, audio support and Debian Stretch Server image which contains no binary blobs but is headless and has poor video and audio support.

Currently, our latest Ubuntu Bionic A20 image uses kernel 4.19.10, or to be more specific:

root@olinuxino:~# uname -a
Linux olinuxino 4.19.10-sunxi #5.65 SMP Tue Dec 18 14:19:16 EET 2018 armv7l armv7l armv7l GNU/Linu

Our Armbian Ubuntu Bionic image can be downloaded from FTP or Torrent.

Our Armbian Debian Stretch image can be download from FTP or Torrent.

Username is according to Armbian documentation: root and password: 1234

Since we have a large array of A20 boards and numerous variants there is auto-detection enabled in the image. Information about the model of the board is stored in the EEPROM of each A20 board that had been recently manufactured and this information is used by the new images to load the proper configuration. The EEPROM contents are described here.

The images can be used with boards from early revisions which has no EEPROM or has EEPROM with wrong content after one time set up of the EEPROM during in the first u-boot of the new image. If you have trouble booting interrupt u-boot by pressing space and type “olinuxino”. An example configuration for manually setting the EEPROM of A20-OLinuXino-LIME-e16Gs16MB hardware revision K is given at the end of the post.

The new images have support for both legacy resistive and new capacitive/resistive touch displays with auto detection feature (please bear with us they are not released yet on the web as we test them). The newer versions of the displays has suffix -CTS for capacitive touch screen and -RTS for resistive touch screen and are offered in 5″, 7″ and 10″ size with different resolutions. These displays are automatically detected by boot and drivers properly configured for them. If the LCDs are not detected HDMI output is only enabled and the image can be configured one time at first boot manually as described in this wiki article.

Please note that mainline Kernel now do not support NAND Flash, so if you wish to boot from the flash memory, consider either using the legacy 3.4.xx images which are still available or switch to A20 boards with eMMC. The eMMC boot is supported via armbian-config (nand-sata-install). Due to lack of reliable eMMC 5.X support by Allwonner boot0 and for future compatibility we are adding 16MB SPI flash for all A20 boards with eMMC, this way the board first boots from the SPI then continue to eMMC with properly set configuration. Allwinner Boot0 can’t handle correctly eMMC 5.X and sometime boot sometimes do not boot, as this is binary blob inside SOC there is nothing we can do than to use SPI boot to fix eMMC boot parameters.

Build instructions for the new images can be found here.

An example configuration for manually setting the EEPROM of A20-OLinuXino-LIME-e16GB hardware revision K is given below:

=> olinuxino 
olinuxino - OLinuXino board configurator

olinuxino config info - Print current configuration: ID, serial, ram, storage, grade...
olinuxino config list - Print supported boards and their IDs
olinuxino config erase - Erase currently stored configuration
olinuxino config write [id] [revision] [serial] [mac]
[id] - Specific board ID
[revision] - Board revision: C, D1, etc...
[serial] - New serial number for the board
[mac] - New MAC address for the board
Format can be:
olinuxino monitor list - Print supported video outputs
olinuxino monitor set - Set specific LCD

=> olinuxino config list

Supported boards:
A20-OLinuXino-LIME - 7739 
A20-OLinuXino-LIME-n4GB - 7743 
A20-OLinuXino-LIME-n8GB - 8934 
A20-OLinuXino-LIME-s16MB - 9076 
T2-OLinuXino-LIME-IND - 9211 
T2-OLinuXino-LIME-s16MB-IND - 9215 
T2-OLinuXino-LIME-e4GB-IND - 9219 
A20-OLinuXino-LIME2 - 7701 
A20-OLinuXino-LIME2-e4GB - 8340 
A20-OLinuXino-LIME2-e16GB - 9166 
A20-OLinuXino-LIME2-n4GB - 7624 
A20-OLinuXino-LIME2-n8GB - 8910 
A20-OLinuXino-LIME2-s16MB - 8946 
A20-OLinuXino-LIME2-e16Gs16M - 9604 
A20-OLinuXino-LIME2-e4Gs16M - 9613 
T2-OLinuXino-LIME2-IND - 9239 
T2-OLinuXino-LIME2-s16MB-IND - 9247 
T2-OLinuXino-LIME2-e4GB-IND - 9243 
A20-OLinuXino-MICRO - 4614 
A20-OLinuXino-MICRO-e4GB - 8832 
A20-OLinuXino-MICRO-e16GB - 9042 
A20-OLinuXino-MICRO-e4GB-IND - 8661 
A20-OLinuXino-MICRO-IND - 8828 
A20-OLinuXino-MICRO-n4GB - 4615 
A20-OLinuXino-MICRO-n8GB - 8918 
A20-OLinuXino-MICRO-s16MB - 9231 
T2-OLinuXino-MICRO-IND - 9223 
T2-OLinuXino-MICRO-s16MB-IND - 9235 
T2-OLinuXino-MICRO-e4GB-IND - 9227 
A20-SOM-n4GB - 4673 
A20-SOM - 7664 
A20-SOM-IND - 8849 
A20-SOM-n8GB - 8922 
A20-SOM-e16GB - 9155 
A20-SOM-e16GB-IND - 9148 
T2-SOM-IND - 9259 
A20-SOM204-1G - 8991 
A20-SOM204-1Gs16Me16G-MC - 8958

=> olinuxino config write 9166 k

Erasing EEPROM configuration...
Writting EEPROM configuration...
Writting MMC configuration...

=> saveenv

Saving Environment to EXT4... Recovery required
update journal finished

=> reset

OLinuXino EEPROM content – one step ahead to single Linux image for all A20 boards


We are struggling for some time now to make one single image which to work on all A20 boards we have.

Our problem is that we have more than 20 different A20 boards/revisions/ etc and every time we have to add or improve something we have to generate and test enormous amount of images.

It’s not so easy task as this image should run on different boards with differnt memory speed etc settings, different ports connections etc.

To achieve one single image which to boot to all A20 boards our first step is to add some content in the EEPROM which all OLinuXino has.

The EEPROM now contain this info: Header, ID, Revision, Serial number, Configuration, Reserved area for future (MAC etc), Checkcum.

The new image we work on now (based on Armbian with mainline kernel) will automatically recognize the board from the EEPROM content and run.

What will happen if no valid EEPROM content is read (i.e. old boards), there is tool which to be used to write EEPROM content based on board revision.

We are going to release this image soon.