- A20 dual core Cortex-A7 processor
- 1GB DDR3 memory
- AXP209 PMU IC
- MicroSD card
- UART console
- 4GB NAND Flash
- Status LEDs
- RESET, RECOVERY buttons
- 6 connectors x 40 pin 0.05" step
Official Images from OLIMEX
Note that only the microSD connector is suitable for booting the desired operating system, the SD-MMC connector is not suitable for booting since it is not a part of the boot sequence (refer to A20 datasheet).
The Debian Linux image is 4GB and the file system can be extended to suit a bigger card. Use the following three commands to execute a script that would use all the free space of your card:
resize_sd.sh /dev/mmcblk0 2
The official Debian images are suitable only for microSD card. Information on booting Debian from the NAND might be found at the forum.
Download methods and locations might be found below! Please note that there are different images for different board revisions, due to a hardware change.
Newest official release (recommended):
Torrent of Debian release 3 suitable for boards with hardware revision C or newer (boards with printed board revision C; board revision D; etc). The image would not work with boards older than board revision C: A20-SOM Debian with kernel 3.4.90+ release 3, for boards revisions C and D
Torrent of Debian release 3 suitable for boards with hardware revision up to revision B (boards with printed board revision A or board revision B): A20-SOM Debian with kernel 3.4.90+ release 3, for boards up to revision B
Image description and typical interfacing: description and basic usage of different peripherals at at the GitHub page
Image build instructions and required files for the latest Debian images: build instructions and required files at the GitHub page
Older official releases (not recommended):
Torrent of Debian release 2: A20-SOM Debian with kernel 3.4.90+ release 2
Direct download of Debian release 1: A20-SOM Debian with kernel 3.4.79+ release 1
Instructions for preparing the Debian image: Debian with Kernel 3.4.79+ build instructions
The list of all installed packages is located in A20-SOM-installed_packages.txt file inside the image.
The latest image includes installations for the following:
- Linux Kernel 3.4.90+
- LXDE desktop environment
- Mplayer CLI
- Midori browser
- GCC 4.6
- GPIO support
- Python 2.7
Tested board peripherals with this image:
- GPIOs - they are located in /sys/class/gpio directory. Note that first you have to export GPIOs. For example:
# for i in `seq 1 1 230`; do echo $i > /sys/class/gpio/export; done
will export all available GPIOs
# echo out > /sys/class/gpio/gpioXX_pxx/direction
will make the port output
# echo 1 > /sys/class/gpio/gpioXX_pXX/value
will make the port output in logical 1
- LCD - 4.3(480x272), 7(800x480), 10(1024x600), 15(1366x768)
- SATA - with power on/off control
- HDMI - the default HDMI resolution is 720p60(720x1280 - 60 Hz)
- Touch_screen support - you need calibrate LCD before using touch screen and in certain cases you would also need to select the proper video configuration. Note that if you want to use touch screen in X environment then you have to calibrate it like olimex user, not like root user because X environment is started like olimex user. For example type:
calibrate the touch screen and reboot the board
in order to test MOD-USB3G module you have to place SIM card(without pin code) in module and
connect it to USB host connector change settings in /etc/wvdial.conf file according to your
mobile operator and type:
# wvdial 3gconnect
- micro_SD_card - linux starts from micro_SD card
- second_SD_card - with card present capability
- ETHERNET - 100Mb/1000Mb
- MIC IN
MIC_IC can be tested with:
# arecord -f dat -r 60000 -D hw:0,0 -d 5 test.wav
this command will record 5 sec audio stream from microphone in test.wav file
Headphones output can be tested with:
# aplay -D hw:0,0 test.wav
this command will play the audio stream from test.wav file
- NAND support - /dev/nandX
- I2C2(100KHz) - /dev/i2c-2
- I2C1(100KHz) - /dev/i2c-1
- UART6 - /dev/ttyS1
- UART7 - /dev/ttyS2
- SPI1 - /dev/spidev1.0
- SPI2 - /dev/spidev2.0
there is a simple test for SPI2 in /opt/spidev directory.
# ls /opt/spidev
in folder max6675/ there is example related with MOD- TC(link to product) -
temperature sensor that you have to connect to UEXT1 connector
# cd max6675
the last command will read temperature from MOD-TC thermocouple in folder MOD-SMB380 there is
example related with MOD-SMB380(link to product link to product page)3-AXIS ACCELEROMETER
BOARD that you have to connect to UEXT1 connector
# cd MOD-SMB380
the last command will read temperature and 3-asix accelerometer values
BUTTONs - we use evtest package for testing. For example:
then enter 2 for event number and now you can press the BUTTONs and you should see the result on terminal window
Torrents of official Android releases are below. Please read description of the image carefully.
Torrent of Android 4.2.2 release 1 for NAND memory (with HDMI and 800x480 support): A20-SOM Android for NAND with HDMI and 7 inch display support
Torrent of Android 4.2.2 release 1 for microSD card (with HDMI and 800x480 support): A20-SOM Android for microSD card with HDMI and 7 inch display support
Direct download locations of official Android releases are below. In case the daily limit of the download locations had been reached, please use the torrents above. Please read description of the image carefully.
Direct download of Android release 1 for microSD card microSD card image for Android 4.2.2 with 7″ LCD 800×480 pixels
A20 User Manual
A20 Users manual
A20-SOM and A20-SOM-4GB basic dimensions in mils: click
A20-SOM-EVB basic dimension in mils: click
Power supply and consumption
A20-SOM typically consumes between 0.20A and 0.25A when connected to a 5V
voltage source (provided at pins GND and 5VEXT).
During heavy load of the processor the consumption might raise up to 0.35A
(tested with 'top d0').
The current consumed might have peaks as high as 0.50A @ 5V during start-up when
different modules are initialized.
Make sure your supply is capable of providing at least half an ampere of
current at 5V of voltage.
The consumption of the combination A20-SOM + A20-SOM-EVB is betwen 0.10A and 0.15A when the A20-SOM-EVB is connected to a 12V voltage source (provided at the board's PWR jack).
During heavy load of the processor the consumption might raise up to 0.20A @ 12V
(tested with 'top d0').
The current consumed might have peaks as high as 0.25A @ 12V during start-up when
different modules are initialized.
A20-SOM is considered commercial, proprietary design. The board file is not available to the customer. A pdf extracted from the original schematic is available at GitHub: A20-SOM schematics
KiCAD files of the connectors of A20-SOM/A20-SOM-EVB that are perfect as a template for own design can be found here: KiCAD templates A20-SOM
A20-SOM-EVB is considered Open Source Hardware, Eagle CAD files are available here A20-SOM-EVB sources
The CAD product used to design OLinuXino is Eagle and you can download evaluation free version from their web site. The evaluation version allows you to inspect the schematic and the board file sources.
How to correctly power off OLinuXino running from NAND Flash
In this Blog post we explain what are the problems. This is common problem for all computers running OS. Here you can read more about MLC NAND Flash and Linux file system.
How to generate boot-able SD-card Debian Linux image for A20-SOM?
Build instructions and required files for the latest Debian images: instructions and files at the GitHub page
Follow our blog post with step by step instructions Note that Linux-Sunxi Kernel is a work-in-progress, this means you can try the current stage/sunxi-3.4 branch but if something is broken and doesn't work just revert to the git tags we give in the blog and they should work for sure
Sunxi u-boot loader - the linux-sunxi git page contains a lot of sources for all Olimex Allwinner boards.
How to download new Android image to the NAND memory of my A20 board?
To repair the image on the NAND re-upload it following these steps:
1. Install and run PhoenixSuit (can be found here: google drive location).
2. Download and extract the latest official image from the Android section of the wiki: A20-SOM article. Make sure that the download link you visit clearly indicates that the image is suitable for the NAND memory since there are images suitable for microSD card also. The images suitable for the microSD memory and those suitable for microSD card are different. However, the upload method is almost identical – using PhoenixSuit.
3. Go to firmware tab of the program and point to the already downloaded and extracted Android image.
4. Disconnect the power supply and USB cable from the A20 board.
5. Press and hold RECOVERY button, apply power supply (the requirement various depending on whether you use the board stand-alone or on top of A20-SOM-EVB), release RECOVERY button.
6. Connect USB cable to the mini USB connector.
7. You will be asked for drivers for the bootloader. Navigate to the folder where you extracted the PhoenixSuit and install the drivers from the respective executable (or manually point the installer to the drivers folder in the PhoenixSuit installation path).
8. PhoenixSuit will detect the board and would ask whether you wish to also of writing the image. Choose method of writing the image and confirm your wish to write the image.
9. Wait till upgrade succeeds
Note that it is not recommended to have your mini USB connected to an external USB hub. This might cause delays and might distort the signal levels. Always test with the USB connected straight to the USB ports of your computer.
How do I write the official Android image to a micro SD card for my A20 board?
A: First download one of the official Android images, which might be found in the Android section above.
Make sure that the download link you visit clearly indicates that the image is suitable for the microSD card since there are images suitable for NAND memory also. The images suitable for the microSD memory and those suitable for NAND card are different. However, the upload method is almost identical – using PhoenixSuit.
There are two types of Android images for microSD card that we usually provide and each of them has to be downloaded to a microSD card using a different method. The image provided for microSD card is either the native Android image that can be downloaded to the card via a software tool like PhoenixSuit (through the board) or an image taken from an already prepared microSD card that requires to simply write the image (through a microSD card reader).
It is more likely that you have an Android image that requires a simple copy to a card. If that is the case you can follow the exact steps as for Linux (e.g. using "Win32 Disk Imager" or "dd" command).
In order to prepare a microSD card with a native Android you will need a software tool called PhoenixSuit and then:
• Install and run PhoenixSuit (can be found here: download from google drive)
2. Go to the firmware tab of the program and point to a valid Android image (note that the images on Google drive are compressed and you have to extract the archives to .img files to be able write them with PhoenixSuit)
3. Disconnect the power supply and USB cable from the A20 board. Put an SD card in micro SD holder. We recommend 4GB class 10 card.
4. Press and hold RECOVERY button, apply power supply (the requirement various depending on whether you use the board stand-alone or on top of A20-SOM-EVB), release RECOVERY button.
5. Connect USB cable to the mini USB connector.
6. You will be asked for drivers for the boot-loader. Navigate to the folder where you extracted the PhoenixSuit and install the drivers from the respective executables (or manually point the installer to the drivers folder in the PhoenixSuit installation path).
7. PhoenixSuit will detect the board and would ask for the method of writing the image. Choose method of writing the image and confirm your wish to write the image.
8. Wait till upgrade succeeds
Note that it is not recommended to have your mini USB connected to an external USB hub. This
might cause delays and might distort the signal levels. Always test with the USB connected straight to the USB ports of your computer.
Important: When Android runs for very first time it takes several minutes to initialize all files and buffers please do not cut the power supply during this process! Also when fresh image is installed fast boot may be disabled, which means that when you apply power supply after few seconds Android will go in sleep mode and you have to press POWER button to start it, you can change to fast boot when you power off there is dialog box asking you if you want next boot to be fast boot, you have to check this box before you power off. Also note that you must do touch screen calibration when you run Android for very first time which might require a mouse.
How do I write the Linux image to a micro SD card to use with my A20 board?
To write a Linux image to an SD card under Windows we use Win32 Disk Imager):
- Download Win32 Disk Imager Win32 Disk Imager
- Insert card
- Start program
- Select file
- Click "write"
To write a Linux image to an SD card under Linux:
For instance you have an image with the file name of "debian_2g.img". It would be downloaded to the SD card connected to a Linux machine using one of the following commands:
- # dd bs=4M oflag=sync if=debian_2g.img of=/dev/sdX
- # cp debian_2g.img /dev/sdX
where X is the uSD card.
I don't have neither serial cable, nor HDMI monitor. I also can't access the local Ethernet network. Can I somehow access the board anyway?
The latest official Debian Linux image allows the use the USB_OTG connector for SSH connection without the need of a LAN cable or a serial cable. You can use a mini USB cable connected between your host PC and the on-board mini USB connector. For connection convenience there is a DHCP server running specifically for USB0 interface. The DHCP server should give IP address to the new USB0 interface of your host PC so you can make SSH connection from your PC to the default board IP address of the USB0 interface – 192.168.2.1.
You can connect to the board using a mini USB cable and an SSH client (if you use Windows you might use "puTTY", for example) at address 192.168.2.1.
For Windows operating system - upon connection, the board should show up in "Windows Device Manager" as "RNDIS Ethernet Gadget". You might be asked to install a driver. The drivers can be found online as "RNDIS driver" (Remote Network Driver Interface Specification). The drivers are provided by Microsoft and they should be available for every Windows distribution - refer to the respective files and articles provided by Microsoft on how to install the required drivers.
How to change HDMI, VGA and LCD resolutions in the official Debian image?
The default SD card setup is made with settings for HDMI 720p/60Hz. If you want to change to some other LCD, VGA or HDMI resolution then you have to start change_display.sh script file in /root directory.
and press "Enter".
Then choose the resolution and the interface(LCD, HDMI or VGA). Note that the selection of a specific resolution is done by navigating with the arrow keys and pressing "space" button. Make sure the asterisk marks your selection properly.
The supported resolutions are:
- 1. 4.3" (480x272)
- 2. 7" (800x480)
- 3. 10" (1024x600)
- 4. 15.6" (1366x768)
Important: initially the boards are calibrated for a specific display. If you re-write the image (no matter whether the SD card or the NAND memory) you would need to use a mouse to calibrate the display initially. It might be impossible to calibrate it via touching the display.
- 0. 480i
- 1. 576i
- 2. 480p
- 3. 576p
- 4. 720p50
- 5. 720p60
- 6. 1080i50
- 7. 1080i60
- 8. 1080p24
- 9. 1080p50
- 10. 1080p60
- 11. pal
- 14. ntsc
For VGA: (note that the VGA signals are routed to custom 6 pin connector and you need from adapter to standard VGA connector)
- 0. 1680x1050
- 1. 1440x900
- 2. 1360x768
- 3. 1280x1024
- 4. 1024x768
- 5. 800x600
- 6. 640x480
- 7. 1920x1080
- 8. 1280x720
How to edit board configurations and definitions in the official Debian Linux?
Do you want a custom video resolution output? Do you need a different port definition? Do you need to change the hardware defitions of the board?
You would need to edit the board's script.bin/script.fex file. How to do it is described in a separate article: How_to_edit_board_configurations_and_definitions_in_the_official_Debian_Linux.
How to generate Arch Linux image?
Recent forum post by user progmetalbg here: at Olimex forums
Older step by step instructions on how to build Arch Linux image for another A20 board
How to detect and enable the Ethernet controller (if it is disabled by default)?
Note: in the previous Debian releases the Ethernet was auto-detected and initialized during boot BUT this was causing big delays in the start-up of the board if you didn't want to use Ethernet or if there wasn't Ethernet cable connected.
You can enable it by following these two steps:
1. To check under what name the LAN is associated write "ifconfig –a"
2. If, for example, it is under eth0 name, then write: "dhclient eth0"
This should enable the Ethernet and then SSH would also be available.
How to install Android on SD-card?
Blog post about it
How to access UART, I2C, GPIOs under Android?
Use our Open Source OLinuXino A20-TOOLS
How to control PWM under Linux?
There is an article here: how to add pwm
How to build the Android 4.2.2 image for A20-OLinuXino-MICRO?
First you need to Download the A20 SDK2.0 Linux Kernel 3.4
Second you need to configure your environment read the instructions here
Then Build the kernel, kernel modules and u-boot
When done, continue with Bulding the android image:
tar zxfv olinuxino-a20.tgz
lunch #select olinuxino-a20_eng
Dave from Axon instruments wrote more detailed blog post about how he generates the Android image]
How to build Debian Linux image for A20-OLinuXino-MICRO?
Build instructions and required files for the latest Debian images: instructions and files at the GitHub page
Older image building instructions: at Google Drive; Kernel 3.4.79+