OLIMEX© 2015
A20-SOM user's manual
memory you will need it to use one of the images available. If you decide to use Debian you would
also need a card. Official Android and Debian images are available at the wiki article for the board.
Recommended items:
- A20-SOM-EVB – reference design of a 2-layer board for A20-SOM which adds VGA, HDMI,
Audio in/out, LCD, 2 MP camera, Gigabit Ethernet, SATA, USB-OTG and 2 USB hosts. The A20-
SOM-EVB board also adapts the 0.05'' step GPIO headers to 0.1'' step headers so you can easily
attach an LCD or UEXT module. Its hardware design is open source and available as Eagle CAD
files, so everyone can modify and tailor it according to the specific needs.
Some of the above-suggested items can be purchased by Olimex, for instance:
USB-SERIAL-CABLE-F
– female USB serial console cable – provides the easiest way of
debugging
A20-SOM-REV-D-DEBIAN-SD
– a tested, class 10 micro SD card suitable for A20-SOM boards
revision C or newer; with latest (by the time of leaving the Olimex facilities) official Debian release
A20-SOM-DEBIAN-SD
– a tested, class 10 micro SD card suitable for A20-SOM boards revision
A and revision B; with latest (by the time of leaving the Olimex facilities) official Debian release
A20-SOM-ANDROID-SD
– a tested, class 10 micro SD card with the latest (by the time of leaving
Olimex facilities) official Android release
2.3 Powering the board
The powering requirements of the A20-SOM are different depending on whether you use it in
stand-alone mode or mounted atop A20-SOM-EVB. The sub-chapters below deal with both
scenarios.
2.3.1 Stand-alone powering
If you use the board in stand-alone mode (e.g. it is neither attached to A20-SOM-EVB nor to any
other board of peripherals) there are fewer options for powering it. Consider that you might need
additional cables or connectors. You have the following options of powering the board:
1. +5V via UART0 header – requires external 5VDC power source
2. 5VEXT via GPIO-2 (5VEXT pin #1; GND pin #2) and GPIO-4 (5VEXT pin #1; GND pin #2) –
requires external 5VDC power source
3. BAT via GPIO-2 (BAT pin #3; GND pin #4) – requires external 4.2VDC battery
4. +5V_OTG_PWR via GPIO-1 (+5V_OTG_PWR pin #5; GND pin #2) – requires external 5VDC
driven by any USB
The default way of powering the board is using external power supply. In that case you would need
to provide 5V DC at the 5VEXT pin of UART0 connector. You would also need to connect the
GND pin of the same connector to the GND line of you supply. The minimum power that your
supply should be able to prove is 2.5W (equivalent of 0.5A of current at 5V of voltage). Note that
there is no standard jack for the powering circuit but you might add own DC power jack.
Do not provide AC voltage to the A20-SOM board! Do not provide more than 5V of voltage
directly to the A20-SOM board! Providing 12V would instantly cause permanent hardware damage!
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