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OLIMEX A20-SOM [7/41] Board variants
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OLIMEX© 2015 A20-SOM user's manual
1.4 Board variants
There are two major board variants named: A20-SOM and A20-SOM-4GB. The 4GB version has
built-in NAND memory that allows the storage of an operating system without the need of a SD
card (at the moment of writing this document Olimex provides only Android OS for the NAND).
The 4GB version comes with already programmed and ready-to-use Android OS image.
The other Olimex board with close characteristics is A13-SOM board. It is much cheaper and
smaller. It heats less and consumes less power. However, it features a generation older processor
and lesser amount of RAM memory, making it less desirable for heavy computations (for instance,
high resolution video decoding and encoding).
Other SOM boards that might be compared to functionality are the and quad-core ARM Cortex-A9
RK3188-SOM and the BeagleBone-inspired AM3352-SOM.
1.5 Board versions used in the manual
The documents follows the hardware layout of A20-SOM board revision D. There might be revision
B pictures left over.
Note that major changes in the hardware design were introduced in A20-SOM board revision C.
Boards from the initial couple of revisions have visible differences compared to boards from
revisions C and on. Yet, the two major functional differences are the improved memory clock speed
(480MHz compared to the initial 384MHz) and the presence of the additional GPIO-6 connector. It
is important to notice that different board revision might use different Debian images!
A20-SOM-EVB revision C peripheral board was used while writing this document.
Different board revisions might have different features or settings. It is possible that parts of this
document do not apply to all board revisions.
1.6 Document organization
Each section in this document covers a separate topic, organized as follows:
– Chapter 1 is an overview of the board usage and features
– Chapter 2 provides a guide for quickly setting up the board and software notes
– Chapter 3 contains the general board diagram and layout
– Chapter 4 describes the component that is the heart of the board: the A20 – Allwinner
processor
– Chapter 5 is an explanation of the control circuitry associated with the microcontroller
– Chapter 6 covers the connector pinout, peripherals and jumper description
– Chapter 7 provides the schematics and the dimensions of the board
– Chapter 8 contains the revision history, useful links and support information
Page 7 of 41
Содержание
- A20 som and a20 som 4gb 1
- System on module boards capable of linux and android boot 1
- User s manual 1
- Disclaimer 2
- There is no warranty for the design materials and the components used to create a20 som a20 som 4gb and a20 som evb they are considered suitable only for a20 som a20 som 4gb and a20 som evb respectively 2
- Chapter 1 overview 5 3
- Chapter 2 setting up the a20 som board 8 3
- Chapter 3 board description 18 3
- Chapter 4 the allwinner a20 microcontroller 19 3
- Chapter 5 control circuity 21 3
- Chapter 6 connectors and pinout 22 3
- Disclaimer 2 3
- Table of contents 3
- Chapter 7 schematics 32 4
- Chapter 8 revision history and support 33 4
- Chapter 1 overview 5
- Introduction to som system on a module 5
- Introduction to the chapter 5
- Features of a20 som 6
- Target market of the board 6
- Board variants 7
- Board versions used in the manual 7
- Document organization 7
- Chapter 2 setting up the a20 som board 8
- Electrostatic and electrical polarity warnings 8
- Introduction to the chapter 8
- Requirements 8
- Powering the board 9
- Stand alone powering 9
- Button functions 10
- Mounted powering 10
- Interacting with the board 11
- Changing the default image resolution 12
- Expanding the debian file system space 12
- Cable 40 40 10cm 10cm long cable suitable for 0 5 step connectors product page 15
- Cable idc40 15cm 15cm long cable suitable for 0 step connectors product page 15
- Connecting and calibrating a display 15
- Newer displays made by olimex have both 0 and 0 5 step connectors going for an lcd output you would also need need a compatible cable to attach the display to the board the cable is sold separately 15
- One of the ways to interact with the board is via an external display with or without touchscreen component however there is only a 40 pin female connector lcd_con with a 0 5 step 15
- The cable used for connection depends on the specific board you are using and more specifically it depends on the pitch of the lcd connector of the board we have two cables both 40 pins ones but one for the bigger pitch 0 and the other for the smaller one 0 5 each of the displays listed in the table above has two connectors suitable for both cables 15
- The displays recommended for the board at the moment of writing might be found in the table below 15
- The displays whose names contain ts include a resistive touch screen component 15
- The typical a20 som user would not need to edit the files however 15
- Unlike other olimex allwinner boards the a20 som lacks a row of pins that allows the user to connect a display out of the box the board s lcd_con connector is female and has a smaller 0 5 step this means that if you use a display made by olimex you would need additional 2 20 male male 0 5 header to convert the female connector to male the 0 5 headers are somehow hard to find so we sell them here 0 5 step connectors 15
- Android calibration 16
- Debian calibration 16
- Software support 17
- Chapter 3 board description 18
- Introduction to the chapter 18
- Layout top view 18
- Chapter 4 the allwinner a20 microcontroller 19
- Introduction to the chapter 19
- The processor 19
- Block diagram 20
- Chapter 5 control circuity 21
- Clocks 21
- Introduction to the chapter 21
- Power supply circuit 21
- Chapter 6 connectors and pinout 22
- Communication with a20 som in linux 22
- Introduction to the chapter 22
- Uart0 pins 22
- Microsd card connector 23
- Sd mmc slot 23
- Below you would find tables with the signal at each pin to understand better what each processor pin does it might be a good idea to refer to the datasheet of the a20 processor the schematic of the board of peripherals a20 som evb might also help you identify the main function of the pins 24
- Gpio connectors 24
- Important boards revisions prior to revision c have only 5 x gpio connectors the 14 pin gpio 6 connector is not available 24
- Important the connectors are very fragile if you attempt to disconnect the board by pulling only one side out it might break furthermore you might bend the board s pins use pliers or other suitable object to disconnect the connectors carefully 24
- More info about the power supply can be found in chapter 5 of this manual 24
- Power pins for external power supply 24
- The recommended way of powering the board are the power pins located on the uart0 connector they are suitable for 5v dc external power supply unit the required current may vary depending on the peripherals connected to the board the power supply should be capable of providing at least 0 a of current 24
- The signal names are printed under the pins make sure to inspect the names before connecting the supply 24
- The uart0 connector features also the pins suitable for serial communication with the board for the powering we are only interested in pins 5vext and the pin next to it gnd 24
- There are 6 gpio connectors located on the top side of a20 som they ease the access to processors pins these connectors except for gpio 6 also provide a way to mount the board to a board with peripherals 24
- To keep the form factor as small as possible the gpio connectors have 0 5 step 24
- Gpio 1 general purpose input output 40pin connector 25
- Olimex sells additional and replacement male and female 0 5 50 mil step connectors we also have a suitable cable named cable 40 40 10cm 25
- The only power line at the gpio connectors that might be used as input is the one named 5vext the rest of the power signals are outputs and it would be incorrect to try to power the board from there 25
- Gpio 2 general purpose input output 40pin connector 26
- Gpio 3 general purpose input output 40pin connector 27
- Gpio 4 general purpose input output 40pin connector 28
- Gpio 5 general purpose input output 40pin connector 29
- Gpio 6 general purpose input output 10pin connector 29
- It has some points that might be used as test pads also couple of signals that might be used to debug the power supply 29
- This connector was added in hardware board revision c it is missing in board revisions a and b 29
- Full list of recommended displays for the board might be found in chapter 2 connecting and calibrating a display 30
- Important you would probably need an additional adapter board and two different 40pin ribbon cables to connect an olimex display and the lcd_con the evaluation board rk3188 som evb provides a 0 step lcd connector which eases the hardware interfacing between the board and the display 30
- Lcd_con 40pin connector 30
- Note that the smallest display 4 480 272 is not suitable for the official android images we provide 30
- The lcd connector is suitable but not plug and play due to the different pin step for a number of olimex displays and touchscreen panels with different native resolution the smallest available is the 4 one called lcd olinuxino 4 ts with native screen resolution of 480 272 through the 7 one named lcd olinuxino 7ts with 800 480 to the 1024 600 10 lcd olinuxino 10ts 30
- The lcd_con pins are led out on a separate 40pin connecter for the ease of connecting an lcd the step of the connector of a20 som is still 0 we have tested the ability of the board to interact with such a display they allow the user to attach additional hardware check readings or perform hardware debug 30
- Additional hardware components 31
- Chgled lights when charging a battery connected to the li po battery connector 31
- Gb 1 32gb 4096 m x 8 bit nand flash only available on the 4gb version of the board the exact memory used in the board revision mentioned is hynix h27ubg8t2a 31
- Gb 2 4gb 256 m x 16 bit ddr3 sdram the exact memory used currently is samsung k4b4g1646d bck0 the memory clock in board revisions a and b of a20 som was 384mhz the memory clock in hardware revisions c d and newer ones is improved to 480mhz 31
- Jumper description 31
- Please note that two jumpers on the board are smt type if you feel insecure of your soldering cutting technique it is better not to try to adjust the jumpers since it is possible to damage the board 31
- Pwr_led turns on upon powering the board 31
- Reset button used to reset the board power button used to power up the board recovery button used to wake up the board from power down state 31
- The components below are mounted on the a20 som but are not discussed above they are listed here for completeness 31
- The ddr3 memory part name in the schematic might be outdated we have used a number of different but fully compatible ddr3 memories due to supply unavailability it is always recommended to check the exact memory name printed on the component itself 31
- Chapter 7 schematics 32
- Eagle schematic 32
- Introduction to the chapter 32
- Physical dimensions 32
- Chapter 8 revision history and support 33
- Document revision 33
- In this chapter you will find the current and the previous version of the document you are reading also the web page for your device is listed be sure to check it after a purchase for the latest available updates and examples 33
- Introduction to the chapter 33
- Board revision 34
- Remember to check the schematics and the board design files to compare the differences 34
- Useful web links and purchase codes 35
- Frequently asked questions 37
- For product support hardware information and error reports mail to support olimex com all document or hardware feedback is welcome note that we are primarily a hardware company and our software support is limited please consider reading the paragraph below about the warranty of olimex products 41
- Olimex 2015 a20 som user s manual 41
- Page 41 of 41 41
- Product support 41
- The full text might be found at https www olimex com wiki gtc warranty for future reference 41
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