![OLIMEX A20-SOM [22/41] Chapter 6 connectors and pinout](/img/pdf.png)
OLIMEX A20-SOM [22/41] Chapter 6 connectors and pinout
![OLIMEX A20-SOM [22/41] Chapter 6 connectors and pinout](/views2/1659506/page22/bg16.png)
OLIMEX© 2015 A20-SOM user's manual
CHAPTER 6: CONNECTORS AND PINOUT
6. Introduction to the chapter
In this chapter are presented the connectors that can be found on the board all together with their
pinout and notes about them. Jumpers functions are described. Notes and info on specific
peripherals are presented. Notes regarding the interfaces are given.
6.1 Communication with A20-SOM in Linux
The direct access method to the Linux command interface is via the serial interface. You would
need to use the pins of the UART0 and then use your favorite terminal program (puTTy, minicom,
picocom, teraterm, etc) to access the command line interface of the debian the data/send commands.
You can use USB-SERIAL-CABLE-F with the UART0 interface that allows you to connect to a
personal computer with a free USB port.
If you decide to make your own cable you would need to consider that the levels at board's UART0
are in CMOS level (3.3V) and you would need a convertor to bring them to the TTL level of your
computer or cable! That is true for the RX and TX also!
It is highly recommended to have an USB-SERIAL-CABLE-F (or similar product) at hand when
debugging – the video output is not always reliable and if you set wrong display settings you might
be unable to recover the settings without a proper UART0 connection.
For more information please refer to chapter “2.5 Interacting with the board”.
6.2 UART0 pins
The UART0 interface might be used for serial communication between the board and a personal
computer by default. In the case of a video output problem a cable might provide the needed
feedback and greatly reduce the efforts needed to repair the board or to adjust the software setting.
Note that by default only UART0 is defined as a port suitable for serial debug. You can use our
USB-SERIAL-CABLE-F for debugging.
Even when A20-SOM is mounted on A20-SOM-EVB the default debug port remains UART0
(despite that it gets additional pins on the big board also for easier access).
UART0
Pin # Signal name Processor pin
1 UART0-TX A7
2 UART0-RX B7
3 GND -POWER CIRCUIT-
4 GND -POWER CIRCUIT-
5 5VEXT -POWER CIRCUIT-
Page 22 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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