A31 Quad Core Cortex-A7 Android miniPC CS868 teardown


Few weeks ago I ordered A31 Android stick on ebay for $98 and I got it in the post today. The price is high compared to the other Android sticks, but the 2GB DDR3 memory and 8GB NAND Flash with the current crazy memory prices justify this. A31 price alone is quite modest as you can see even from our web shop and not so higher than A10-A20 https://www.olimex.com/Products/Components/IC/A31/

so you may bet the price of the memory in this miniPC is more than the four core processor itself

The product name is CS868 Android miniPC made with A31 quad core Cortex A7 processor from Allwinner.

The datasheet of A31, user manual and reference schematics are in our GitHub https://github.com/OLIMEX/OLINUXINO/tree/master/HARDWARE/A31-PDFs

As we evaluate the possibility for OLinuXino with four core processor I ordered this one miniPC at least to may experiment with the software support.

Needless to say the first thing I did was to open it and look inside.


if you do wonder what are these spots on the NAND flash and one of the DDR3 chip, this is traces from the glue which is used for this huge aluminum heatsink placed on top of A31

the power supply adapter is 5V 2A i.e. 10W and if these 4 cores take x 1.2-1.3W as A1x the radiator is must for this BGA package.

and look at the back:


as you can see on the picture A31 comes with 2GB of RAM and 8GB of NAND flash, as the databus is 64 bit wide it reads and writes the memory content twice faster than A10-A20 where the bus is 32 bit and four times faster than A13-A10S where the databus is only 16 bit wide.

What I do not like in these Android sticks is the use of micro USB connectors, this is so unreliable connector that I do not understand why manufacturers still use it specially for power supply where frequently plug unplug operations are necessary. mini USB is thousands times more reliable than micro USB connector.

Basically beside the AXP221 PMU, DDR memory and NAND memory and WIFI module there is nothing else inside. This is shame as this chip have over 300 GPIOs and interfaces which stay unused.

Gigabit Ethernet, UARTs, SPIs, I2Cs, CSI, LCD, LVDS, to name few.

12 Comments (+add yours?)

  1. Beat
    Jul 05, 2013 @ 19:14:04

    Since many Cellphones have microUSB, i am not shure if this is really not reliable enough…


  2. funlw65
    Jul 05, 2013 @ 19:54:35

    From my user experience, miniUSB will start develop contact problems very fast! It was a failure! This will be the problem nr.1 with Olimex products if that is used instead of microUSB. The microUSB is tide and will resist in time longer than that stupid miniUSB. Yes, it needs a delicate manipulation, but we (users) already know that and we act accordingly.


  3. OLIMEX Ltd
    Jul 05, 2013 @ 20:03:19

    I cant agree with these statements as I believe my eyes
    miniUSB have solid pads and can be soldered reliable to the PCB, microUSB have smaller pads and if you push more hard it will just peel off the PCB, this usually happens with these Android sticks, the microUSB desolder after few insertions
    with the phones you have solid plastic which do not allow you to twist the plug connector but these Android PCs have cheap plastic cases which are supportive to the microUSB connector and allow cable to twist around


    • funlw65
      Jul 05, 2013 @ 21:04:31

      Yes, it is builder’s job to mount the microUSB in a way that it will be safe – and you talk from a builder perspective. I have nothing against what you said. But is also a fact that miniUSB will wear off sooner than a microUSB when you insert the USB cable many times – it is about the contacts inside, between the cable and the socket, not about what will happen on the PCB traces – that is your problem as a constructor.


    • Max
      Jul 08, 2013 @ 10:17:38

      That’s an unfortunate problem specific to dongles – they place the entire weight of the device on the connector, and worse than that, they place it on a lever. Needless to say what happens when said dongle has a further cable(s) hanging out of its other end… Connectors in phones would start breaking really quickly too if one were to inset the charger cable into a wall and just stick the phone onto it, hanging in the air. It’s not like there are many charging docks without any support for the phone, isn’t it – yet this is somehow considered normal for dongles…


  4. John
    Jul 05, 2013 @ 20:08:32

    Are these patches 3.3, d+, d-, and gnd the uart?


    • OLIMEX Ltd
      Jul 05, 2013 @ 20:18:27

      the pads are for WiFi module, seems they have two types one smaller which is installed and one bigger which these pads belong to I guess they are wired in parallel I see there GND 3.3V D+ D- and LED


  5. David Burke
    Jul 08, 2013 @ 08:33:34

    Cannot wait until you do a four core board with Debian ( Mate Desktop ) with 2GB of Ram, have no need for Nand Flash, just SATA, SD Card and USB. 😉

    I see it as the reason to dump the PC on our office desks and also out in the CNC Workshop. They will be so much easier to use and no need to try to find replacement bits as you just insert a new board if something goes wrong 😉 The lack of OpenGL support could be a problem though, but not critical as we can use Mesa I suppose.


  6. Tim
    Jul 17, 2013 @ 21:45:24

    Wouldn’t most of the mini-USB vs micro-USB port issues not be an issue with this device? Phones have issues because we plug them in and out every day, sometimes many times a day. A mini-pc will be plugged in once and that’s it.


  7. adem
    Oct 30, 2013 @ 02:10:49

    does any one know of new firmware updates for this device i think its been abandoned there has been nothing for about a year now the 4.2 firmware does not go past boot screen


  8. paddlestroke
    Nov 13, 2018 @ 16:43:22

    Is an olinuxino A31 coming the future? I saw there’s a A33 but I was looking to use HDMI


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