RK3188 Quad Core Cortex-A9 Android stick teardown

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My RK3188 Android stick arrived yesterday and needless to say it was disassembled immediately.

What I like is the big external WIFI antenna it makes reliable connection to the WIFI router even if the signal is weak.

What I didnt like: there was tiny 0.8 mm thick aluminum plate placed on top of RK3188 with … double side adhesive tape 🙂 c’mon guys this tape is thicker than the aluminum plate, what termal transfer will it have??

This stick was $30 cheaper than A31 stick I bought one week ago, but when I opened it I could see why – it have only 1GB of RAM not 2GB as A31 stick had!

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Something else I missed in the brief datasheet is that RK3188 have no native HDMI but only RGB LCD interface, so it needs IT66121 RGB-HDMI transciever to connect to HDMI TVs. No signs of HDMI TVS protectors like in all cheap Android sticks, these are pretty expensive and should not be wasted 🙂 you can see there is provision for them on the PCB but they are no populated, you better pry your TV have no static electricity charge when you connect your Android stick to it 🙂

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there is something else which always puzzles me when I open these sticks. When we design our OLinuXino schematics and follow all rules we place between 120 and 150 filtering capacitors to all voltage / GND points – and these chips have *LOT* of voltages, for the cores, for the peripherials, for the output buffers, etc etc.

All these sticks have no more than 30 capacitors at all! What does this means – less noise immunity, and sometimes digital parts could latch-up but who cares when these sticks are so cheap 😉

A31 Quad Core Cortex-A7 Android miniPC CS868 teardown

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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.

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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:

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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.