Turning cheap GSM development board into opensource BLE mobile phone

Turning cheap GSM development board into opensource BLE mobile phone

I saw that Ai Thinker that developed ESP8266 has some new modules, and after a bit of search found cheap  GSM development board


I have found all documentations and source code for 8051 chip.

I have tested original code and it is not working as it should, you cannot enter number, you cannot delete no. when you enter it wrong, it stops responding after few seconds and then just type some numbers, so I decided to upgrade it with some arduino compatible chip.

I had two candidates for this module, first was STM32, and second was nRF51 chip.

But then if I chose STM32 I will not have bluetooth :( so nRF it goes …

I wanted board with nRF with as many pins possible and I have chose this module


After that I needed to remove original MCU and connect wires to nRF board.

At first I have used some bad USB soldering iron so I broke one pin, but quickly after that I was in my lab with normal soldering iron.

And this is ultra-fast prototyping so there is no time for fancy soldering :)

It is all one week after job work …

For now pictures are here


and some video progress


Today I have manage to get serial to work at 115200

I manage to get serial receive on one pin, so now I can start phone by waiting ready message for modem…

I also solder mic and speaker and  manage to talk if I call from BLEntaPhone

On call BLEntaPhone is now beeps and blinks blue LED ;)

Small presentation …



  1. What kind of wire, soldering iron/tip and solder did you use for those tiny connections? I’m not sure i could pull that off.

    • I have used some ERSA SMD soldering iron, yes it is hard to solder, but wire by wire and I manage to get it …

      • I will try to make some opensource board for this so you will need to solder module or chip only. For a few pcs I could even solder nRF on board, rest is easy…

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