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 ;)