Hi GSMForum,

I hope it is okay for the admins here if I write in english because that's the only language I can speak / write reasonably well besides german.

So as far as I understood correctly this forum is all about "hacking" phones, e.g. custom firmware.

I am a software developer but in my spare time I mostly do PCB design, low level software, microcontroller etc.

My current project is to create a custom PCB based on the MT6205B, which was released in 2003 by Mediatek. It was used in many old phones (I guess, given that is has GSM capability). I specificly chose the MT6205B because it is not too complex in terms of handling all the hardware it has built into it.

I have the MT6205-datasheet and schematics for a chinese phone which uses the MT6205, so that's the kind of documentation my project is based on.

"Custom PCB" also means custom software! My short term goal is to get the CPU with custom code + external ram + external flash working - GSM is more of a very long term goal.

Unfortunately there is not much information about how to get my own software into the CPU. What I could get from the datasheet is:

  • there is an external pin 'BOOT' which defines whether the CPU boots into 'Factory Flash'-Mode or into 'Normal Operation' (which just means that it's fetching code from external flash)
  • 'Factory Programmming' is done via UART1 (unfortunately no information at which BAUD rate)
  • The code transferred over UART1 is then stored in the internal SRAM of the MT6205B and acts as a 'Bootloader' which then initializes external flash
  • As soon as external flash is initialized it is possible to send the firmware over UART1 into the Bootloader which then puts the firmware in external flash


What I know so far is that there probably is some kind of proprietary mediatek-header for both the initial bootloader and the firmware
I didn't find any information about the header but it's for sure that without a correct header it won't be possible to get anything into internal SRAM.

So after this long text I basically just want to ask you guys if anyone here has any information about what kind of header Mediatek is using for their bootloader! I guess that they are basically the same for all their low-level MT62xx chips which were released from 2003 until 2007 (according to wikipedia).


Any help is very much appreciated