Request for comments: SigmaTel STMP3xxx-based targets

[intgr]

The SigmaTel STMP3xxx SoC chip appears to be a quite popular embedded audio player chip; it contains all the essential functions of an MP3 player. I have set up a preliminary wiki page at SigmaTelStmp3xxx.

Chips from this series are used in MobiBLU DAH-1500i (MobibluPort by Michael Sanders), Zen Nano, iAudio I5/G2/U2, Apple iPod Shuffle, and many more.

I would personally be interested in porting Rockbox to this chip, although given my limited experience with embedded development, I am not going to pull it off it alone. I know that Nicholas Sanders, who set up the MobibluPort and MobibluInfo wiki pages had the same thought in February this year, but I have no means of contacting him. Advice or assistance from experienced developers would be very appreciated.

Information about the hardware on Google and other sources is far from scarce -- with some effort, you can even turn up hardware schematics and pretty comprehensive datasheets. However, information about programming the device is more difficult to come by.

All chips in this series contain a "Motorola DSP56004-compatible" DSP core, powerful enough to decode MP3 and WMV (and probably much more). It is unclear whether the chip core is limited to DSP56k instructions, or has been extended to make it a more sane environment for audio player development. The original DSP56k is a 24-bit architecture with 16-bit pointers (with 24 bits being the smallest addressable unit). There are several ancient ports of GCC 1.x to the dsp56k architecture (listed on the wiki page), although none of them would seem to be of "professional quality".

The firmware updater for my device (Philips Rush SA230), comes with an unencrypted and unencumbered firmware image (with plain ASCII strings which can be modified without the updater complaining), and the upgrade process apparently involves booting off the PC over USB, before actual flashing -- making it a very safe environment for hacking and testing.

In case anyone has immediate questions, I can answer by PM or on the Rockbox IRC channel.

[RobertWagner]

Hi, did you check out Motorola's compiler port for GCC

http://www.idiom.com/free-compilers/TOOL/C-22.html

BR
Robert