Rockbox

audio_set_output_source sets the input that that output is connected to (ie. which input is heard) so it is possible for instance to process audio from a source and play it back through software (audio_input_source might be FM while audio_output_source would be playback) would rather than directly piping something direcly back to the output.

+ unsigned int spacing = spacings[write_bytes[7] & (3 « 4)] ;
should be [(write_bytes[7] » 4) & 3]

The datasheet mentions that some bytes should be not modified when written (first read and then written back).
Doesn’t it make more sense to read all the registers (in a si4700_init() for example) and then modify individual bits, instead of using a built in list of registers values?

New version, implements detection, I don’t know if there were any gigabeat S’s that didn’t have radio though.
Fix the array indexing bug funman spotted and implement the suggested si4700_init().

Edit: updated patch without stupid mistake :)

   gbs_fm_v7.diff (17.2 KiB)

spotted other things :

* you should read all the registers to a temporary buffer and copy to write_bytes, because you start reading from register 0xA and write to 0×2 * you should write your copyright in si4700.c ;)
* the #endif comment of the si4700 case in tuner.c is for another tuner
* I don’t see the power up bit set in si4700_init() (I see it in si4700_set() however)
* si4700_init() is indented on 5 spaces

Also are the GPIO interrupts needed?

New version fixes funman’s comments except powering up in the init,
it should remain in the RADIO_SLEEP case in si4700_set.
Make the detection actually work, leave softmute enabled, lower the output
volume to be a little closer to playback, fix a couple of mistakes.

   gbs_fm_v8.diff (17.5 KiB)

Fix an off by one error, should use 10 bits for setting channel, thanks to bertrik for spotting!

   gbs_fm_v9.diff (17.5 KiB)

Works well on my Gigabeast, save for two quirks:

1) The FM radio’s volume is quite loud, much louder than normal playback should be.

2) Entering the main menu from any other screen seems to take a second or two longer than it should.

Other than that, great job! :)

New version of the patch, with a few fixes by myself and Nils after some brainstorming on IRC:

1) Fixed a small bug in si4700.c, where returning to the main menu from any other menu or the file viewer would take a second or two longer than it should; this was done by moving fmradio_i2c_read from si4700_get to the RADIO_STEREO case.

2) In audio-gigabeat-s.c, fixed the passthrough volume to be a lower value; originally it was set to 7, which was causing the radio to be much louder than normal playback (passthrough volume was +6dB at this point). Setting it to 5 now sets the passthrough volume to 0dB, which is much more sensible.

3) I set the VolUp and VolDown buttons to work as they do in the WPS on the FM radio screen as well. Please help test this.

   gbs_fm_v10.diff (17.7 KiB)