FM radio on a genny

[evildragon]

How hard would this be to pull off? I had this idea while listening to a small chip that is an FM radio on-a-chip..

It has the following pinouts,

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     --- 
GND -| |- L-Audio
Ant -| |- NC
GND -| |- R-Audio
A1  -| |- D1
A2  -| |- D2
A3  -| |- D3  (Seems to be OUTPUT, nothing goes IN on this pin)
FMS -| |- 3.3v
     --- 

FMS:  FM Stereo LED indicator

Sadly, I had to find these pinouts the hard way, as it came with it's top surface of the chip sanded off, and I can't read the part number..

but, this seems to be it's format, receiving nothing but direct commands, and lacking volume controls..

CH+
CH-
CHxxx.xx (allowing input of channel frequency, and seems it MUST be 3.2 format)
DX
LOCAL
AUTO (I assume auto is the selection of DX and local by itself, whatever those modes do anyway)
POLL (when this command is provoked, it sends back the following:

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FM/DX/ST/106.7MHZ/-||||||||x-

from what I understand, the weird lines at the end is actually a signal strength indicator..)
FREQ-US (this seems to make it channel surf in .2 odd increments)
FREQ-BRIT (this seems to make it channel surf in .1 increments)
and finally
HD-ENABLE (as far as I know, this chip has NO HD-Radio functions, but I could be wrong? enabling it makes it sound like MPEG distortion, and a small 4 second delay on sound)

oh, and the data MUST be sent to it at 1KB a second.. any faster or slower, and the chip fails to receive data.. when you do a POLL command, it constantly sends the poll data, updating at 1KB/S speeds, and updates every 3 seconds..

can this be put on a Genny cartridge, while still having a ROM chip on the cartridge to control it?

EDIT: oh, and if this is possible, how can I have the Genesis parse the POLL data? The structure seems to change.. for example:

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FM/DX/ST/106.7MHZ/-||||||||x-

but, on another channel, it shows this:

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FM/DX/95.3MHZ/-|||xxxxxx-

EDIT2: Ehh, just had something in mind.. Why the hell does this thing need address lines? It's not a memory chip or a CPU!

EDIT3: This is what the IC sounds like decoding HD-Radio.. sounds like crap to me... (this is with the chip on a test board, with NO address lines connected.. it seems to run fine without the address lines.. so for what they do, I have NO idea! They do seem to change the POLL data around though)

http://blackevilweredragon.spymac.com/hdradioic1.aifc
http://blackevilweredragon.spymac.com/hdradioic2.aifc

[TmEE co.(TM)]

You and your crazy ideas...

It is possible to connect it and control it with MD, but the limitations of the radio will make it little difficult.

[evildragon]

the limitations, i hate limitations! :p

anyway, I found the purpose of the address lines.. they are nothing more than mode changers, and are not truly address lines..

for example, it seems to have 3 modes..

1. Fixed Poll Data Mode
So instead of the odd changing of poll data from channels like above, is a station isn't coming in stereo, instead of "ST" being totally missing, it just says "NST"..
2. AM Radio Mode
This doesn't seem to work, this IC must lack this feature, but POLL data does show AM instead of FM, and shows KHz.
3. 5.1 Downmix Off
This is for HD-Radio I'm assuming as they can come in 5.1... I figure it's a disable mode, because the songs seem to lose sounds..
4. Mute

Those are the address lines functions.. just proping the lines make it change.. i wonder why they didn't just use the data lines for that, but oh well..

[evildragon]

oh an awesome update!

There's a 4th mode via the address lines!

The 3rd data line can also act as a RAW HD-Radio output, taking the digital signal and outputing it as the format it's sent in, requireing an external decoder..

I wonder how cool it would be to have the Genesis decode it and play it back via it's Sega CD's PCM output, allowing cleaner audio than going through the Genesis' op-amps..

Could the Sega CD have enough power to handle it? this is the format: http://en.wikipedia.org/wiki/High-Definition_Coding

Also, there IS a 5th mode, which includes POLL data along with DATACASTING.. This would allow the Genesis to show the station call sign, AND the song being played...