[sdiy] dsPIC interfacing with multiple CODEC chips

[Seb Francis]

Hi Steve,

Thanks for your response .. it looks like it is as I feared.

>
> It IS possible to connect several devices, but they have to be 
> configured as a Time Division Multiplexed system, and most of the 
> cheap/easy to get hold of/popular converters don't support that way of 
> working. Some of the newest multichannel parts (intended for surround 
> sound equipment) do, though. See the Cirrus/Crystal website, but good 
> luck in buying parts like that in small quantities.
>
It is a Cirrus part (CS4272) that I'm intending to use, but it doesn't 
look like it supports this mode :-(

> Try as I might, I couldn't come up with a solution to this other than 
> using a programmable-logic interface between the converters and the 
> PIC, at which point it seemed easier to look for another DSP.
Since the serial clock normally runs at 64x FS, there is actually room 
for 2 x 16bit x 2channels in each frame time, so I reckon it would be 
possible to put some glue logic in between, like some kind of counter & 
switch that counts the L/R clock and flips the connection every frame.  
But this is certainly 2 extra chips, and could be unreliable .. I'd 
rather just use an extra PIC instead.

>
> If you solve it, do let us know! I ended up using the Alesis/Wavefront 
> AL3101, which is crappy in other ways but at least has four stereo 
> codec interface ports (I needed four) and is optimised for audio.
>
Well, I think I'm going to solve it by using 2 PICs.  It's not too big a 
deal - the only tricky part will be making them talk to each other as 
they will need to share the same LED display to show the delay time when 
a knob is turned.

Cheers,
Seb