gEDA-user: Moving ADC data around

[Stuart Brorson]

On Mon, 11 Dec 2006, Peter TB Brett wrote:

> Hi folks,
>
> Slightly off-topic, but I need some suggestions: I'm currently building an ADC
> board to go with an existing microprocessor board I have available. It's
> going to have eight 100 kHz 12-bit serial ADCs.
>
> Now, the problem I have is that I want to read from all eight channels
> simultaneously and at regular intervals, but I have no control over how often
> or regularly the microprocessor will request data.

My thoughts, for better or worse:

Use a SAR A/D, which allows you to trigger all A/Ds at once using a
TRIG line.  (The usual sigma-delta A/D is free-running, so it just
gives you the value most recently read, which can lead to read-skew.)
The A/Ds will then hold the values you want indefinately in their
internal regs.

Then get rid of the CPLD entirely, and use the PIC to do all the
bit-banging necessary to transfer the data out of the A/Ds and to the
host uProcessor.

Stuart