multiple ADC channel conversions with timer int

[starfire151]

I searched the posts related to this but did not see anything specific to this question...

Is it possible to start a conversion on two ADC channels and then, a time delay later, read them out? For instance

from the background:

set_adc_channel(0);
set_adc_channel(1);

and then enable a timer interrupt which interrupts a sufficient time later:

from the timer interrupt service routine:

x = read_adc(0);
y = read_adc(1);

From what I've seen in the data sheet and what has been posted, most of the time the set_adc_channel() and read_adc() operations are done sequentially. Is there any way to get the channels to convert at the same time?

[bkamen]

It depends on the PIC.


Typically the answer is "no". You need to read the datasheet for the device you want to use very carefully.

For example: most PIC18's only have 1 sample/hold and 1 converter. However, the 18Fxx31 has 2 sample/holds and 1 converter.

This means triggering a sample can cause both sample/hold units to sample, then the converter performs it's work on S/H1 and then S/H2.

You get 2 samples at interrupt time (if you have it set that way - but there are more options), but they were arrived at sequentially.

Some of the higher end PIC's (like the 16bit/32bit PIC's) have more than one converter. So they could deliver more than one channel worth of values for a given sample trigger.

If you're using PIC16's or 18F's, most likely you can only do one conversion on one channel at a time.

-Ben
_________________
Dazed and confused? I don't think so. Just "plain lost" will do. :D

[PCM programmer]

The 18F4431-series PICs have dual-channel simultaneous sampling ADCs:
http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en010288

This thread has sample code for it:
http://www.ccsinfo.com/forum/viewtopic.php?t=42256

[starfire151]

Excellent. This gives me something to go with.

Thanks for the replies.

[bkamen]

[gpsmikey]

[bkamen]