ADC timing

Sebastian20000 · Joined: 09 Nov 2007 Posts: 12

Hi,

I am beginner in programming pic and got a question with the ADC.
How can I read an analog value
everey 0.0001s into the A/D?

Is it sufficient to write:

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

Sebastian20000 · Joined: 09 Nov 2007 Posts: 12

yes you´re right. But in general the sampling would function
like this?

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

The loop time won't be exactly 100 us, because it takes time to
do the A/D conversion, and also to execute the while() loop.

You could adjust the delay_us() value to make the loop time be
fairly close to 100 us.

However, if you have interrupts running, some of the loop times
will be longer than 100 us, because the PIC must go process the
interrupt.

frequentguest · Guest

You also only have to set the ADC channel once before the loop. No need to call set_adc_channel() every time through the loop, assuming you are using the same channel every time.

rnielsen · Joined: 23 Sep 2003 Posts: 852 Location: Utah

The only reason you need a delay is in case you change inputs. This gives the internal capacitor time to charge to the currently selected pin's voltage level.

Ronald

Ttelmah · Guest

Not quite true.
The internal capacitor, is disconnected from the outside world, when you take the reading. It needs the same time between successive readings (to allow it to charge to the external voltage), as when a channel is selected. If doing really fast successive readings, this must be taken into account.

Best Wishes

treitmey · Joined: 23 Jan 2004 Posts: 1094 Location: Appleton,WI USA

I agree with ttelmah