Interrupt when ADC is converting?

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Can an interrupt occur when the ADC is converting?
What happens with the conversion?

:roll:

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Yes it is possible, why not?
I think the conversion will continue its normal flow.

Real men don't use backups, they post their stuff on a public ftp server and let the rest of the world make copies.

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What is the fastest ADC conversion possible?

:roll:

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Maximum input clock frequency is (theoretically) 200 kHz.
You may set a higher frequency, but you'll get a lower resolution.
I am using 460800 Hz, as I currently need only 8-bit ADC result (MSB).

Real men don't use backups, they post their stuff on a public ftp server and let the rest of the world make copies.

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groenhen wrote:
Maximum input clock frequency is (theoretically) 200 kHz.
You may set a higher frequency, but you'll get a lower resolution.
I am using 460800 Hz, as I currently need only 8-bit ADC result (MSB).

So will the fastest 10-bit conversion time be 5usec?
Because the datasheet says 65usec - 260usec.

:roll:

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Highest conversionspeed with int. RC on @ 8MHz is 3.25 usec. (prescale cannot be 1, only 2.)

8MHz/2*13

Is this right?
But at 200kHz there are no errors, right?
So taking 10bit samples is impossible at such a high speed?

8)

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I'm not sure if this is true, but some guys assert that max. sampling frequency also depends on:
- Vcc (voltage that powers your AVR);
- Vref (ADC voltage reference);
- the nature of the sampled signal (@ ADC input).
I don't know where I saw that, but you may use the "Search" on the left of page if you're interested (it isn't a very recent post).
Anyway, in the most recent version of CodeVisionAVR, I did notice that the CodeWizard has increased the maximum ADC clock frequency to 250 kHz [!]. Guess why?

Real men don't use backups, they post their stuff on a public ftp server and let the rest of the world make copies.

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Quote:

I did notice that the CodeWizard has increased the maximum ADC clock frequency to 250 kHz [!]. Guess why?

I give up and have no guess. Many people requested it, since they commonly use that when using 4/8/12/16MHz clocks? New AVR models have moved the recommended frequency to 250kHz?

What is interesting are the ADC specs on the Atmel AT91SAM7S series--2us conversion with 5MHz ADC clock for 10 bit res (see below). I figgered since >>Atmel<< knew how to build a faster ADC we'd soon see it on AVRs. Nothing yet...

Quote:

37.7 ADC Characteristics
Table 37-16. Channel Conversion Time and ADC CLock
Parameter Conditions Min Typ Max Units
ADC Clock Frequency 10-bit resolution mode 5 MHz
ADC Clock Frequency 8-bit resolution mode 8 MHz
Startup Time Return from Idle Mode 20 µs
Track and Hold Acquisition Time 600 ns
Conversion Time ADC Clock = 5 MHz 2 µs
Throughput Rate ADC Clock = 5 MHz 384 kSPS

Lee

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.

Last Edited: Mon. Dec 5, 2005 - 01:04 AM