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Lukasz Przenioslo
Lukasz Przenioslo
Associate III
March 21, 2016
Question

trigger adc after counter is reached

  • March 21, 2016
  • 26 replies
  • 3688 views
Posted on March 21, 2016 at 23:50

Hello there,

I was wondering either in STM32F4 it is possible, to get a similar functionality to C2000 one, that can trigger an ADC conversion after certain counter valueon a timer is reached, like here:

https://www.dropbox.com/s/d6lonep1m3i5x4d/Zrzut%20ekranu%202016-03-21%2023.48.06.png?dl=0

(point CA, middle).

In stm34f4 I am using center aligned pwm mode. I can trigger ADC each time timer starts counting up/down or both. But I need to trigger the adc when the counter is halfway down or up. Is there a way to do this?

I would appreciate all help.

#timer #adc #synchronization
This topic has been closed for replies.

26 replies

Tesla DeLorean
Tesla DeLorean
Guru
March 21, 2016
Posted on March 22, 2016 at 00:59

If you have a spare channel in your timer, and that associates with one of the ADC triggers, then you should be able to set the CCR for the desired count, and that should fire each time it passes.

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Lukasz Przenioslo
Lukasz PrzeniosloAuthor
Associate III
March 22, 2016
Posted on March 22, 2016 at 07:15

Thank you for help. I dont have one but i will try to get one.

Lukasz Przenioslo
Lukasz PrzeniosloAuthor
Associate III
March 22, 2016
Posted on March 22, 2016 at 08:18

But is there really no way to make the counter count like this maybe?

https://www.dropbox.com/s/iw9gcw9kplbkg8n/Zrzut%20ekranu%202016-03-22%2008.18.08.png?dl=0

Tesla DeLorean
Tesla DeLorean
Guru
March 22, 2016
Posted on March 22, 2016 at 11:06

I thought that is how pwm centred worked, but not really a timer mode or function I've got much use for.

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Lukasz Przenioslo
Lukasz PrzeniosloAuthor
Associate III
March 22, 2016
Posted on March 22, 2016 at 11:50

I thought this as well! But the counter overflow interrupts are generated at the end of pulses...

Tesla DeLorean
Tesla DeLorean
Guru
March 22, 2016
Posted on March 22, 2016 at 14:09

Ok, but doesn't the timer provide an underflow/overflow indicator so you know which way it was counting?

I suspect you'll need to do some evaluation of what the counter is actually doing.

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Lukasz Przenioslo
Lukasz PrzeniosloAuthor
Associate III
March 22, 2016
Posted on March 22, 2016 at 14:23

In center aligned pwm mode 3 I can generate interrupts each timer counter starts counting up and down. So it looks like this:

[[this link/image has been flagged as malicious by our security scan software and has been deleted]]

With RED color i have drawn the counters levels. Red dots are interrupts. As you see I can generate OC interrupts only at the edges, not in the middle, because the counter doesnt stop/ start in the middle...

Lukasz Przenioslo
Lukasz PrzeniosloAuthor
Associate III
March 22, 2016
Posted on March 22, 2016 at 16:11

Is there a way to change this behaviour to get interrupts in the middle so they can fire ADC?

Tesla DeLorean
Tesla DeLorean
Guru
March 22, 2016
Posted on March 22, 2016 at 16:43

Sorry, I don't know...

The Update should fire at CNT=0

The Up/Down counter should go  22, 23, 24, 23, 22, .. In which case I'd suspect setting CCR to 24 would have the channel fire at the peak value.

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Lukasz Przenioslo
Lukasz PrzeniosloAuthor
Associate III
March 22, 2016
Posted on March 22, 2016 at 17:29

Ill try to figure this out, maybe using an additional timer. Thank you.

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