ADC EXTEN register when using timer trigger (TRGO) Topic is solved

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ADC EXTEN register when using timer trigger (TRGO)

Postby faisal » Fri Sep 21, 2018 1:21 am

STM32L496

I'm using the ADC triggered with a timer using the timer's TRGO signal. How does the trigger polarity work in this case? The options are rising, falling, or both. It seems that the polarity is not relevant (as long as it is enabled in any way).

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Re: ADC EXTEN register when using timer trigger (TRGO)

Postby Giovanni » Fri Sep 21, 2018 10:19 am

Hi,

If I remember well, TRGO is a very short pulse, this is why you don't see any difference. Raising and falling edges are very close to each other.

Giovanni

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Re: ADC EXTEN register when using timer trigger (TRGO)

Postby faisal » Fri Sep 21, 2018 5:48 pm

Giovanni wrote:Hi,

If I remember well, TRGO is a very short pulse, this is why you don't see any difference. Raising and falling edges are very close to each other.

Giovanni


It's important if cycle accuracy is required. I was confused whether the polarity had to do with the timer compare or something. From what you're saying it has to do with the TRGO line itself. If so, it should be rising edge. Though, if that is the behavior, then wouldn't a TRGO event trigger 2 conversions if you set the ADC to trigger on rising and falling edges? Or in general does it ignore requests that are too close to one another?

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Re: ADC EXTEN register when using timer trigger (TRGO)  Topic is solved

Postby Giovanni » Fri Sep 21, 2018 8:46 pm

I agree that it should be the rising edge.

In case of "both edges" I think the falling edge is just ignored because the conversion would still be in progress after the raising edge, I don't see any evidence of buffering for triggers in manual.

Depending on the TIM clock and ADC settings, TRGO pulse could be made wider than the conversion time, I think it would cause 2 conversions in that case.

Giovanni


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