ADC external-Trigger Options

Timothy Smieja · ‎2017-10-11

Posted on October 11, 2017 at 14:34

I am using the STM32F427 micro and a Keil compiler and have a question about external and timer trigger possibilities with the ADC. I have ADC1 and 2 configured for dual simultaneous mode and scanning through 12 conversions. Three ADC conversions for each of four different dual ADC channel inputs.

We have a mode of operation where the ADC inputs being sampled will have a pulsed signal as the input being sampled. Is there a way we can make sure we trigger on the high pulse of each of the four separate ADC1 inputs? I do not think we can guarantee that the pulses on each of the four separate inputs are all high at the same time, but maybe. If we can’t, then we would need to trigger on each ADC1 channel input, which there are four different channels sampled. I believe I've heard the term cross-trigging used in this context, but not positive.

Any input or suggestions would be appreciated. Hope this makes sense. I’ve included a couple screen shots of the ADC cube configuration. There seems to be a little bug with cube as it retained some previous settings in the window display for ADC1, but the code is generated correctly.

Let me know if more information is needed to provide feedback,

Timothy Smieja · ‎2017-10-16

Posted on October 16, 2017 at 15:42

Anyone have any suggestions?

Zt Liu · ‎2017-10-16

Posted on October 16, 2017 at 16:12

I am curious about the waveform of your triggering pulses.

Would you like to share it?

Timothy Smieja · ‎2017-10-16

Posted on October 16, 2017 at 17:44

Sorry, I do not have any pulses to share yet, we are currently waiting for hardware. The high portion of the pulse could be set anywhere from 0.1 ms to one second, depending upon use. Once itâ€™s set, it should stay the same.

The amount of channels have the pulse could be all four or just one. The pulses are â€œturned onâ€� in a cascade fashion one after each other, so they probably will all be high right after the last channel is set, so that might be the time to sample the channels. The slower the pulse, the better chance of each channel having the high pulse when sampled. I just do not know if that will be possible with the 0.1 ms pulse. Hope this helps, and thanks for any advice.

Timothy Smieja · ‎2017-10-18

Posted on October 18, 2017 at 16:13

Anyone have any input on this question?

AvaTar · ‎2017-10-18

Posted on October 18, 2017 at 16:20

Would an EXTI interrupt do, software-triggering the ADC sample sequence within the handler ?

I never tried tried a direct external trigger for ADC.

Zt Liu · ‎2017-10-19

Posted on October 19, 2017 at 10:27

EXTI trigger for ADC is only limited to 1 pin or not, I just used this mode once ...

Feel like not so flexible as input capture.