I am trying to understand how the over sample hardware works on the ADC.

[LHarr.1]

My setup is I have timer 15 triggering ADC1 at a fixed frequency - say 1MHz

I have 4x over sample ratio set and the single trigger for all over sampled conversions set so I only get 1 DMA transfer for per 4 samples.

So with 4x over sample and 1MHz trigger rate.

Questions

• Do I get 1 sample per microsecond or 1 every 4 microseconds.
• Does the ADC sample the input once at the beginning of the 4x over sample process or does it re-sample the input on each of the over sample conversions..

[Uwe Bonnes]

You do not tell what STM32 you use for oversampling. I assume you use a STM32 with internal oversampling. Then you will get 1 value every 4 microseconds, but the data is samples every microseconds.

[TDK]

It will sample at 1MHz and give you results at 250 kHz.

[LHarr.1]

Yes it's the SM32H7 series.

Great thanks for that. It's what I was concluding w.r.t. the 1 sample every 4 uS. What I am still not sure of is : does it re-sample the input (recharge the sample hold capacitor) on each conversion or once every 4 conversions. If it's on every conversion then I am not sure this works when I am sampling a quickly varying input and I should probably just over-sample at a higher rate and filter without the help of the hardware.