STM32 DFSDM - simultaneous sampling of multiple channels

[FLast.17.70]

Posted on September 25, 2017 at 15:11

I am a bit confused about the capabilities of the STM32 DFSDM module. The documentation says (section 17.3.77) that the channels selected for are converted one after another, but is it possible to sample multiple channels simultaneously?

To approach the question from a slightly different angle, with STM32 devices that have dual or triple ADC it is possible to sample two or three analogue signals simultaneously by running the two (or three) ADCs together. So it is possible to sample two or three analogue signals without any phase difference, at exactly the same time. Does the DFSDM module have this capability?

I need to sample up to 4 external delta-sigma modulators at exactly the same time, without any phase difference. The data sheet is not clear whether this is supported.

[waclawek.jan]

Posted on September 25, 2017 at 15:24

The documentation says (section 17.3.77)

Which chip?

JW

[FLast.17.70]

Posted on September 25, 2017 at 15:34

STM32F76xxx. The document I am referring to is Reference Manual RM0410, section 17 describing the DFSDM module.

[FLast.17.70]

Posted on September 25, 2017 at 16:17

So effectively the DFSDM module in the 

STM32F76xxx can act as if I had 4 ADC modules? This would be great. The application would be for a dual channel FOC, so I would need to sample four phase currents simultaneously. I guess I'm not too far from the truth if I assume that this is one of the intended application areas for the DFSDM, especially taking into account that ST is strong in 3-phase motor control...?

[waclawek.jan]

Posted on September 25, 2017 at 16:02

There are 4 filter modules there, so you can perfom 4 simulataneous conversions.

The confusion arises from the possibility to multiplex several input channels into one filter, which is what you don't want.

JW

[waclawek.jan]

Posted on September 25, 2017 at 16:26

So effectively the DFSDM module in the

STM32F76xxx can act as if I had 4 ADC modules?

Yes.

https://community.st.com/0D50X00009XkZjHSAV

JW

[FLast.17.70]

Posted on September 25, 2017 at 16:39

Thanks. That's great news.