STM32H723 ADC DMA (PF7/PF8/PF9/PF10)

[SSchn.8]

Greetings,

Platform Details:

• GCC 10.3 + CMake
• STM32H723 Nucleo-144

I am currently a bit struggling with the ADC Conversion via DMA. My software is working with many other ADCs, but for some reasons, if I am using following ADCs, the values from the DMA-Controller do remain zero, even though the DMA transmission has been successfully finished:

• PF7: ADC3_INP3
• PF8: ADC3_INP7
• PF9: ADC3_INP2
• PF10: ADC3_INP6

If I replacing PF7 with PF6 it seems to work again as expected, therefore I don't expect any bugs from my side. Are there any known issues with the DMA controller related to those pins?

Kind regards

[TDK]

The DMA transfers data from the peripheral (ADC->DR register) to memory. It doesn't do anything with specific pins. The answer is likely elsewhere.

[SSchn.8]

So could you explain me then why other ADC3 Channels are working fine via DMA? I have not forgotten to configure the Channel. I also checked the Auto generated Code.

Even though the Pins PF7-PF10 would be grounded, i would at least expect some noise but each conversion is returning exactly 0 which is really strange because those pins are currently floating.

[TDK]

I don't know, probably a bug in your code or a misunderstanding in your interpretation of the results. You haven't posted anything to be able to diagnose.

> each conversion is returning exactly 0 which is really strange because those pins are currently floating.

Taking ADC conversions on pins that are floating and then attributing significance or importance to the result is not advised.

[waclawek.jan]

> each conversion is returning exactly 0

How do you know? Did you observe the ADC registers' content?

JW

[SSchn.8]

Here some more details. You can find the necessary DMA + ADC Configuration. I am using a std::vector to handle the incoming DMA Data. You can find a snippet of the local data in the "HAL_ADC_Start_DMA" Function (I am using the addresses 0x3000 0000 and above for the DMA transmission). @Community member​ . In the Memory View you can see, that only certain memory areas are being updated (The red ones). Channel 2, 3, 6 and 7 remain zero. All channels which are before/after are working as expected.

I don't change any CubeMX Configuration, I am just using the created source code and using the HAL-Handles in my application code.

Any idea what the issue might be?

[waclawek.jan]

> I am using a std::vector to handle the incoming DMA Data.

I don't use C++ and don't know what exactly this means, but dynamically allocated and re-allocated memory sounds like a potential source of problems.

Try conservative static DMA buffer allocation.

JW