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HWhit.1
Associate III
August 23, 2026
Question

Problem with configuring DAC1_OUT1 and DAC1_OUT2 to drive COMP1 and COMP2 INP- by internal connection

  • August 23, 2026
  • 1 reply
  • 5 views

Hi,

I have been using a NUCLEO-H7A3ZI-Q board in a research project for a magnetic spectrometer. The input the the Nucleo board is two short pulses which I have for a year or so, been using to generate trigger pulses using the INP inputs of  COMP1 and COMP2 with INN connected to DAC1_OUT1 and DAC2_OUT2, respectively by on-chip connection. The external outputs of COMP1 and COMP2 drive TIM1 and TIM3 that trigger ADC1 and ADC2. 

 

I used STMCubeMX 6.17.0 and STMCubeIDE 2.1.0 for authoring the code. 

 

I I needed to recompile a new version and I experienced that the output from COMP1 was not working with random fluctuations between 0 and 1. Previously, the COMP1 output was sharp pulse with a duration the input pulse was over the threshold set by DAC1_OUT1. The COMP2 output behaves as it should.
 

I tried to check the output of DAC1_OUT1 and DAC1_OUT2. Only the latter could be directed to an external pin and this worked as intended and produced the signals as expected. DAC_1_OUT1 was restricted to on-chip connections. It seems the problem is that the internal connection DAC1-OUT1  → COMP1_INN is no longer being made. . However, on-chip connections did not previously need the external pin to be unused. (Pin PA5 is used as TIM5 ETR input.)


My questions:

  1. I suspect this is a bug in STMCubeMX since it has just appeared? 
  2. Is there a way to manually work-around the internal connection configuration e.g. by direct writing to the registers as part of the set-up procedure.

    Many thanks for any help on this issue.

1 reply

TDK
August 24, 2026

Show your code or go off of one of the existing examples.

Yes, you can write to registers to interact with the DAC or any other peripheral.

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