How to use COMP1 and COMP2 in STM32H747I-DISCO board?

Louie88 · ‎2022-02-14

I could not figure out how I can connect a sine wave signal to the positive input of COMP1 or COMP2 comparators in STM32H747I-DISCO board. According to the STM32CubeMX the comparators positive inputs are on PB0 (COM1_INP) and PB9 (COM2_INP) GPIO, but I could not find PB0 and PB9 on any connector of the discovery board. Is there any trick how to use the internal comparators, or they are not accessible in this discovery board, which is pity.

Thanks for any help!

Louis

Peter BENSCH · ‎2022-02-14

Hi Louis,

As you said: a display is a different story and has nothing primarily to do with the original question. It would be best if you created a new thread for this.

BTW: Please also read our Terms Of Use, which apply to all our hardware tools, especially the restrictions and warnings.

If the question is resolved, please mark this topic as answered by selecting Select as best. This will help other users find that answer faster.

/Peter

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View solution in original post

Peter BENSCH · ‎2022-02-14

DISCOVERY boards are intended to investigate the functions of the respective STM32 and are therefore already equipped with plenty of peripherals so that you can test this extensively without having to build your own board. For this reason, only a few GPIOs are free for alternative use on the DISCOVERY boards. In your specific case, both the normal and the alternative pins for COMP_INP1 and COMP_INP2 are already assigned with functions for USB and display.

If you want not only to try out the functions of the respective STM32, but to have almost complete freedom in development, you should consider a NUCLEO board instead, e.g. the NUCLEO-H745ZI-Q or the NUCLEO-H7A3ZI-Q.

Good luck!

Regards

/Peter

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Louie88 · ‎2022-02-14

Hi Peter!

Thanks for the answer. Also thanks for the replacement suggestions but I think the nucleo-h753zi is closer to the STM32H747I processor except it has a single M7 core. (We do not really need two cores processor)

The display is a different story. Can you suggest a LCD module which can be driven from the the nucleo-h753zi board? We do not need too fancy LCD, touch screen is not needed, just the graphical 640x480px.

Thanks,

Louis

Peter BENSCH · ‎2022-02-14

Hi Louis,

As you said: a display is a different story and has nothing primarily to do with the original question. It would be best if you created a new thread for this.

BTW: Please also read our Terms Of Use, which apply to all our hardware tools, especially the restrictions and warnings.

If the question is resolved, please mark this topic as answered by selecting Select as best. This will help other users find that answer faster.

/Peter

In order to give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.

Louie88 · ‎2022-02-15

Hi Peter,

The "best" answer is that STM32H474I-DISCO board with all its fancy features does not support using the built-in comparators because of the lack of GPIO pins. Really the best answer? I would say it is a serious design bug. But this is not your fault. Thanks for the best answer!

Louie

Peter BENSCH · ‎2022-02-16

I can understand your annoyance, but it is not a fault, it is based on a misunderstanding of the purpose of DISCOVERY boards.

All STM32 offer many more functions than can be simultaneously fed out via the pins. For this reason, a design must be carefully planned to achieve all the desired functions via the available pins. For a new development of a design, the use of a NUCLEO is also recommended for this reason.

Good luck!

/Peter

In order to give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.