Unable to flash STM32F401RET6 from ST-Link Utility or STM32CubeIDE

dreamcoder · ‎2022-01-24

I have successfully tested a prototype with the Nucleo F401 board and I have now moved the design to a custom PCB but I cannot program the microcontroller. The microcontroller STM32F401RET6 is not detected in the ST-Link Utility tool or in the STM32CubeIDE. The 3.3V is supplied to the MCU correctly. There are no peripherals connected to the board at the moment.

Did I miss any connection here?

I have tried these: connect VBAT to 3V3, changed C7, C8, C9, C10 to 100nF, changed C12 to 4.7uF for VCAP1.

The MCU is still not detected and I tried with my second board too. This rules out the MCU being broken.

dreamcoder · ‎2022-01-25

Yes, they are genuine since I am using the microcontrollers from the Nucleo F401 board. The layout for my design looks fine too. It is very similar to the F405 board that I created. The only difference I can see is that I am not using SWO pin on my F405. Do you think there is any effect by using this pin in my F401 board?

Peter BENSCH · ‎2022-01-25

No, SWO is optional.

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dreamcoder · ‎2022-01-25

Thanks for the clarification. I still did not manage to find out the issue on this board. Are there any specific things I could investigate further?

Peter BENSCH · ‎2022-01-25

VIN is probably 5V?

Cap C12 is a ceramic one (MLCC)?

Can you see the SWCLK and SWDIO signals with an oscilloscope on pins PA13/14?

Can you see a low pulse with an oscilloscope on the NRST when you try it with the STM32CubeProgrammer and Connect under Reset?

BTW: the ST-Link Utility is not recommended anymore, it is recommended to use the STM32CubeProgrammer instead.

Mmm, after that it gets tedious: you could transplant the STM32 to a NUCLEO and check if it works there - in this case the problem is definitely with your proto board.

Regards

/Peter

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TDK · ‎2022-01-25

I don't see 0.1uF decoupling caps on VDD. Doubt that's it though. I would guess a bad solder joint somewhere in a critical path.

VCAP should be 4.7uF since there is only one VCAP pin. Doubt that's it as well.

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dreamcoder · ‎2022-01-25

I changed them both to the correct values, still nothing.

dreamcoder · ‎2022-01-26

Yes, VIN is 5V. C12 is MLCC. Should this be an electrolytic capacitor?

I can see a certain signal on SWDIO line but not on SWCLK.

I can see a low pulse on NRST when I hit connect on the STM32CubeProgrammer.

Peter BENSCH · ‎2022-01-26

MLCC at C12 is fine.

However, it is not a good sign if there is no signal on SWCLK. If you look at a known good board, you will see clock pulses there. Please trace this line to your debugger to make sure there is no contact problem.

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