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I want to connect the STM32F446RE (in the bootloader mode) via USART with my PC to flash some hexfiles on it. Between the USB port & the STM (USART1) I got an USB to USART bridge (CP2102). I used the STM32CubeProgrammer to connect the STM32F446RE with the host.

Everything works really well, but only one thing is a bit tricky.

My problem is, that the connection is not directly established. I need about 2 or 3 trys before I can connect with the STM. After that it works without any further problems.

So my Question is how long does the STM wait for a signal on his RX line. I found no documentation whatsoever.The AN2606 and AN3155 from ST helped me with other problems but there is no time specified.

So if anyone could help me...

This is the errorlog: 12:01:53 : Response received from device: NACK 12:01:53 : Error: GETID command not acknowledged! 12:01:53 : Reemission of GetID command 12:01:53 : Response received from device: NACK 12:01:53 : Error: GETID command not acknowledged! When I try to connect again it works perfectly. No errors.

USART Connection: Baudrate 57600 Parity: even Data bits: 8 Stop bits:1

Melissa123
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  • can you elaborate on your 3rd paragraph? – Tarick Welling Jun 18 '19 at 10:13
  • Yes of course. Let me try to explain it step by step :) When I try to connect to the STM I get some Errors. 12:01:53 : Response received from device: NACK 12:01:53 : Error: GETID command not acknowledged! 12:01:53 : Reemission of GetID command 12:01:53 : Response received from device: NACK 12:01:53 : Error: GETID command not acknowledged! When I try to connect again it works perfectly. No errors. Nothing. So I'm a bit confused – Melissa123 Jun 18 '19 at 12:01
  • please add your updates to your question by [editing it](https://stackoverflow.com/posts/56645094/edit). (don't forget to format it using the formatting buttons). What software are you using to connect? ST has multiple programs to connect and did you try to connect using a CLI? – Tarick Welling Jun 18 '19 at 12:05
  • also have you tried a lower baudrate? `9600` and `115200` are some standard ones – Tarick Welling Jun 18 '19 at 12:10
  • Thanks for the fast answer. I'll edit the question :) I tried other Baudrates. No suucess. Same error. I used the STM32CubeProgramme. I didn't use a CLI. I'll try and let you know . – Melissa123 Jun 18 '19 at 12:19

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