AnsweredAssumed Answered

ST virtual com port issue in case of MCU reset

Question asked by belomutskiy.andrey on Feb 22, 2014
Latest reply on Sep 1, 2016 by AvaTar
I have a problem with serial-over-USB port reconnection after stm32f4discovery board reset (for instance, re-programming) - with the native USB controller port, not the uart dongles.

I have originally reported this issue to ChibiOS since I can reproduce this with a ChibiOS standard demo application, but they believe the issue is within ST VCP driver.

I wonder if anyone can maybe reproduce this issue without ChibiOS and, in case the issue is reproducible, how do we go from there?

Here are the detailed steps to reproduce:
1) make ARMCM4-STM32F407-DISCOVERY-MEMS ChibiOS demo (I am using 2.6.3 now but the same issue was present in 2.6.1 and probably before)
2) program ch.hex, connect micro USB cable. My windows 7sp1 has driver version 1.3.1, that's the latest version
3) connect to the serial port with putty - shell is responding as expected
4) keep putty open, reset stm32f4discovery with the black button
5) windows make the 'device disconnected/device connect' sound as expected
6) press any key in putty, PuTTy fatal error: error writing to serial device reported, as expected
7) close putty

Now the issue:
8) start putty again. Actual result: Unable to open connection to COM.... Unable to open serial port. That's while the port is available in the Device Manager.
Expected result: I would expect putty to establish a new connection

the only way to get putty connected again is to reset stm32f4discovery one more time, which is pretty confusing.

This is not a putty issue because originally I've experienced this with my own application which was talking to my MCU using COM port.