STM32F722ZE VCP breaks serial windows?

[Julian Carneiro]

Posted on July 10, 2018 at 21:18

Hi,

I am using the USB VCP to connect to a PC serial window. I have connected using PuTTY, correctly received messages from the Nucleo, and correctly sent messages to the Nucleo from the window and I could see those in memory where I expected. However, all of a sudden it stopped working. Now, when I connect to COM4 using PuTTY, it fails and says

Unable to open connection to COM4

Unable to configure serial port

In Device Manager, COM4 is there, and is the port for the VCP

When PuTTY stopped working, I switched to TeraTerm, which worked. I could receive messages, and transmit to the device and I could see that they were appearing Nucleo-side. However, now the Serial port drop-down menu in TeraTerm doesn't even show COM4 despite it appearing in the Device Manager.

This leads me to believe that somehow there has been an error in disconnecting on the Nucleo-side. However, chip-wiping, resetting the device, and restarting the debug doesn't fix the problem like it has for some other people.

I'm hoping that someone can help me figure out the issue and find out how to solve it without getting a new serial window program. Thank you!

#virtual-com-port #usb #stm32f7 #vcp #com-port #serial-port #stm32f722ze

[waclawek.jan]

Posted on July 11, 2018 at 10:30

COM port unavailable in applications (terminal programs) while present in Device Manager usually means, that they are already open by some other application.

Some applications like to 'scan' COM ports to find out newly connected ones, making them temporarily unavailable for other programs. They may be as innocent looking as logic analyzer programs or some data loggers. In these cases it may help to restart the terminal program, or to close/reopen the window which offers the COM port selection (every program has a different strategy in finding out the available COM ports).

JW