Restarting a serial port

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I am using a USB serial port in C#. The .net serial port read/write operations work well except in some infrequent cases. If I halt the serial read operations -- as in the case of a debugger break operation -- the serial port seems to hang up. Even if I restart the .exe, the serial port no longer reads data.

I can get it restarted in one of two ways: 1) unplugging and re-plugging the USB serial cable or 2) manually going in to the Device Manager and doing a "disable" and then "enable". In either cases, the serial port begins to read the data properly again. This seems to suggest the problem is not at the serial data transmitter.

I am aware that I can use DevCon to do the disable/enable operations in software. However, this seems a Klutzy way of solving this problem.

Any ideas appreciated.

What I have tried:

I have tried to clear the InBuffer and OutBuffer for the port but this has no effect.

Posted 11-Nov-18 7:14am

Member 10020245

Updated 13-Nov-18 7:34am

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User 11060979 · Answer 1 · 2018-11-11T07:28:00

Solution 1

Usbser.sys still seems to be buggy. A workaround for debugging can be, to connect your device via a usb hub.
See also the discussion here: Checking whether usbser.sys is still working/polling a COM port/CDC device[^]

Posted 11-Nov-18 7:28am

User 11060979

Member 10020245 · Answer 2 · 2018-11-13T07:34:00

After a bit of further experimenting, I found a purely software solution to re-starting the stuck USB serial port. The solution of 1) manually doing a disable/enable in the Device Manager and 2) manually unplugginh/replugging the USB cable was not suitable for operational use -- I need a purely software solution w/o user interventiion. I attempted to use the DevCon to do the disable/enable -- however, on my computer, the results were that the devcon disable step required a reboot in order to finish. This was also deemed not suitable for operations because of the time to do the computer reboot

Finally, I attempted to use devcon's restart procedure. This seems to do the trick. So now I always do a restart after I detect the presence of the serial port device. This takes a negligible amount of time - but always seems to start a stuck USB serial port.

Does anyone have any idea as to what is actually going on here?