CDC failes after a device reboot

NETMF & Gadgeteer
1

I create a CDC connection over USB (Vitual Comport) and sends data to a terminal program (as an example).

-> USBC_CDC cdc = USBClientController.StandardDevices.StartCDC();
-> cdc.Write(TempBuffer, 0, TempBuffer.Length);

This works fine.

Then I need to reboot my device - if a fatal error shows up.

-> PowerState.RebootDevice(false, 1000);

Under the reboot the ComPort goes away in the Windows Device Manager.
Then it shows up again when the device is running and CDC called again.

BUT, now I get no data in the Terminal program. Even not if the port is closed and reopened.

When I close the Terminal program and restarts it, then I cannot see the ComPort in the selection list.
But, it exists in the device manager!

I have tried with several programs and I see the same problem - the CDC is not working after a device reboot.

Same problem is seen if the USB cable is unplug and repluged.

What goes wrong?

2

Windows is very picky about CDC devices. You can’t reboot while connection is open.

3

Thats is so true…

How to shut down the CDC?

I have found examples on how to open it but not hoe to close it.

4

Just close the related COM port usually does work.

5

Do You mean on the PC side?

But how to close the CDC on the FEZ side?

6

I usually do not need to close it on device side. I do not think it is possible

7

Here is a solution:

The FEZ can reboot faster than Windows can detect a hardware change!

If one makes a 10 sec sleep before calling StartCDC

 Thread.Sleep(10000);
 cdc = USBClientController.StandardDevices.StartCDC();

then windows will act correctly.

If the e.g. gets a power failure, reboot or a hardware watchdog reset this will then work.