How to find out if my COM port has recieved XOFF?

Asked Jun 02 '16 at 02:58

Active Jun 02 '16 at 02:58

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I am testing code for serial port communication. I am using synchronous IO for now to keep things simple. I have observed that when the PC recieves XOFF the program pauses, no more printing in the console window. When the program recieves XON it starts running again.

What method exists to find out if my program's serial port has earlier recieved XOFF (regardless of synchronous and asynchronous IO) since the COM port driver shall prevent the port from sending any characters out in this case and I better check if XOFF was recieved before calling writefile().

I think that one way is to use the ClearCommError() with COMSTAT struct. Is this the only way? I get this impression by reading https://msdn.microsoft.com/en-us/library/ff802693.aspx If that is so, it certainly appears a strange way of doing that.

asked Jun 02 '16 at 02:58

quantum231

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I didn't think XOFF/XON was handled at a driver level. – Mark Ransom Jun 02 '16 at 03:18
As soon as XOFF is recieved my writefile loop is automatically blocked. This atleast confirms that XOFF impacts something outside my program. Whether it be the driver or something in windows, I do not know. – quantum231 Jun 02 '16 at 03:20
It might help to see some code on how you open and write to the serial port. – Mark Ransom Jun 02 '16 at 03:45
I can't find example for software flow controlled serial communication – quantum231 Jun 02 '16 at 09:30
You should be able to specify no flow control when opening the port then the don xoff will pass through to your application to handle completely. – DisappointedByUnaccountableMod Jun 12 '16 at 13:33

How to find out if my COM port has recieved XOFF?

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