Unable to control serial DTR line

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Hi

I'm trying to control the RTS and DTR lines on the XDA serial port to control a port multiplexer. I can successfully control RTS with EscapeCommFunction( handle, SETRTS ), but the corresponding EscapeCommFunction( handle, SETDTR) doesn't set the DTR line.

When I try the same code compiled for the desktop it controls both lines perfectly.

Does anyone know if the DTR line is implemented by the XDA hardware? It's present on the port as documented on XDA-Developers.

Or could it be that the driver doesn't implement the call properly? If so, it should really return an error code.

The DSR line is not correctly implemented, either in hardware or software as you have identified.