I need to communicate with a PLC in serial port. PLC sends 4 possible data: 0, 1, 2 or 3 (which are status).
My vb.net program uses IO.Ports.SerialPort class. When I read the data, the "1" and "2" are good, but the "0" and "3" are received as "?". I tried all the Read method (ReadByte, ReadExisting, Read, etc), it always give the same result. In HyperTerminal, it's fine.
I made a test program in another computer (Win 7). Test was perfect, I received all 4 status correctly. I ran the same test program on the original computer (Win XP) and once again, I got the "1" et the "2" but the "0" and the "3" was "?" (ascii 63).
anyone have an idea?? because I'm really puzzled here.
thanks a lot for your time and help