Posts: 1
Joined: Thu Mar 06, 2008 9:25 am
Location: USA

Parity Issues

Thu Mar 06, 2008 9:36 am

I am writing some embedded com routines under windows ce 5.0 for one of my boards. The franson tools seem to work nicely to a point, when I noticed an odd problem. Transmission and recption to the main board is 8 bit, Space Parity. I can decode the strings sent perfectly. What I needed to do was transmit to the board using 9th bit set (Mark parity) on the last byte, this lets the processors down the line know the byte transmitted was the last byte. So I thought, I would end the stream (wait a period of time to make sure the transmission was made), disable the com port, reset the parity to mark, enable the serial port and send the last byte. What I realized in the code, was that I never reset the parity to space, yet the reception was still perfect. I then investigated a little further and found that playing with the parity had no effect on the reception, the reception of bytes was perfect (Magic). By the way setting the last byte to mark parity had no effect on the processors down the line, so I do have a problem sending the data. So what gives here???? I have worked with a number of 3rd party serial tools, unfortunately this tool seems to have no changing of the com port setting on the fly, no register interface to the uart and no way of telling what is actually left in the transmit buffer.

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