Peter Goddard

MSB error at 250K baud with TWR-SER

Discussion created by Peter Goddard on Aug 13, 2012
Latest reply on Aug 14, 2012 by Peter Goddard


     In my quest to get the TWR-SER driven by a TWR-K60N512 I have an intermittent MSB fault. At 115200 baud where the divisors do not divide exactly, the serial comms is fine. When I change the baud rate to 250000 (the rate for DMX512) where the divisors are exact, every 30 characters or so, a '@' = 0x40 is captured as 'À' == 0xC0 on 2 terminal programs. The program prints '@' every second. Unfortunately I do not have an oscilloscope but chose these characters to try to highlight the problem. I am using a USB to serial adaptor because I do not have a traditional RS232 connector on my laptop. As the serial adaptor and TWR-SER card have screw mounts on their connectors and foul each other, I have to use a 3 meter extension cable.


I have tried this with 8 bits, 1 stop bit and no parity and still the problem persists. I know DMX uses 2 stop bits but I'm trying to strip it back to basics. I will then try 9 bit mode and keep the 9th bit permanently high to deputise as the second stop bit.


Any ideas?


Thanks in advance

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