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Author Topic:   F120 UART1
Codedawg
New Member 		posted August 11, 2010 10:26 AM     Click Here to See the Profile for Codedawg     Edit/Delete Message
Anyone ever have trouble with F120 RX on UART1 only at baud rates above 14400? Wondering if it might be something to do with RX sync on TIMER1.

Hoping to heck its not the layout of my board...

Thanks

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erikm
Member 		posted August 11, 2010 10:45 AM     Click Here to See the Profile for erikm   Click Here to Email erikm     Edit/Delete Message
Assuming you are doing it right, using an ISR not a wait loop in main

only at baud rates above 14400?
14k is a fairly low rate to get problems at except at main loops

Wondering if it might be something to do with RX sync on TIMER1.
You do not have T1 doing anything else, I hope.

Hoping to heck its not the layout of my board...
for 14k it would be a mistake, not just a layout issue (unless you have a 1 or 2 layer board with the traces running 4 times around the board before hitting.

My best guess is that you have another ISR that is too lenghty, the check is simple, as a diagnostic means set UART1 ONLY at high priority, if that makes higher baudrates work my best guess is correct

Erik

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Codedawg
New Member 		posted August 11, 2010 11:54 AM     Click Here to See the Profile for Codedawg     Edit/Delete Message
Thanks Eric,

Turned out to be a faulty 232 to 485 converter in my test setup. Replaced it with a quality American made one, all works fine.

Apologies, question withdrawn.

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erikm
Member 		posted August 11, 2010 01:20 PM     Click Here to See the Profile for erikm   Click Here to Email erikm     Edit/Delete Message
Turned out to be a faulty 232 to 485 converter
232-485 converters have a bit of trouble switching direction, more if you go fster. the other way (485-232) is even more tricky, the better ones follow a good way, but must eventually give up.

If at all possible, AVOID 485-232 converters, if you have to use them keep the baudrate 'low'

Erik

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