For testing, & with a known "on frequency" receiver (or transmitter), you should be able to tolerate close to 5% error for a 10 bit charecter. (start, 8 x data, stop). If you use a parity bit this reduces to about 4.5%. Normally, if you allow the same error for the transmiter & receiver then 2.5% is the linmit, reducing to a max of 2% with a safety margin. Personally, I wouldn't go beond 1% unless data loss was correctable or unimportant. But 0.94% should be fine. Note howver that the figures above are based on a maximum 1/2 bit slip over the sent charecter. The receiver sampling method can reduce this toleence band somewhat. Richard P On 03/05/06, Info wrote: > Did some tests today and it worked fine at 38400 baud. > 57600 baud and above failed miserabely. > Used the code that Maestro generates, PIC18F458 at 40 MHz > > 38400 baud: the calculated speed error is 0.16% > 57600 baud: is 0.94% error. > > Is 0.94% too much error?? Or why would it be so terrible result? > (More than 50% of the echoed chrs were random) > > > > I've done 115,200 baud reliably on a 18F452 with a 18.43Mhz crystal > > > using HiTech PICC, all interrupt driven. > > > One thing to check is the accuracy of the frequency division for the > > > UART generator. I figured I could do 115K baud reliable with a 20Mhz > > > crystal (about 3% error), but the EE in charge wanted to have an "exact" > > > frequency division for baud rate accuracy. > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist