Re: UART timing
- From: Uwe Hercksen <hercksen@xxxxxxxxxxxxxxxxxxx>
- Date: Fri, 09 Sep 2005 10:52:00 +0200
Ross Marchant schrieb:
Thanks, I'm trying to solve a problem for someone remotely. Symptoms: * HyperTerminal connection to GPRS modem at 9600 baud works fine. Messages come through fine at server. * Embedded device connection to GPRS modem at 9600 baud doesn't work properly. AT commands have to be sent one byte at a time slowly, and once connected messages sent come out as garbage at server end.
Sounds to me like the embedded device's baud rate is way off, although I am assured its only 1.6%. Maybe the modem is out by 3% and hence the error occurs.
Hello,
there are some microprocessors with built in UART which generate the baudrate clock from a 20 MHz clock. For 9600 Baud, there is an error of + 1 % or - 1,4 %, but this error does not affect the communication.
What about messuring the signals with a scope? Some care is necessary to measure UART signals with a precision better than 1 %.
Bye
.
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- From: Ross Marchant
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