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RS485 Baud rate

abdelkarim , 11-05-2021, 02:04 AM
Hello there, i have designed a board with RS485 communicatin . i have used the MAX485 IC . My problem is that the communication is working very well when the baud rate is 9600 and when i try to increase it to 115200 for exemple it dosen't work ! .
Please any idea to help me ?
qdrives , 11-06-2021, 10:42 AM
Have you added 120 ohm termination at both ends?
Make sure that the drive enable pin is made low as soon as the last stop bit is transmitted.
abdelkarim, 11-07-2021, 03:52 AM
yes i added the 120 ohm resistor
robertferanec , 11-07-2021, 01:13 AM
how long is the cable?
abdelkarim, 11-07-2021, 03:53 AM
the cable is <1 m
robertferanec , 11-07-2021, 04:02 AM
do two the same devices (e.g. your board talking to your board) talk to each other or are they different devices (e.g. your board talking to a PC)? the problem could be also inaccurate frequency of UART signal
abdelkarim, 11-07-2021, 01:36 PM
my board is talking to a pc
robertferanec , 11-10-2021, 02:58 AM
Did you consider your MCU frequency based on timing accuracy for the UART at 115200?

This is what I mean, here are some examples: https://www.google.com/search?q=mcu+...WGiOLdTofVh-9M
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