RS485 Signal Attenuated

Development Boards Arduino
1

Hi,

I have an AST-CAN485 Dev Board. I am trying to read RS485 data bytes from a steering angle sensor.

When I scope the signal from the steering angle sensor without any other RS485 transceivers connected I get a clean signal.

But when I connect the AST-CAN485 Dev Board with termination resistors and program the RS485 receive example in the Arduino IDE, the signal get attenuated.

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With the attenuated signal I’m not able to read the data bytes from the steering angle sensor.

I’ve tried with and without termination resistors and the signal looks the same. Any other things I can try to get it working?

Thanks for your help.

2

What does the soldering look like?
Are the baud settings identical?

3

Hi,

Soldering joints look ok.

The baudrate is 38400 kbps when I measure with a scope.

Also, I have a DTECH USB-to-RS485 converter and I am able to read data from the steering angle sensor when I connect to it. The signal gets slightly attenuated when I connect to the converter.

Sorry about all the screenshots in one pic. I can only post one media file.

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Lastly, even when I connect lines A and B of the steering angle sensor to the AST-CAN485-DEV Board with no power to the dev board, the signal still shows a large attenuation.

Any help getting this working is greatly appreciated.

4

This is a long shot but try cleaning the flux off your solder joints. Sometimes flux can be conductive and cause weird issues like this.