Hi,
I made a MAX485 module with the schematics below...
Everything was working OK when 2 nodes were connected, can Rx or Tx between the master/slave nodes on the Arduino Nano.
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I have tried using 20K pull-up/down at A,B or even no pull-up/down on A,B, same results.
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I tried with 120R termination or 1K R termination, same results.
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Was running at the lowest speed of 9600, same results.
I'm using just very short Cat 5E twisted pair cables during the tests..
I can visually see it is not working as the Rx,Tx LED becomes very dim or not litted at all..
Any idea why does it drop the voltages when 3 or 4th nodes was connected ??
Thank you for reading this..
[url=http://[](MAX485-sch | MAX485 schematics | stanley_seow | Flickr)MAX485-sch
When running on 2 nodes, everything was ok.
[url=http://[](MAX485-2nodes | stanley_seow | Flickr)MAX485-2nodes
When connected n power up the 3rd node, voltages dropped below 2V
[url=http://[](MAX485-3nodes | stanley_seow | Flickr)MAX485-3nodes
Here is a picture of my setup with the newly made PCB..
[url=http://[](MAX485-Eduboard | stanley_seow | Flickr)MAX485-Eduboard