Step 20 : RS485 Output Circuitry
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U1 = RS485 Chip
The RS485 chip in this specific case is the ST485EBN because Phil favors the low power consumption, but others are pin compatible and slightly cheaper.
Compared with the RS485 input protection circuitry, this is completely trivial.
Just get the polarity right.
RJ45 Pin 5 goes to the RS485 chip pin 6, the A or + terminal
RJ45 Pin 4 goes to the RS485 chip pin 7, the B or – terminal.
Once you go through one of these controllers, there is no longer any discussion about RS232. If you used RS232 into this board, it is now RS485 coming out. End of story.
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