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communication distance, if in a long-distance communication, please reduce the baud
rate, to reduce the signal during transmission by external electromagnetic interference,
please use twisted-pair shielded cable as a communication cable.
RS485 bus in the case of no trunk to support a maximum of 32 nodes, node and
node between the "Daisy chain" connection mode, in the communication cable at both
ends need to add terminal resistance, the resistance value is required to be
approximately equal to the transmission cable characteristic impedance. In short
distance transmission, no final resistance is required, that is, no final resistance is
generally required below 300 meters. The final resistance is connected at the ends of
the transmission cable.
RS485 9 pin definition:
Pin
Name
Function
Remark
1
Data-/B-/485-
Send
positive
Must
connect
2
Data+/A+/485+
Receiving
positive
Must
connect
5
GND
Ground
wire
The RS485 communication wiring diagram is shown in the figure: