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7. RS485 Communication Interface
About RS485
A typical RS485 connection is as below.
Device 1
Some Noteworthy Points:
1. Wires between devices and computer shall be twisted.
2. Maximum allowable wire length is 1000 meters.
3. The terminal-end device should have a terminal resistor.
4. Due to multiple connections, each individual device should be assigned an
IP address as to send/receive.
RS485 Hardware Interface
Device 2
+ - + - + -
T/R + T/R -
T/R +
T/R -
Device N
Connecting to device or computer with RS485 interface
L3
L2
L1
12
Terminal
Resistor
T/R +
T/R -
RS485 wiring
illustration
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