Omega Speaker Systems iLD Series manual Wiring RS485 Interface, Device # with RS485

2.4.1 Wiring RS485 Interface

RS485 interface uses a two-wire communication system (one for transmitting and one for receiving) plus a common wire to connect to the shield of the cable. It is recommended to use a shielded cable with one twisted pair.

Use of twisted pair and shield will significantly improve noise immunity.

Figure 2.3 shows multi-point, half-duplex RS485 interface connections for the iServer.

iLD Big Display TB4	DEVICE #1
	-Tx/-Rx	+Tx/+Rx
1 2 3			GND
			.........................
-Tx/-Rx
+Tx/+Rx

Twisted shielded pair

...............................

-Tx/-Rx +Tx/+Rx GND

DEVICE #29

-Tx/-Rx +Tx/+Rx GND

DEVICE #31

-Tx/-Rx

+Tx/+Rx

GND

120 Ohm

Termination resistor

-Tx/-Rx +Tx/+Rx GND

...............................

DEVICE #2 DEVICE #30

Figure 2.3 Multi-point, Half-Duplex RS485 Wiring

Value of the termination resistor is not critical and depends on the cable impedance.

Table 2.3 shows RS485 half-duplex hookup between the iServer serial port and device with RS485 communication interface.

Table 2.3 Half Duplex Hookup

TB4 Pin#	iLD Big Display	DEVICE # WITH RS485
Pin 2	+Tx/+Rx (+Transmit/+Receive)	+Tx/+Rx (+Transmit/+Receive)
Pin 3	-Tx/-Rx (-Transmit/-Receive)	-Tx/-Rx (-Transmit/-Receive)
Pin 1	RTN (Common GND)	GND (Common GND)

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