RM868500A Operating Manual Page 3
1.1 RS485/RS422 Communications (RS485/RS422 Models only)
The RM868500A includes an on-board termination resistor which can be selected by linking J1 on the main PCB inside
the unit. The termination resistor is 120 Ohms.
1.2 RSSI (Received Signal Strength Indicator) Red LEDS
3 LED’s on: Very strong signal (>30db fade margin)
2 LED’s on: Strong Signal (>20db fade margin)
1 LED on:
Moderate Signal (>10db fade margin)
0 LED’s on: Weak Signal (<10db fade margin)
1.3 Minimum connection required for the RM868500A
Power (ALL models)
: (8->30V DC), Ground
RS232
: TXD,RXD, Ground
RS485
: D+ (B), D- (A)
RS422
: TXD+ (B), TXD- (A), RXD+ (B), RXD- (A)
2 Network Setup
2.1 Frequency Channel Selection
The RM868500A operates on a single channel (869.525MHz) in the SRD G3 Band.
2.2 Network configuration
Network ID:
The RM868500 modems must have the same Network ID to communicate. The network ID can be set using
the free configuration software.
Unicast Mode:
Unicast mode is the only mode that supports retries. While in this mode, receiving modules send an ACK
(acknowledge) of RF packet reception to the transmitter. If the transmitter does not receive an ACK, it will try to resend
the packet up to 3 times. For 2 modems to communicate with each other, the destination address of the transmitting
modem must match the serial number of the receiving modem. The Destination address low is the lower 8 bytes of the
source radio modems serial number, and the destination address high is the upper 8 bytes of the source radio modems
serial number
eg. Unicast Network configuration:
Parameter
RF Modem 1
RF Modem 2
Serial Number
13A2004031D13B
13A200403A0F81
Destination address high
0x0013A200
0x0013A200
Destination address low
0x403A0F81
0x4031D13B
Broadcast Mode (Default):
Any RF modem in range will accept a packet that contains a broadcast address. In this mode
receiving modems do not send ACK’s and transmitting modems do not automatically resend packets as in the case of
unicast mode.
Broadcast Network configuration (All modems in the network must be setup as):
Destination Low Address: 0x0000FFFF
Destination High Address: 0x00000000
