CL4790 Hardware Integration Guide
Version 3.0
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10
CONN-HIG_CL4790
RS485
Figure 5: CL4790-RS485
The RS485 interface uses a Differential Data Transmission that can help nullify the effects of ground shifts
and induced noise signals that can appear as common mode voltages on a network.
The CL4790 uses a RS485 (2-wire Half Duplex) multi-drop interface. Typically, a RS485 bus consists of a
master and several slaves. The nodes have unique addresses and can send addressed packets to specific
nodes. Because the bus is half duplex, no two nodes should try to talk at the same time. The CL4790 does
not have a RS485 address; therefore it transmits all RS485 traffic over the RF. Conversely, as soon as the
CL4790 receives a packet over the RF, it transmits the packet over the RS485 bus.
Table 4: CL4790 Terminal Block Pinout
Terminal Block Pin
Signal Name
Description
1
VCC
6-18V (1.3A required)
2
485 -
485B
3
N/C
No Connect
4
N/C
No Connect
5
485 +
485A
6
GND
Ground
Note: When using RS485 (2-wire Half Duplex), a RS485 to RS232 converter is required to configure the unit.
Laird recommends a B&B Electronics 4WSD9R converter to translate RS485 to RS232.
Figure 6: RS232-485 Converter
