User’s Manual
Kara BACnet Gateway
Page 9
3.1 Dip Switch
The four keys DIP switch is used to configure serial port interface for Port 1. Key 1 and 2 are used to
configure the RS-232/422/485 mode of serial port P1 and Key3 and Key 4 are connected to GPIO and
they are reserved for the gateway software.
Switch
1
2
3
4
RS-232
ON
ON
RS-422
OFF
ON
RS-485
OFF
OFF
3.2 Serial Ports
The four serial ports use RJ45 connector and the pin assignment are shown as following table.
Pin
RS-232
RS-422
RS-485
1
DSR
---
--
2
RTS
TXD+
Data+
3
GND
GND
GND
4
TXD
TXD-
Data-
5
RXD
RXD+
---
6
DCD
RXD-
---
7
CTS
---
---
8
DTR
---
---
The Names of the serial ports are:
Port 1 = ttyS1
Port 2 = ttyS2
Port 3 = ttyS3
Port 4 = ttyS4
Port 1: RS-232/422/485 (switch selection)
RS-232: RXD,TXD,RTS,CTS,GND
RS-422: TXD+, TXD-,RXD+,RXD-,GND
RS-485: DATA+,DATA-,GND
Port 2: RS-232: RXD, TXD, RTS, CTS, DSR, DTR, DCD, GND
Port 3: RS-232: RXD, TXD, RTS, CTS, GND
Port 4: RS-232: RXD, TXD, RTS, CTS, GND