Question
What is the pinout for the DB9 connector on the Digi TransPort WR31, for both RS232 and RS422/RS485 operation?
Answer
The TransPort WR31 has a single DB9 serial connector. It is a DCE port (default baud rate 115200) that operates as RS232 and, on RS422/RS485-capable units, as RS422/RS485. The pin assignments are:
RS232 pinout
|
Pin
|
Direction
|
Signal
|
Description
|
|
1
|
Out
|
DCD
|
Data Carrier Detect
|
|
2
|
Out
|
RXD
|
Receive Data
|
|
3
|
In
|
TXD
|
Transmit Data
|
|
4
|
In
|
DTR
|
Data Terminal Ready
|
|
5
|
N/A
|
GND
|
Ground
|
|
6
|
Out
|
DSR
|
Data Set Ready
|
|
7
|
In
|
RTS
|
Ready To Send
|
|
8
|
Out
|
CTS
|
Clear To Send
|
|
9
|
Out
|
RI
|
Ring Indicate
|
RS422 / RS485 pinout
|
Pin
|
Direction
|
Signal
|
Description
|
|
1
|
Out
|
CTS-
|
Clear To Send -
|
|
2
|
Out
|
RD+
|
Receive Data +
|
|
3
|
In
|
TD+
|
Transmit Data +
|
|
4
|
In
|
RTS_B
|
Ready To Send -
|
|
5
|
N/A
|
GND
|
Ground
|
|
6
|
Out
|
RD-
|
Receive Data -
|
|
7
|
In
|
RTS+
|
Ready To Send +
|
|
8
|
Out
|
CTS+
|
Clear To Send +
|
|
9
|
In
|
TD-
|
Transmit -
|
For true RS485 2-wire (half-duplex) operation, tie TD+ (pin 3) to RD+ (pin 2) and TD- (pin 9) to RD- (pin 6). The RTS and CTS signals are optional and are not normally needed for RS485.
Reference material
- Digi TransPort® Routers User Guide (part number 90001019) — "TransPort WR31 serial pinout" (RS232 and RS422/RS485 pinout tables)
https://docs.digi.com/resources/documentation/digidocs/pdfs/90001019.pdf
- Digi TransPort WR31 product / model page (DB-9 RS-232/422/485 serial interface)
https://www.digi.com/products/models/wr31-m22a-de1-tb
Last updated:
Jul 28, 2026