Knowledgebase

Issue:

How to convert RS422 to RS232 for testing. Applies to the Perle IOLAN+ and Jetstream.

Solution:

This converter is not a substitute for a true RS422 to RS232 converter. RS422 uses a balanced pair to produce signal changes and also has lower voltage specifications than RS232.
It is advised to obtain the proper converter for use in a production environment.

The converter pinouts have been provided for emergency purposes in order to access an RS422 unit using an RS232 terminal to reset or configure the unit.

Before you begin take note that most adapters use the same colored wires for the following pin locations. However you should verify your adapter before using this color scheme.

RJ45 color
1 Blue
2 orange
3 Black
4 Red
5 green
6 yellow
7 Brown
8 white or grey

RS422 to RS232 cable diagrams


RJ45 RS422 DB9 PC RS232
2 SG (orange) ---------------------- 5 SG
3 RXD - (black) -------------------- 3 TXD
4 TXD - (red) ----------------------- 2 RXD
6 RXD + (yellow) ------------------ 5 SG
Loop 4 DTR to 6 DSR and 7 RTS to 8 CTS


RJ45 RS422 DB25 RS232
2 SG (orange) ----------------- 7 SG
3 RXD - (black) ---------------- 2 TXD
4 TXD - (red) ------------------- 3 RXD
6 RXD + (yellow) --------------- 7 SG

Note: length will have a limitation of up to approx 75 feet. Check manufacturer's cabling specs.

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RS422 Pin specs for the Perle IOLAN+ and Jetstream


Perle IOLAN+ (RS422 models only).

1 - No connection
2 - Signal Ground
3 - RXD - RDA Input ( <-- )
4 - TXD - TDA Output ( --> )
5 - TXD+ TDB Output ( --> )
6 - RXD+ RDB Input ( <-- )
7 - No connection
8 - Signal Ground



Perle Jetstream (RS422 models only).

1 - RTS Input ( <-- )
2 - Signal Ground
3 - RXD - RDA Input ( <-- )
4 - TXD - TDA Output ( --> )
5 - TXD+ TDB Output ( --> )
6 - RXD+ RDB Input ( <-- )
7 - CTS Output ( --> )
8 - Signal Ground

Note: The Jetstream RS422 port provides hardware flow control signals (CTS/RTS) at RS232 levels. Ensure that the device you are connecting supports hardware flow control at RS232 voltage levels.

Note: The IOLAN+ and the Jetstream use a common ground. Be sure to use at least one of the signal grounds.