RFRS232 to RS485 Converter Explained
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This page describes RS232 to RS485 converters and RS485 to RS232 converters.
Figure-1 depicts a simple RS232 to RS485 converter.
It converts RS232 signal levels to RS485 signal levels.
The following table-1 mentions RS232 side pin descriptions and signal designations.
| RS232 Pin Descriptions |
|---|
| 2 (RXD) Receive Data |
| 3 (TXD) Transmit Data |
| 7 (RTS) Request to Send |
| 8 (CTS) Clear to Send |
| VCC supply voltage |
| GND ground supply voltage |
Table-1: RS232 Side Pins
In an RS232 to RS485 converter, RS232 levels are first converted into TTL levels and later TTL levels are converted to RS485 differential output levels. Commonly used ICs are MAX232 (RS232 to TTL) and MAX485 (TTL to RS485).
The following table-2 mentions RS485 side pin descriptions and signal designations.
| RS485 Pin Descriptions |
|---|
| 1 GND |
| 2 CTS+ |
| 3 RTS+ |
| 4 RXD+ |
| 5 RXD- |
| 6 CTS- |
| 7 RTS- |
| 8 TXD+ |
| 9 TXD- |
Table-2: RS485 Side Pins
RS485 to RS232 Converter
The RS485 to RS232 converter does the reverse of the above functionality. It converts RS485 signal levels to RS232 signal levels. The same cable as mentioned above can be used with proper mating connectors.
RS232 is a single-ended interface, unlike RS485 which is a differential interface.
In RS232, data 1 and data 0 are represented as follows:
- Data ‘1’ using -5V min. and -15V max.
- Data ‘0’ using 5V min. 15V max.
In RS485, data ‘1’ and data ‘0’ are represented based on the differential voltage on two lines (A, B) as follows:
- Data ‘1’ using 1.5V max. (B>A)
- Data ‘0’ using 1.5V max. (A>B)
