RS232 to RS485 converter | RS485 to RS232 converter

This page describes RS232 to RS485 converter and RS485 to RS232 converter.

RS232 to RS485 converter

RS232 to RS485 converter

Figure-1 depicts simple RS232 to RS485 converter. It converts RS232 signal levels to RS485 signal levels. 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 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). Following table-2 mentions RS485 side pin descriptions and signal designations.

RS485 Pin Descriptions
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 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 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 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)

Refer difference between RS232,RS422 and RS485 for more information.

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