RS232 to RS485 Tranciever
RS232 standard is defined for communications over 50 feet or less. RS485 on the other side can handle up to 4000 feet.
Tranciever converts voltage levels from/to RS232 +-12V available on your PC serial (com) port to RS485 5V level.
Tranciever is not protocol dependent. Set RTS high to enable transmittion on RS485 line.
| RS232 signal(DB9 pin) | Direction | Max232 pin | Direction | Max485 pin | Comment |
| TX(3) | --> | R2in(8) | | | |
| RX(2) | <-- | T2out(7) | | | |
| RTS(8) | --> | R1in(13) | | | RTS will enable RS485 TX |
| Signal GND(5) | | GND(15) | | GND(5) | Signal and Common Ground |
| | | T1in(11) | <-- | RO(1) | |
| | | R1out(12) | --> | DI(4) | |
| | | R2out(9) | --> | 2,3 | Install LEDs on this link to see TX/RX Enabled |
| | | Vcc(16) | | VCC(8) | +5V |
| | | | | A(6) | RS485 Output A |
| | | | | B(7) | RS485 Output B |
Although some converters get power from RS232 port, it is better to use external power supply for long distance terminated connections.
Power can be provided from a 5V voltage regulator mounted on the same board or completely external power supply.
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