Stanislas BertrandIt seems I always struggle with RS232 DB9 pinout. This page is to track it.
A good reference for DB9 can be found in FTDI RS232 Cable. See Datasheet page 17.
The RS232 connector (Male) has the following pinout, i.e configured as a Data Terminal Equipment (DTE).
| Pin | Type | Description |
| 1 | Input | DCD = Data Carrier Detect |
| 2 | Input | RXD = Receive Data |
| 3 | Output | TXD = Transmit Data |
| 4 | Output | DTR = Data Terminal Ready |
| 5 | Ground | GND = RS232 signal ground |
| 6 | Input | DSR = Data Set Ready |
| 7 | Output | RTS = Request To Send |
| 8 | Input | CTS = Clear To Send |
| 9 | Input / Power | RI = Ring Indicator |
The device this adapter connects to should follow the following pinout.
The RS232 device connector is then female, configured as Data Communication Equipment (DCE).
| Pin | Type | Description |
| 1 | Output | DCD = Data Carrier Detect |
| 2 | Output | RXD = Receive Data Aka Device Transmit pin (DT-in/DC-out) |
| 3 | Input | TXD = Transmit Data Aka Device Receive pin (DT-out/DC-in) |
| 4 | Input | DTR = Data Terminal Ready |
| 5 | Ground | GND = RS232 signal ground |
| 6 | Output | DSR = Data Set Ready |
| 7 | Input | RTS = Request To Send (DT-out/DC-in) |
| 8 | Output | CTS = Clear To Send (DT-in/DC-out) |
| 9 | Input / Power | RI = Ring Indicator |
The data flow in summarized as follow.
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