Serial Port Settings Explained: Baud Rate, Parity, Stop Bits, and Flow Control

Baud rate

The baud rate controls communication speed. Common values include 9600, 19200, 38400, 57600, and 115200. Both sides must agree.

Data bits, parity, and stop bits

Common configurations look like 8N1: 8 data bits, no parity, and 1 stop bit. Some industrial devices use even parity, odd parity, or 2 stop bits.

Flow control

Flow control manages when data can be sent. Hardware options include RTS/CTS and DTR/DSR. Software flow control uses XON/XOFF characters.

Why settings matter in a bridge

In TCP Server mode, the bridge opens the real serial port directly, so the bridge must use the device's correct serial settings. In RFC2217 client mode, the settings may also matter for the remote serial endpoint.

Practical checklist

• Start with the equipment manual's default serial settings.
• Confirm the COM port number in Windows.
• Match baud rate, data bits, parity, stop bits, and flow control.
• Change one setting at a time when troubleshooting.