---
name: "serport"
section: "9"
platform: "linux"
package: "linuxcnc-uspace"
version: "1:2.9.4-2+deb13u1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/serport"
---

# serport(9)

Hardware driver for the digital I/O bits of the 8250 and 16550 serial port.

## NAME

serport - Hardware driver for the digital I/O bits of the 8250 and 16550 serial port.

## SYNOPSIS

**loadrt serport io=*addr\[,addr...\]***

The pin numbers refer to the 9-pin serial pinout.  Keep in mind that these ports generally use rs232 voltages, not 0/5V signals.

Specify the I/O address of the serial ports using the module parameter **io=***addr\[,addr...\]*.  These ports must not be in use by the kernel. To free up the I/O ports after bootup, install setserial and execute a command like:

sudo setserial /dev/ttyS0 uart none

but it is best to ensure that the serial port is never used or configured by the Linux kernel by setting a kernel commandline parameter or not loading the serial kernel module if it is a modularized driver.

## FUNCTIONS

- **serport.***N***.read**

  - **serport.***N***.write**

  ## PINS

- **serport.*N*.pin-1-in bit out**

  Also called DCD (data carrier detect); pin 8 on the 25-pin serial pinout

- **serport.*N*.pin-6-in bit out**

  Also called DSR (data set ready); pin 6 on the 25-pin serial pinout

- **serport.*N*.pin-8-in bit out**

  Also called CTS (clear to send); pin 5 on the 25-pin serial pinout

- **serport.*N*.pin-9-in bit out**

  Also called RI (ring indicator); pin 22 on the 25-pin serial pinout

- **serport.*N*.pin-1-in-not bit out**

  Inverted version of pin-1-in

- **serport.*N*.pin-6-in-not bit out**

  Inverted version of pin-6-in

- **serport.*N*.pin-8-in-not bit out**

  Inverted version of pin-8-in

- **serport.*N*.pin-9-in-not bit out**

  Inverted version of pin-9-in

- **serport.*N*.pin-3-out bit in**

  Also called TX (transmit data); pin 2 on the 25-pin serial pinout

- **serport.*N*.pin-4-out bit in**

  Also called DTR (data terminal ready); pin 20 on the 25-pin serial pinout

- **serport.*N*.pin-7-out bit in**

  Also called RTS (request to send); pin 4 on the 25-pin serial pinout

## PARAMETERS

- **serport.*N*.pin-3-out-invert bit rw**

  - **serport.*N*.pin-4-out-invert bit rw**

  - **serport.*N*.pin-7-out-invert bit rw**

  - **serport.*N*.ioaddr u32 r**

  ## LICENSE

GPL