How do I check and configure serial ports under Linux for various purposes such as modem, connecting null modems or connect a dumb terminal?
Linux offers various tools. Linux uses ttySx for a serial port device name. For example, COM1 (DOS/Windows name) is ttyS0, COM2 is ttyS1 and so on.
Task: Display Detected System’s Serial Support
Simple run dmesg command
$ dmesg | grep tty
[ 37.531286] serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A [ 37.531841] 00:0b: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A [ 37.532138] 0000:04:00.3: ttyS1 at I/O 0x1020 (irq = 18) is a 16550A
setserial is a program designed to set and/or report the configuration information associated with a serial port. This information includes what I/O port and IRQ a particular serial port is using, and whether or not the break key should be interpreted as the Secure Attention Key, and so on. Just type the following command:
$ setserial -g /dev/ttyS
/dev/ttyS0, UART: 16550A, Port: 0x03f8, IRQ: 4 /dev/ttyS1, UART: 16550A, Port: 0x1020, IRQ: 18 /dev/ttyS2, UART: unknown, Port: 0x03e8, IRQ: 4 /dev/ttyS3, UART: unknown, Port: 0x02e8, IRQ: 3
setserial with -g option help to find out what physical serial ports your Linux box has.
Linux serial console programs
Once serial ports identified you can configure Linux box using various utilities:
- minicom– The best friendly serial communication program for controlling modems and connecting to dump devices
- wvidial or other GUI dial up networking program – a PPP dialer with built-in intelligence.
- getty / agetty – agetty opens a tty port, prompts for a login name and invokes the /bin/login command.
- grub / lilo configuration – To configure serial port as the system console