Troubleshooting DeviceMaster LT: NS-Link Linux Installations

Review the following information before calling Technical Support because they will request that you perform many of the procedures or verifications before they will be able to help you diagnose a problem.

You can use the following subsections to test the serial ports on a Linux system.


Pepperl+Fuchs Comtrol, Inc. has available lcom(1), which is a multi-port serial I/O test program. You can use lcom in test mode to send test data to any serial port.


For assistance using lcom, use the manual page (lcom.1) that accompanies the program.

The following examples use ports ttySI0 and ttySI1. You may need to substitute the port numbers that you will be testing.

Hardware TypePort Nomenclature

DeviceMaster 500

DeviceMaster AIR

DeviceMaster LT

DeviceMaster PRO

DeviceMaster RTS

DeviceMaster Serial Hub



Where x is the port number, which begins at 0 (zero) and continues sequentially. Linux is case-sensitive, be sure to use the proper case. tty is lowercase and SI is in uppercase.

You can also refer to the procedures below to check the ports:

File Transfer

You can transfer a file using the following information. The default settings are 9600, 8, n, 1, and no parity. To send a file you can redirect output to a device, where x is 0 through 7, for example:

cat /etc/inittab > /dev/ttySI0

Sends the contents of the /etc/inittab file to the ttySI0 device at 9600 baud, 8, n, 1, and no parity.

Changing Serial Port Settings (stty)

Use the following information if you need assistance changing or viewing the baud rate settings.

To change the baud rate, use the following example, which changes the baud rate to 19200, where x is 0 through 7.

stty 19200 </dev/ttySI0

To view the current serial port settings for ttySI0, enter:

stty -a </dev/ttySI0

Settings changes via stty are only valid during current log in session. For permanent setting changes, use the /etc/inittab file.

Setting Up Terminals and Modems (mgetty, agetty, getty)

Add the appropriate line or lines to the /etc/inittab file then restart.

Some distributions use the agetty command and other distributions use getty. Check the documentation for your Linux distribution if you are unsure.

Terminal Example:

T0:23:respawn:/sbin/agetty -L ttySI0 57600 vt100

Modem Example:

T1:23:respawn:+/sbin/mgetty -m ‘"" AT&F OK’ -D -x9 -s 115200 ttySI0

If necessary, see the manual pages for more information on mgetty.

Testing with minicom

You can also use minicom, which is shipped with most Linux operating systems, to test the serial ports. A Pepperl+Fuchs Comtrol, Inc. document is available for using minicom.

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