HOWTO Set up a Digitiser with GRASS GIS


This is a draft document which gives general advice on how to set up a digitiser under Red Hat Linux. References are given at the end which are of use in elaborating on the process, and in other Unix variants.


1./ Edit the /etc/gettydefs file. Here we define the characteristics of the device and set the protocols for communication by the serial port with the processor and kernel of the operating system..

Each entry is separated by an empty line. The fields isn /etc/gettydefs are

label# initial flags# final flags# login prompt# next label


Quoting Frisch 1995: " The label is used to refer to the entry on the getty command. The initial flags and the final flags are set on the device during the periods before and after login is executed (or initialisation by v.digit, in our case), respectively. Commonly used flags are

                Bn Baud rate of n baud

                CLOCAL Local direcly connected line

                HUPCL Hang up on close

             SANE Set various parameters to reasonable values.


The next label field indicates which label should be used if a break is received on the line. It is designed to enable cycling through various baud rates on dial up lines. If the next label is the same as label no cycling occurs...."


An example of an entry in /etc/gettydefs would be:

# Kurta digitiser on serial port 2 entry

9600# B9600 CLOCAL SANE HUPCL 9600#


2./ Edit /etc/inittab to enable the serial port to start a communication process:

The serial lines in Linux are labelled ttySn where n is the number of the port. Port numbering in Linux starts with 0, so serial port 2 in DOS/Windows is ttyS1.

David Hine    (14. April 1999)

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