Creating a /dev/alpha Device on Linux

Creating the device is as simple as figuring out what serial port you've got the sign hooked up to. For instance, COM1:

    # ln -s /dev/cua0 /dev/alpha

If you are brave, you can give the world read/write access to your sign. This may be important, especially if you are using a web server to update the sign.

    # chmod a+rw /dev/alpha

Configuring the Communication Settings for Binary Access

Commands to the sign use control characters. (See the protocol.)

These settings provide a 9600,E,7,1 connection to the sign for use with the RJ12 to RS232-DB9 adapter.

    $ stty 0:705:1ad:0:3:1c:7f:15:4:0:1:0:11:13:1a:0:12:f:17:16:0:0:73 < /dev/alpha
This is the same as $ stty 9600 -opost -ocrnl -onlcr cs7 parenb -parodd < /dev/alpha

Testing the sign

alphatest.pl
    #!/usr/bin/perl

    # Get the attention of the sign
    print "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";

    # Tell the sign to print the message
    $message = "It Worked!";
    print "\001" . "Z" . "00" . "\002" . "AA" . "\x1B" . " b" . $message . "\004";

Make the code executable and run it, redirecting output to the sign's device:
$ chmod u+x alphatest.pl
$ ./alphatest.pl > /dev/alpha

The sign should now read "It Worked!"

This page last updated [Protcol notes] [ALPHA 215C] [Building a Data Cable] [MindPrint]