THE MAGAZINE FOR COMPUTER APPLICATIONS
Circuit Cellar Online offers articles illustrating creative solutions
and unique applications through complete projects, practical
tutorials, and useful design techniques.

LINUX DRIVES WEEDER I/O BOARDS

by Jack Dennon

Start ý Create the Device Driver ý Create the Device ý The Order of Things ý Load the Device Driver ý Call the Test Program ý Remove the Device Driver ý Sources and PDF

CALL THE TEST PROGRAM

The test program reads the 14-bit digital input on the WTDIO board using the AR command. Pull the least significant bit of this word low by adding a jumper wire from wire terminal A to ground on the WTDIO board. If you make that connection and then call the test program with the command wtdio, you should see a response such as what is shown in Listing 1.

Procopen: filename = com2
Procopen: check for reserved name
file: com2  driver: com_dev
bps = 9600 parity = n nsb = 1 ndb = 8
com2 opened as 3
A3FFE

Most of this output is just diagnostic messages that you can suppress by commenting out the code that creates these lines. The data from the Weeder Technology board is displayed in the last line. The letter A is the address that is set in the dip switches of the Weeder board, and the hex value 3FFE shows that the least significant bit of the 14-bit input is indeed low while the rest are high.