Your patience is appreciated
Dear Sirs,
After some tinkering about I am able to switch on LED's on my parallel port via a c program.. However...
If I run the following program:
#include <stdio.h>
#include <dos.h>
#include <stdlib.h>
int main(void)
{
outportb(0x378, 'A');
}
compile it then run the leds change accordingly, then change the character and compile it works
tedious!!
********************************
If I run the following program:
#include <stdio.h>
#include <dos.h>
#include <stdlib.h>
#include <iostream.h>
int main(void)
{
int val;
start: cin >> val;
outportb(0x378,val);
goto start;
}
It compiles correctly, but when I press a key for the val variable, the whole PC shutsdown!!
I think it is something to do with the common ground of the external PSU and the Parallel port ground.
Circuit configuration..
external PSU +5v connected to 8 resistors which power 8 leds, the LED grounds are connected to a ULN2803A.
The eight data pins connected to the inputs of the ULN2803A
The ground of the PSU and the parallel port connected together and to the ground of the ULN2803.
Cheers!