New E-Mail Messages Checker with 7-Segment LED
The other night I came across a 7-segment LED display and decided to interface it to a parallel port. I added a button as well. The 7-segment LED lines (each leg of the display plus the dot LEDs) are connected to the parallel port data pins (D0-D7). I have the button hooked up to nInitialize (bidirectional) and nAck (input only). I’ve never done a parallel port interface project before, so I figured this would be a good start.
I wrote some quick prototype software in Perl, of all languages. It requires Device::ParallelPort for parallel port access, which for some reason didn’t work well with writing data bytes, so I had to resort to doing everything bit by bit in software. For the switch, I bring nInitialize down, and poll nAck for changes. When nAck goes low, the switch has been pressed.
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