Interfacing a graphic LCD
Pretty Jumper Cables
A few years ago, I purchased a surplus set-top box that was basically just a generic 100Mhz x486 compatible computer that I was going to use as a component in my stereo system to play MP3s, complete with remote and LCD display. I wrote the server-side database (Apache, SQL) and had most of the client-side software written (all in Perl, IIRC.) The last piece of the puzzle was getting the LCD & remote (plus a rotary encoder for good measure) working. I had already found the perfect LCD (from All Electronics, of course); it was the (almost) perfect physical dimensions for my box, and I had already designed some variable-width fonts and planned the functionality of the interface - I just, you know, didn't know how to make it all work. Well, I decided to tackle this last part of functionality.
The secret lives of magstripe cards
I love All Electronics, the Van Nuys, CA retailer that buys surplus electronics inventories and offers them to the public at discount prices. One of the items I acquired through them was an assembly from a credit card verification device - it included a circuit board with various ICs (including a DTMF encoder/decoder that I plan to mess with at some point) and a 2-track magnetic stripe reader manufactured by MagTek, Inc. From the datasheet, the interface seemed relatively straight forward: aside from +5v and ground, there were a strobe (clock) and data line for each track, and a common 'card present' line.
First projects
This post is to get up to speed on the digital projects I've been experimenting with. Over the years, I've collected various components in the hopes that one day I would bring them to life respectively scanning, displaying, or blinking on my desk. My first project, however, was just to get my feet wet with the unit. It read the input from one of the ADC's (analog to digital converters) and display it's estimated value onto 3 LEDs (light emitting diodes.) I mostly used code examples from the Teensy website.