By Fritz Weinrebe on 05 August 2008

I decided to make a Google SketchUp drawing of the simpit and this is what I came up with:





SketchUp is actually easy to use (and addictive).  I suggest to watch the training videos of Sketchup to make the most out of it.  See Google Sketchup for more details.

By Fritz Weinrebe on 05 August 2008

Driving 7 Segment LEDs from a micro controller is fairly easy, but it uses quite a lot of Port pins on the IC.  But what if you can free up more pins on the micro controller and use a serial device to drive the LED display?

The MAXIM7219 or 7221 is a IC that will do just that. 

The MAX7219 is a compact, serial input/output common-cathode display drivers that interface microprocessors (μPs) to 7-segment numeric LED displays of up to 8 digits, bar-graph displays, or 64 individual LEDs. Included on-chip are a BCD code-B decoder, multiplex scan circuitry, segment and digit drivers, and an 8x8 static RAM that stores each digit.

Only one external resistor is required to set the segment current for all LEDs.

The following is a typical diagram for using this chip. (See www.maxim-ic.com for more details and the datasheet.)
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