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LED Displays (8 x 8 LED Matrix)
The Pieces
8 x 8 Bi-Colour LED Matrix
(common anode)

The Theory & Code
LED Matrix LED Matrix's are great fun, you can create funky patterns, scroll messages, orcreate something entirely bizarre. Sadly controlling one is a tad complicated. But once mastered is easily repeatable. .: A quick refresher on LED control can be found here :.Matrix Wiring Each matrix has 128 LEDs (64 Red & 64 Green) however there is noticeably not 256 leads. Instead the LEDs are wired into a matrix. This matrix has the LED's anodes connected across rows (8pins) then the red and green LED's cathodes attached across columns (8 pins each). To light an LED connect it's rows anode to +5volts, and through a resistor, it's columns cathode to ground. (you cantry this without a micro-controller) Displaying Images (Scanning) Now that we can light any LED we choose it's time to move on to displaying a (small) image. To do this we will use a scan pattern. Inthe example code we define a bitmap image (an array of 8 bytes, each bit representing one LED). Next we scan through this array one byte at a time, displaying one column then the next. If we do thisfast enough (about 1000 times a second) it appears as an image. It sounds complex but if you download the code and play around it should quickly become clear. (play around with the delay times to see theflicker) Example Code .: Code to test your display a test pattern :. .: Code to scroll a message across the display :. More Things to Try DislikeRed? you can switch to green by shifting the column pins from COL-R to COL-G. Using too many Digital pins? Try controlling the display using shift registers (74HC595) or adedicated display chip (MAX7219) ( .: Full Datasheet & Pinout :.

x1 1K ohm Resistor


The Schematic
pin 10 pin...
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