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Raspberry Pi and SPI 8x8 LED matrix example with Java and Pi4j

2020-02-01 10:20:11
This is an example application from my book Getting started with Java on the Raspberry Pi.
There is a lot more info about this topic and other code examples in the book!
You can buy it on Leanpub and will receive all future updates!

THIS IS JUST A SNEAK PEAK!
While looking for a cheap and nice component to demonstrate the use of SPI (Serial Peripheral Interface) I found out this 8x8 matrix LED display on a board with a MAX7219 chip is the perfect piece of hardware!

What you see in the video is the end result with:
  • All on/off
  • Demo of all the lines
  • Demo of all the columns
  • 5 random generated matrixes
  • A set of images including an attempt of the Raspberry Pi logo
  • A, B, E, S, T fixed
  • The same characters scrolling one-by-one


Wiring


As we are using SPI, the number of connections to be made is very minimal:



Code


The sources can be found as an example project within all the sources from the book on GitHub.

The characters and images are created by converting the bit series to byte values inside enums. The number of available definitions is limited as this example is only a demonstration of what you can do, not a fully finished project. So some fun work left for you!

By using the "Find" function in the IDE for value "1" it becomes pretty clear how the defined columns and rows will end up on the matrix display.



Conclusion


You can find these components for a few dollars on eBay and they are great fun to experiment!