This project is about controlling LED matrix displays. It’s about doing the hard work with a microcontroller so that the work left to do on a Raspberry Pi is minimised.
The following diagram represents the system architecture. A Raspberry Pi, on the left, sends text or image data to the display over an SPI interface. The LED controller, in the middle, transforms the display data and generates the control signals required to control the LED matrix display board. The controller then sends the data and control signals over a HUB08 or HUB75 interface to a display on the right. This project is about making the controller, the bit in the middle.
The goal of this project is to make a Pi HAT for LED Matrix displays that supports the HUB08 and HUB75 interface and can drive displays in character or graphical modes. These modes are used to classify the display. Character mode is the simplest. In this mode the Raspberry Pi calls printf style functions with strings of text to write to a display. In graphical mode the Raspberry Pi provides an array of RGB data. Graphical mode will allow you to create static or moving images on the display.
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