This project is a working proof of concept, in building an extremely low cost LED display, using simple custom PIC24-based driver and interfacing in real-time with a Linux-based ARM SoC.
The project consist in a crude display driver based on PIC24FJ256GA702 and nothing else, attached to the display's HUB75 connector.
Then, the O.S. passes each frame to the driver via a SPI interface. At the moment, frames are only 64x64 pixels @256 colors [4KiB].
The kernel module uses an available SPI interface. The current implementation
uses SPI2 (hardcoded value) of the
Olimex A20-OLinuXino-LIME,
but can be easily tweaked in the initialization of the structure
spi_device_info in gdpymod.c.
After the module is compiled and inserted into the running kernel, the user
application must open() the device /dev/gdpymod in bw mode and send each
frame with a simple call to write().
Most of the test code is written in Python, for example a low-res and low-colors mirror using a webcam.
