The LED matrix is connected to the Raspberry Pi SPI bus via peripheral header. Depending on Raspberry Pi model you can use SPI0 or SPI1 device and chip selects CE0 - CE2. Please note that SPI is disabled in the operating system by default, must be enabled in raspi-config.

The LED matrix can be powered from separate 5V rail. However on later Raspberry Pi models (2,3) it can be powered from the pins 2 and 4 on the P1 header. GND can be connected to any GND pin on P1 header.

LED matrix	Function	GPIO	Pin	Device
DATA	MOSI	GPIO10	19
CLK	SCLK	GPIO11	23
CS	CE0 CE1	GPIO08 GPIO07	24 26	/dev/spidev0.0 /dev/spidev0.1
GND	GND		6,9,14,20,25,30,34,39
5V	+5V		2,4

LED matrix	Function	GPIO	Pin	Device
DATA	MOSI	GPIO20	38
CLK	SCLK	GPIO21	40
CS	CE0 CE1 CE2	GPIO18 GPIO17 GPIO16	12 11 36	/dev/spidev1.0 /dev/spidev1.1 /dev/spidev1.2

Arduino is connected to the Raspberry Pi via USB cable and the communication is serial over USB. The uvled program opens by default /dev/ttyUSB0 virtual serial port.

uvled is a simple command line tool to control MAX7219 based LED matrix panels connected to Raspberry Pi. It requires spi_bcm2708 linux driver to access SPI bus. The application:

• can do exposure of text or png bitmap on LED panel for specified time
• can control grbl xy gantry to move the LED panel
• create png bitmaps from fonts and text

Please check uvled command line syntax.

The source code will be available on github after some required consolidation.