Module michaellee1019:max7219

A Viam module to support various functions of the max7219 chip. The module is a wrapper of the luma.led-matrix python library.

Model michaellee1019:led_matrix:max7219

Provides ability to control the LEDs on many 8x8 dot matrix displays with a max7219 chip. This generic component provides many DoCommand functions to render text, lines, rectangles, and more on the display.

Supported Hardware

• Tested with a 3 pack of EC Buying MAX7219 Dot Matrix Modules

Other hardware may work, but may have different orientation requiring the block_orientation and rotate attributes to be set.

Wiring

The first module should be wired to a raspberry pi in the following way:

Max Pin	RPI Pin
VCC	Any 5v Pin
GND	Any Ground Pin
DIN	MOSI Pin 19 / GPIO 10
CS	CE0 Pin 24 / GPIO 8
CLK	SCLK Pin 23 / GPIO 11

Based on the official pinout diagram provided by Raspberry Pi.

Configuration

The following config is used to control a single HiLetgo MAX7219 Dot Matrix Module

{
    "spi_bus": "<string>",
    "device": "<string>",
    "block_orientation": <int>,
    "width": <int>,
    "height": <int>,
    "rotate": <int>
}

Attributes

The following attributes are available for this model:

Name	Type	Inclusion	Description
spi_bus	int	Required	The SPI bus number.
device	int	Required	The device number.
width	int	Required	The width of the display.
height	int	Required	The height of the display.
block_orientation	int	Optional	Some displays have the individual 8x8 led displays rotated. Use this block_orientation attribute to rotate the individual pixels within the block. Defaults to 0.
rotate	int	Optional	Use this to logically rotate pixel rendering if you have a display that is mounted upside down or vertically. Defaults to 0 which is no rotation (upright horizontal).

Example Configuration

{
    "spi_bus":"0",
    "device":"0",
    "block_orientation": 0,
    "width": 32,
    "height": 24,
    "rotate": 0
}

DoCommand Examples

A single DoCommand call will erase the display and draw a new canvas from scratch. Each DoCommand call can contain a list of drawings to be performed in a single frame, where the screen will not be cleared between each drawing.

Border

Draws a border around the display using the provided width + height in the attributes of the component. This type has no options available to it.

{
    "drawings": [
        {
            "type": "border"
        }
    ]
}

Rectangle

Draw a rectangle on the display. Options:

• pixels: An array of integers representing the start and end pixels to draw the rectangle. Provide the coordinates a list of four integers like [start_x, start_y, end_x, end_y].

{
    "drawings": [
        {
            "type": "rectangle",
            "pixels": [
                0,
                0,
                4,
                5
            ]
        }
    ]
}

Text

Write text to the display. Options:

• message: The text to display
• start_pixel: The xy coordinates to start the text. Helpful to center text visually. Provide the coordinates a list of two integers like [x, y].
• font: The font to use, defaults to LCD_FONT if not provided. The other option is CP437_FONT which provides thicker "bold" letters.

{
    "drawings": [
        {
            "type": "text",
            "message": "VIAM",
            "start_pixel": [
                3,
                0
            ],
            "font": "CP437_FONT"
        }
    ]
}

Point

Light up a single pixel on the display. Options:

• pixel The xy coordinates of the pixel. Provide the coordinates a list of two integers like [x, y].

{
    "drawings": [
        {
            "type": "point",
            "pixel": [
                3,
                0
            ]
        }
    ]
}

Line

Draw a line of pixels on the display. Options:

• pixels: An array of integers representing the start and end pixels to draw the line. Provide the coordinates a list of four integers like [start_x, start_y, end_x, end_y].

{
    "drawings": [
        {
            "type": "line",
            "pixels": [
                0,
                0,
                0,
                5
            ]
        }
    ]
}

Clear

Erases all pixels on the display to show a blank screen.

{
    "drawings": [
        {
            "type": "clear"
        }
    ]
}

Multiple drawings.

Provide a list of drawings to place multiple elements on to the screen. The next DoCommand will erase the screen

{
    "drawings": [
        {
            "type": "point",
            "pixel": [
                0,
                0
            ]
        },
        {
            "type": "text",
            "message": "VIAM",
            "start_pixel": [
                3,
                0
            ]
        },
        {
            "type": "line",
            "pixels": [
                31,
                0,
                31,
                7
            ]
        }
    ]
}