Remarks

Max7219
Status
Source code	GitHub
Datasheet(s)	GitHub
NuGet package

The MAX7219 is an LED display driver capable of driving 64 outputs. As well, the MAX7219 contains an 2-wire data bus allowing multiple MAX7219 chip to be connected together and controlled by a single I2C interface.

Although the MAX7219 can be used as a general purpose IO expander, it almost exclusively used to drive either 2-dimensional LED arrays (commonly 8x8) or an array of multi-segment displays (commonly 8 7-segment displays). The MAX7219 contains specific logic to display pre-configured characters when driving 7 segment displays, specifically: 0-9, E, H, L, P and -.

As it's most commonly used to as a display controller, you'll find it in the Meadow.Foundation.Displays namespace.

Code Example

Max7219 display;

public override Task Initialize()
{
    Resolver.Log.Info("Initialize...");

    display = new Max7219(Device, Device.CreateSpiBus(), Device.Pins.D01, 1, Max7219.Max7219Mode.Character);

    return base.Initialize();
}

void TestCharacterMode()
{
    display.SetMode(Max7219.Max7219Mode.Character);
    //show every supported character 
    for (int i = 0; i < (int)Max7219.CharacterType.Count; i++)
    {
        for (int digit = 0; digit < 8; digit++)
        {
            display.SetCharacter((Max7219.CharacterType)i, digit, i % 2 == 0);
        }
        display.Show();
    }
}

void TestDigitalMode()
{
    Resolver.Log.Info("Digital test");

    display.SetMode(Max7219.Max7219Mode.Digital);
    //control indivial LEDs - for 8x8 matrix configurations - use the Meadow graphics library
    for (byte i = 0; i < 64; i++)
    {
        for (int d = 0; d < 8; d++)
        {
            display.SetDigit(i, d);
        }
        display.Show();
    }
}

public override Task Run()
{
    while (true)
    {
        TestDigitalMode();
        TestCharacterMode();
    }
}

Sample project(s) available on GitHub

Wiring Example

To wire a Max7219 to your Meadow board, connect the following:

Characteristic	Locus
Inheritance	System.Object > Max7219
Implements	IGraphicsDisplay
Namespace	Meadow.Foundation.Displays
Assembly	Max7219.dll

Syntax

public class Max7219 : IPixelBuffer, IGraphicsDisplay

Constructors

Max7219(IMeadowDevice, ISpiBus, IPin, Int32, Max7219.Max7219Mode)

Create a new Max7219 object

Declaration

public Max7219(IMeadowDevice device, ISpiBus spiBus, IPin chipSelectPin, int deviceCount = 1, Max7219.Max7219Mode maxMode = Max7219.Max7219Mode.Display)

Parameters

Type	Name	Description
IMeadowDevice	device	IMeadowDevice
ISpiBus	spiBus	SPI bus
IPin	chipSelectPin	Chip select pin
System.Int32	deviceCount	Number of cascaded devices
Max7219.Max7219Mode	maxMode	Display mode of max7219

Max7219(IMeadowDevice, ISpiBus, IPin, Int32, Int32, Max7219.Max7219Mode)

Create a new Max7219 object

Declaration

public Max7219(IMeadowDevice device, ISpiBus spiBus, IPin chipSelectPin, int deviceRows = 1, int deviceColumns = 1, Max7219.Max7219Mode maxMode = Max7219.Max7219Mode.Display)

Parameters

Type	Name	Description
IMeadowDevice	device	IMeadowDevice
ISpiBus	spiBus	SPI bus
IPin	chipSelectPin	Chip select pin
System.Int32	deviceRows	Number of devices cascaded vertically
System.Int32	deviceColumns	Number of devices cascaded horizontally
Max7219.Max7219Mode	maxMode	Display mode of max7219

Max7219(ISpiBus, IDigitalOutputPort, Int32, Max7219.Max7219Mode)

Create a new Max7219 object

Declaration

public Max7219(ISpiBus spiBus, IDigitalOutputPort chipselectPort, int deviceCount = 1, Max7219.Max7219Mode maxMode = Max7219.Max7219Mode.Display)

Parameters

Type	Name	Description
ISpiBus	spiBus	SPI bus
IDigitalOutputPort	chipselectPort	Chip select port
System.Int32	deviceCount	Number of cascaded devices
Max7219.Max7219Mode	maxMode	Display mode of max7219

Max7219(ISpiBus, IDigitalOutputPort, Int32, Int32, Max7219.Max7219Mode)

Create a new Max7219 object

Declaration

public Max7219(ISpiBus spiBus, IDigitalOutputPort chipselectPort, int deviceRows, int deviceColumns, Max7219.Max7219Mode maxMode = Max7219.Max7219Mode.Display)

Parameters

Type	Name	Description
ISpiBus	spiBus	SPI bus
IDigitalOutputPort	chipselectPort	Chip select port
System.Int32	deviceRows	Number of devices cascaded vertically
System.Int32	deviceColumns	Number of devices cascaded horizontally
Max7219.Max7219Mode	maxMode	Display mode of max7219

Fields

DefaultSpiBusSpeed

MAX7219 Spi Clock Frequency

Declaration

public static Frequency DefaultSpiBusSpeed

Field Value

Type	Description
Frequency

DigitsPerDevice

Number of digits per Module

Declaration

public const int DigitsPerDevice = null

Field Value

Type	Description
System.Int32

Properties

BitDepth

The bit depth of the display

Declaration

public int BitDepth { get; }

Property Value

Type	Description
System.Int32

Buffer

The backing buffer for the pixel buffer (not implemented)

Declaration

public byte[] Buffer { get; }

Property Value

Type	Description
System.Byte[]

ByteCount

The total bytes used for the display buffer

Declaration

public int ByteCount { get; }

Property Value

Type	Description
System.Int32

ColorMode

Color mode of display - 1bpp

Declaration

public ColorMode ColorMode { get; }

Property Value

Type	Description
ColorMode

DeviceCount

Number of cascaded devices

Declaration

public int DeviceCount { get; }

Property Value

Type	Description
System.Int32

DigitColumns

Number of columns when representing digits

Declaration

public int DigitColumns { get; }

Property Value

Type	Description
System.Int32

DigitRows

Number of rows when representing digits

Declaration

public int DigitRows { get; }

Property Value

Type	Description
System.Int32

Height

Height of array of displays in pixels

Declaration

public int Height { get; }

Property Value

Type	Description
System.Int32

Length

Gets the total number of digits (cascaded devices * num digits)

Declaration

public int Length { get; }

Property Value

Type	Description
System.Int32

PixelBuffer

The offscreen buffer used for the display

Declaration

public IPixelBuffer PixelBuffer { get; }

Property Value

Type	Description
IPixelBuffer

SupportedColorModes

The Color mode supported by the display

Declaration

public ColorMode SupportedColorModes { get; }

Property Value

Type	Description
ColorMode

Width

Width of array of displays in pixels

Declaration

public int Width { get; }

Property Value

Type	Description
System.Int32

Methods

Clear()

Clear the display buffer

Declaration

public void Clear()

Clear(Boolean)

Clears the buffer from the given start to end and flushes

Declaration

public void Clear(bool updateDisplay = false)

Parameters

Type	Name	Description
System.Boolean	updateDisplay

Clear(Int32, Int32)

Clears the buffer from the given start to end (exclusive) and flushes

Declaration

public void Clear(int start, int end)

Parameters

Type	Name	Description
System.Int32	start
System.Int32	end

DrawPixel(Int32, Int32, Color)

Draw pixel at location

Declaration

public void DrawPixel(int x, int y, Color color)

Parameters

Type	Name	Description
System.Int32	x	x position
System.Int32	y	y position
Color	color	color of pixel - converted to on/off

DrawPixel(Int32, Int32, Boolean)

Draw pixel at location

Declaration

public void DrawPixel(int x, int y, bool enabled)

Parameters

Type	Name	Description
System.Int32	x	x position in pixels
System.Int32	y	y position in pixels
System.Boolean	enabled	True = turn on pixel, false = turn off pixel

Fill(Color)

Fill the display with a normalized color to on/off

Declaration

public void Fill(Color color)

Parameters

Type	Name	Description
Color	color	The color to fill

Fill(Color, Boolean)

Fill with color

Declaration

public void Fill(Color fillColor, bool updateDisplay = false)

Parameters

Type	Name	Description
Color	fillColor	color - converted to on/off
System.Boolean	updateDisplay	should refresh display

Fill(Int32, Int32, Int32, Int32, Color)

Fill region with color

Declaration

public void Fill(int x, int y, int width, int height, Color fillColor)

Parameters

Type	Name	Description
System.Int32	x	x position
System.Int32	y	y position
System.Int32	width	width of region
System.Int32	height	height of region
Color	fillColor	color - converted to on/off

GetCharacter(Int32, Int32)

Get the stored character

Declaration

public Max7219.CharacterType GetCharacter(int digit, int deviceId = 0)

Parameters

Type	Name	Description
System.Int32	digit	the digit index of the character
System.Int32	deviceId	the cascaded device id

Returns

Type	Description
Max7219.CharacterType

GetDigit(Int32, Int32)

Get the number at a specific position

Declaration

public int GetDigit(int digit, int deviceId = 0)

Parameters

Type	Name	Description
System.Int32	digit	the digit index
System.Int32	deviceId	the cascaded device id

Returns

Type	Description
System.Int32

GetPixel(Int32, Int32)

Get the Color of the pixel at a location (not implemented)

Declaration

public Color GetPixel(int x, int y)

Parameters

Type	Name	Description
System.Int32	x	The x position in pixels
System.Int32	y	The y position in pixels

Returns

Type	Description
Color	The pixel color

InvertPixel(Int32, Int32)

Invert pixel at location (toggle on/off)

Declaration

public void InvertPixel(int x, int y)

Parameters

Type	Name	Description
System.Int32	x	x position in pixels
System.Int32	y	y position in pixels

SetBrightness(Int32)

Sets the brightness of all cascaded devices to the same intensity level.

Declaration

public void SetBrightness(int intensity)

Parameters

Type	Name	Description
System.Int32	intensity	intensity level ranging from 0..15.

SetBrightness(Int32, Int32)

Sets the brightness for a specific device

Declaration

public void SetBrightness(int intensity, int deviceId)

Parameters

Type	Name	Description
System.Int32	intensity	intensity level ranging from 0..15.
System.Int32	deviceId	index of cascaded device.

SetCharacter(Max7219.CharacterType, Int32, Boolean, Int32)

Set a single character

Declaration

public void SetCharacter(Max7219.CharacterType character, int digit, bool showDecimal = false, int deviceId = 0)

Parameters

Type	Name	Description
Max7219.CharacterType	character	the chracter to display
System.Int32	digit	the digit index starting from the left
System.Boolean	showDecimal	show the decimal with the character
System.Int32	deviceId	the cascaded device id

SetDigit(Byte, Int32, Int32)

Set a number at a specific position

Declaration

public void SetDigit(byte value, int digit, int deviceId = 0)

Parameters

Type	Name	Description
System.Byte	value	the value to display
System.Int32	digit	the digit index
System.Int32	deviceId	the cascaded device id

SetMode(Max7219.Max7219Mode)

Set the display mode of the max7219

Declaration

public void SetMode(Max7219.Max7219Mode maxMode)

Parameters

Type	Name	Description
Max7219.Max7219Mode	maxMode	the mode

SetNumber(Int32, Int32)

Set number to display (left aligned)

Declaration

public void SetNumber(int value, int deviceId = 0)

Parameters

Type	Name	Description
System.Int32	value	the number to display
System.Int32	deviceId	the cascaded device id

SetPixel(Int32, Int32, Color)

Set a pixel at a specific location

Declaration

public void SetPixel(int x, int y, Color color)

Parameters

Type	Name	Description
System.Int32	x	The x position in pixels
System.Int32	y	The y position in pixels
Color	color	The pixel color normalized to on/off

Show()

Writes all the Values to the devices.

Declaration

public void Show()

Show(Int32, Int32, Int32, Int32)

Partial screen update

Declaration

public void Show(int left, int top, int right, int bottom)

Parameters

Type	Name	Description
System.Int32	left
System.Int32	top
System.Int32	right
System.Int32	bottom

TestDisplay(TimeSpan)

Helper test method - will turn all leds on then off

Declaration

public void TestDisplay(TimeSpan time)

Parameters

Type	Name	Description
TimeSpan	time	time to show leds

WriteBuffer(Byte[,])

Writes a two dimensional buffer containing all the values to the devices.

Declaration

public void WriteBuffer(byte[, ] buffer)

Parameters

Type	Name	Description
System.Byte[,]	buffer

WriteBuffer(Int32, Int32, IPixelBuffer)

Draw buffer at location

Declaration

public void WriteBuffer(int x, int y, IPixelBuffer displayBuffer)

Parameters

Type	Name	Description
System.Int32	x	x position in pixels
System.Int32	y	y position in pixels
IPixelBuffer	displayBuffer	buffer to draw