Meadow.Foundation.Displays.Max7219

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.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 individual 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:

Class Max7219

Max7219 LED matrix driver

Assembly: Max7219.dll

View Source

Declaration

public class Max7219 : ISpiPeripheral, IDisposable, IPixelDisplay, IDisplay, IPixelBuffer

Implements:
Meadow.Hardware.ISpiPeripheral, System.IDisposable, Meadow.Peripherals.Displays.IPixelDisplay, Meadow.Peripherals.Displays.IDisplay, Meadow.Peripherals.Displays.IPixelBuffer

Properties

DeviceCount

Number of cascaded devices

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Declaration

public int DeviceCount { get; }

DigitRows

Number of rows when representing digits

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Declaration

public int DigitRows { get; }

DigitColumns

Number of columns when representing digits

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Declaration

public int DigitColumns { get; }

Length

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

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Declaration

public int Length { get; }

DefaultSpiBusSpeed

The default SPI bus speed for the device

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Declaration

public Frequency DefaultSpiBusSpeed { get; }

SpiBusSpeed

The SPI bus speed for the device

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Declaration

public Frequency SpiBusSpeed { get; set; }

DefaultSpiBusMode

The default SPI bus mode for the device

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Declaration

public SpiClockConfiguration.Mode DefaultSpiBusMode { get; }

SpiBusMode

The SPI bus mode for the device

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Declaration

public SpiClockConfiguration.Mode SpiBusMode { get; set; }

IsDisposed

Is the object disposed

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Declaration

public bool IsDisposed { get; }

ColorMode

The currently set color mode for the display

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Declaration

public ColorMode ColorMode { get; }

SupportedColorModes

The Color mode supported by the display

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Declaration

public ColorMode SupportedColorModes { get; }

Width

Width of the display in pixels

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Declaration

public int Width { get; }

Height

Height of the display in pixels

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Declaration

public int Height { get; }

PixelBuffer

Provide a buffer that matches this display's color depth, height, and width This should be the buffer that is sent to the device when Show is called

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Declaration

public IPixelBuffer PixelBuffer { get; }

BitDepth

The bit depth of the display

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Declaration

public int BitDepth { get; }

ByteCount

The total bytes used for the display buffer

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Declaration

public int ByteCount { get; }

Buffer

The backing buffer for the pixel buffer (not implemented)

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Declaration

public byte[] Buffer { get; }

Fields

DigitsPerDevice

Number of digits per Module

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Declaration

public const int DigitsPerDevice = 8

spiComms

SPI Communication bus used to communicate with the peripheral

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Declaration

protected ISpiCommunications spiComms

Methods

SetNumber(int, int)

Set number to display (left aligned)

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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

Exceptions

System.ArgumentOutOfRangeException

SetCharacter(CharacterType, int, bool, int)

Set a single character

View Source

Declaration

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

Parameters

Type	Name	Description
Meadow.Foundation.Displays.Max7219.CharacterType	character	the character 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

GetCharacter(int, int)

Get the stored character

View Source

Declaration

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

Returns

Meadow.Foundation.Displays.Max7219.CharacterType

Parameters

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

TestDisplay(TimeSpan)

Helper test method - will turn all leds on then off

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Declaration

public void TestDisplay(TimeSpan time)

Parameters

Type	Name	Description
System.TimeSpan	time	time to show leds

SetMode(Max7219Mode)

Set the display mode of the Max7219

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Declaration

public void SetMode(Max7219.Max7219Mode maxMode)

Parameters

Type	Name	Description
Meadow.Foundation.Displays.Max7219.Max7219Mode	maxMode	the mode

SetBrightness(int, int)

Sets the brightness for a specific device

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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.

SetBrightness(int)

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

View Source

Declaration

public void SetBrightness(int intensity)

Parameters

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

SetDigit(byte, int, int)

Set a number at a specific position

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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

GetDigit(int, int)

Get the number at a specific position

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Declaration

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

Returns

System.Int32

Parameters

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

Show()

Writes all the Values to the devices.

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Declaration

public void Show()

WriteBuffer(byte[,])

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

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Declaration

public void WriteBuffer(byte[,] buffer)

Parameters

Type	Name
System.Byte[,]	buffer

Clear(int, int)

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

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Declaration

public void Clear(int start, int end)

Parameters

Type	Name
System.Int32	start
System.Int32	end

Dispose()

Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.

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Declaration

public void Dispose()

Dispose(bool)

Dispose of the object

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Declaration

protected virtual void Dispose(bool disposing)

Parameters

Type	Name	Description
System.Boolean	disposing	Is disposing

Show(int, int, int, int)

Partial screen update

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Declaration

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

Parameters

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

Clear()

Clear the display buffer

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Declaration

public void Clear()

Clear(bool)

Clears the buffer from the given start to end and flushes

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Declaration

public void Clear(bool updateDisplay = false)

Parameters

Type	Name
System.Boolean	updateDisplay

DrawPixel(int, int, Color)

Draw pixel at location

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Declaration

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

Parameters

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

DrawPixel(int, int, bool)

Draw pixel at location

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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

InvertPixel(int, int)

Invert pixel at location (toggle on/off)

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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

Fill(Color, bool)

Fill with color

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Declaration

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

Parameters

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

Fill(int, int, int, int, Color)

Fill region with color

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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
Meadow.Color	fillColor	color - converted to on/off

WriteBuffer(int, int, IPixelBuffer)

Draw buffer at location

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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
Meadow.Peripherals.Displays.IPixelBuffer	displayBuffer	buffer to draw

Fill(Color)

Fill the display with a normalized color to on/off

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Declaration

public void Fill(Color color)

Parameters

Type	Name	Description
Meadow.Color	color	The color to fill

GetPixel(int, int)

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

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Declaration

public Color GetPixel(int x, int y)

Returns

Meadow.Color: The pixel color

Parameters

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

Exceptions

System.NotImplementedException

SetPixel(int, int, Color)

Set a pixel at a specific location

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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
Meadow.Color	color	The pixel color normalized to on/off

Implements

• Meadow.Hardware.ISpiPeripheral
• System.IDisposable
• Meadow.Peripherals.Displays.IPixelDisplay
• Meadow.Peripherals.Displays.IDisplay
• Meadow.Peripherals.Displays.IPixelBuffer