Remarks

MAX7219
Status
Source code	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

public class MeadowApp : App<F7Micro, MeadowApp>
{
    Max7219 display;

    public MeadowApp()
    {
        Init();

        while(true)
        {
            TestDigitalMode();
            TestCharacterMode();
            CharacterDemo();
        }
    }

    void CharacterDemo()
    {
        display.SetMode(true);
        display.ClearAll();

        for (int i = 0; i < 8; i++)
        {
            display.SetCharacter(Max7219.CharacterType.Blank, i);
        }

        for (int i = 980; i < 999; i++)
        {
            display.SetNumber(i);
            display.Show();
        }

        display.SetCharacter(Max7219.CharacterType.Hyphen, 0);
        display.SetCharacter(Max7219.CharacterType.Hyphen, 1);
        display.SetCharacter(Max7219.CharacterType.P, 2);
        display.SetCharacter(Max7219.CharacterType.L, 3);
        display.SetCharacter(Max7219.CharacterType.E, 4);
        display.SetCharacter(Max7219.CharacterType.H, 5);
        display.SetCharacter(Max7219.CharacterType.Hyphen, 6);
        display.SetCharacter(Max7219.CharacterType.Hyphen, 7);
        display.Show();

        Thread.Sleep(1000);
    }

    void TestCharacterMode()
    {
        display.SetMode(true);

        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();
            Console.WriteLine(((Max7219.CharacterType)i).ToString());
        }
    }

    void TestDigitalMode()
    {
        display.SetMode(false);

        for (byte i = 0; i < 64; i++)
        {
            for(int d = 0; d < 8; d++)
            {
                display.SetDigit(i, d);
            }
            display.Show();
        }
    }

    public void Init()
    {
        Console.WriteLine("Init...");

        display = new Max7219(Device, Device.CreateSpiBus(), Device.Pins.D02, 1, true);
    }
}

Sample projects available on GitHub

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

Syntax

public class Max7219 : DisplayBase

Constructors

Max7219(IIODevice, ISpiBus, IPin, Int32, Max7219.Max7219Type)

Declaration

public Max7219(IIODevice device, ISpiBus spiBus, IPin csPin, int deviceCount = 1, Max7219.Max7219Type maxMode = Max7219.Max7219Type.Display)

Parameters

Type	Name	Description
IIODevice	device
ISpiBus	spiBus
IPin	csPin
System.Int32	deviceCount
Max7219.Max7219Type	maxMode

Max7219(IIODevice, ISpiBus, IPin, Int32, Int32, Max7219.Max7219Type)

Creates a Max7219 Device given a to communicate over and the number of devices that are cascaded.

Declaration

public Max7219(IIODevice device, ISpiBus spiBus, IPin csPin, int deviceRows = 1, int deviceColumns = 1, Max7219.Max7219Type maxMode = Max7219.Max7219Type.Display)

Parameters

Type	Name	Description
IIODevice	device
ISpiBus	spiBus
IPin	csPin
System.Int32	deviceRows
System.Int32	deviceColumns
Max7219.Max7219Type	maxMode

Max7219(ISpiBus, IDigitalOutputPort, Int32, Max7219.Max7219Type)

Declaration

public Max7219(ISpiBus spiBus, IDigitalOutputPort csPort, int deviceCount = 1, Max7219.Max7219Type maxMode = Max7219.Max7219Type.Display)

Parameters

Type	Name	Description
ISpiBus	spiBus
IDigitalOutputPort	csPort
System.Int32	deviceCount
Max7219.Max7219Type	maxMode

Max7219(ISpiBus, IDigitalOutputPort, Int32, Int32, Max7219.Max7219Type)

Declaration

public Max7219(ISpiBus spiBus, IDigitalOutputPort csPort, int deviceRows, int deviceColumns, Max7219.Max7219Type maxMode = Max7219.Max7219Type.Display)

Parameters

Type	Name	Description
ISpiBus	spiBus
IDigitalOutputPort	csPort
System.Int32	deviceRows
System.Int32	deviceColumns
Max7219.Max7219Type	maxMode

Fields

NumDigits

Number of digits Register per Module

Declaration

public const int NumDigits = 8

Field Value

Type	Description
System.Int32

Properties

ColorMode

Declaration

public override DisplayColorMode ColorMode { get; }

Property Value

Type	Description
DisplayColorMode

DeviceColumns

Declaration

public int DeviceColumns { get; }

Property Value

Type	Description
System.Int32

DeviceCount

Number of cascaded devices

Declaration

public int DeviceCount { get; }

Property Value

Type	Description
System.Int32

DeviceRows

Declaration

public int DeviceRows { get; }

Property Value

Type	Description
System.Int32

Height

Declaration

public override uint Height { get; }

Property Value

Type	Description
System.UInt32

Length

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

Declaration

public int Length { get; }

Property Value

Type	Description
System.Int32

SpiClockFrequency

MAX7219 Spi Clock Frequency

Declaration

public static int SpiClockFrequency { get; }

Property Value

Type	Description
System.Int32

Width

Declaration

public override uint Width { get; }

Property Value

Type	Description
System.UInt32

Methods

Clear(Boolean)

Clears the buffer from the given start to end and flushes

Declaration

public override 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

DrawBitmap(Int32, Int32, Int32, Int32, Byte[], BitmapMode)

Declaration

public override void DrawBitmap(int x, int y, int width, int height, byte[] bitmap, BitmapMode bitmapMode)

Parameters

Type	Name	Description
System.Int32	x
System.Int32	y
System.Int32	width
System.Int32	height
System.Byte[]	bitmap
BitmapMode	bitmapMode

DrawBitmap(Int32, Int32, Int32, Int32, Byte[], Color)

Declaration

public override void DrawBitmap(int x, int y, int width, int height, byte[] bitmap, Color color)

Parameters

Type	Name	Description
System.Int32	x
System.Int32	y
System.Int32	width
System.Int32	height
System.Byte[]	bitmap
Color	color

DrawPixel(Int32, Int32)

Declaration

public override void DrawPixel(int x, int y)

Parameters

Type	Name	Description
System.Int32	x
System.Int32	y

DrawPixel(Int32, Int32, Color)

Declaration

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

Parameters

Type	Name	Description
System.Int32	x
System.Int32	y
Color	color

DrawPixel(Int32, Int32, Boolean)

Declaration

public override void DrawPixel(int x, int y, bool colored)

Parameters

Type	Name	Description
System.Int32	x
System.Int32	y
System.Boolean	colored

GetCharacter(Int32, Int32)

Declaration

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

Parameters

Type	Name	Description
System.Int32	digit
System.Int32	deviceId

Returns

Type	Description
Max7219.CharacterType

GetDigit(Int32, Int32)

Declaration

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

Parameters

Type	Name	Description
System.Int32	digit
System.Int32	deviceId

Returns

Type	Description
System.Byte

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.

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

Declaration

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

Parameters

Type	Name	Description
Max7219.CharacterType	character
System.Int32	digit
System.Boolean	showDecimal
System.Int32	deviceId

SetDigit(Byte, Int32, Int32)

Declaration

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

Parameters

Type	Name	Description
System.Byte	value
System.Int32	digit
System.Int32	deviceId

SetMode(Max7219.Max7219Type)

Declaration

public void SetMode(Max7219.Max7219Type maxMode)

Parameters

Type	Name	Description
Max7219.Max7219Type	maxMode

SetNumber(Int32, Int32)

Declaration

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

Parameters

Type	Name	Description
System.Int32	value
System.Int32	deviceId

SetPenColor(Color)

Declaration

public override void SetPenColor(Color pen)

Parameters

Type	Name	Description
Color	pen

Show()

Writes all the Values to the devices.

Declaration

public override void Show()

TestDisplay(Int32)

Declaration

public void TestDisplay(int timeInMs = 1000)

Parameters

Type	Name	Description
System.Int32	timeInMs

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