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 DisplayBase > Max7219
Inherited Members DisplayBase.IgnoreOutOfBoundsPixels
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 DisplayBase.DisplayColorMode ColorMode { get; }

Property Value

Type Description
DisplayBase.DisplayColorMode

Overrides

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 int Height { get; }

Property Value

Type Description
System.Int32

Overrides

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 int Width { get; }

Property Value

Type Description
System.Int32

Overrides

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

Overrides

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)

Declaration
public override void DrawPixel(int x, int y)

Parameters

Type Name Description
System.Int32 x
System.Int32 y

Overrides

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

Overrides

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

Overrides

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

InvertPixel(Int32, Int32)

Declaration
public override void InvertPixel(int x, int y)

Parameters

Type Name Description
System.Int32 x
System.Int32 y

Overrides

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)

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

Overrides

Show()

Writes all the Values to the devices.

Declaration
public override void Show()

Overrides

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