Characteristic	Locus
Inheritance	System.Object > x74595
Inherited Members	System.Object.ToString() System.Object.Equals(System.Object) System.Object.Equals(System.Object, System.Object) System.Object.ReferenceEquals(System.Object, System.Object) System.Object.GetHashCode() System.Object.GetType() System.Object.MemberwiseClone()
Namespace	Meadow.Foundation.ICs.IOExpanders
Assembly	x74595.dll

Syntax

public class x74595

Remarks

Shift registers offer the ability to increase the number of outputs on a microcontroller by using I2C or SPI interfaces. In the case of the 74xx595 series of shift registers, the SPI interface is used to output a series of bits that are then latched to the output pins of the chip.

This class allows Meadow to control the output pins on a 74HCT595 shift register using the SPI interface.

Note that when using this chip care should be taken to make sure that the total output load of the chip does not exceed the current and thermal dissipation properties for the specific shift register being used.

Examples

The application below uses a ShiftRegister74595 object to cycle through the bits on the shift register and light the appropriate LED.

using System.Threading;
using Meadow;
using Meadow.Foundation.ICs.IOExpanders;

namespace x74595_Sample
{
    public class Program
    {
        static IApp _app; 
        public static void Main()
        {
            _app = new App();
        }
    }

    public class App : AppBase<F7Micro, App>
    {
        public App ()
        {
            var config = new SPI.Configuration(SPI_mod: SPI_Devices.SPI1,
                                             ChipSelect_Port: Pins.GPIO_PIN_D8,
                                             ChipSelect_ActiveState: false,
                                             ChipSelect_SetupTime: 0,
                                             ChipSelect_HoldTime: 0,
                                             Clock_IdleState: true,
                                             Clock_Edge: true,
                                             Clock_RateKHz: 10);

           shiftRegister = new x74595(8, config);
           shiftRegister.Clear(true);

           int index = 0;
           while (true)
           {
               shiftRegister[index] = true;
               Thread.Sleep(500);
               shiftRegister[index] = false;
               index = index == 8 ? 0 : index + 1;
           }
        }
    }
}

Example Circuit

Constructors

x74595(ISpiBus, Int32)

Constructor a ShiftRegister74595 object.

Declaration

public x74595(ISpiBus spiBus, int pins)

Parameters

Type	Name	Description
ISpiBus	spiBus	SpiBus object
System.Int32	pins	Number of pins in the shift register (should be a multiple of 8 pins).

Properties

Item[Int32]

Overload the index operator to allow the user to get/set a particular pin in the shift register.

Declaration

public bool this[int pin] { get; set; }

Parameters

Type	Name	Description
System.Int32	pin	Bit number to get/set.

Property Value

Type	Description
System.Boolean	Value in the specified pin.

Methods

Clear(Boolean)

Clear all of the pins in the shift register.

Declaration

public void Clear(bool latch = false)

Parameters

Type	Name	Description
System.Boolean	latch	If true, latch the data after the shift register is cleared (default is false)?

CreateOutputPort(IIODevice, IPin, Boolean)

Creates a new DigitalOutputPort using the specified pin and initial state.

Declaration

public IDigitalOutputPort CreateOutputPort(IIODevice device, IPin pin, bool initialState)

Parameters

Type	Name	Description
IIODevice	device
IPin	pin	The pin number to create the port on.
System.Boolean	initialState	Whether the pin is initially high or low.

Returns

Type	Description
IDigitalOutputPort

IsValidPin(Byte)

Check if the specified pin is valid.

Declaration

protected bool IsValidPin(byte pin)

Parameters

Type	Name	Description
System.Byte	pin	Pin number

Returns

Type	Description
System.Boolean	True if the pin number is valid, false if it not.

LatchData()

Send the data to the SPI interface.

Declaration

protected void LatchData()

WriteToPort(Byte, Boolean)

Sets a particular pin's value.

Declaration

public void WriteToPort(byte pin, bool value)

Parameters

Type	Name	Description
System.Byte	pin	The pin to write to.
System.Boolean	value	The value to write. True for high, false for low.

WriteToPorts(Byte)

Outputs a byte value across all of the pins by writing directly to the shift register.

Declaration

public void WriteToPorts(byte mask)

Parameters

Type	Name	Description
System.Byte	mask