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readDigitalPin

Read logical value from GPIO input pin

Syntax

pinvalue = readDigitalPin(mypi,pinNumber)

Description

example

pinvalue = readDigitalPin(mypi,pinNumber) returns the logical value of a digital pin.

This method configures an unconfigured pin as a GPIO input.

If the pin is a GPIO output, or if another interface (I2C, Serial, SPI) uses the pin, this method returns an error message.

Examples

Configure Pin as Input and Read Its Value

Configure a GPIO pin as digital input and read its logical value.

Create a connection from MATLAB® to the Raspberry Pi™ board.

mypi = raspi
mypi = 

  Raspi with Properties:

           DeviceAddress: 'raspberrypi-hysdu8X38o'
                    Port: 18725
               BoardName: 'Raspberry
        Pi Model B Rev 2'
           AvailableLEDs: {'led0'}
    AvailableDigitalPins: [4 7 8 9 10 11 14 15 17 18 22 23 24 25 27 30 31]
    AvailableSPIChannels: {}
      AvailableI2CBuses: {'i2c-0'  'i2c-1'}
             I2CBusSpeed: 100000

The AvailableDigitalPins property shows the list of available digital GPIO pins.

Show the location of all the GPIO pins on your device.

showPins(mypi)

Display the AvailableDigitalPins.

mypi.AvailableDigitalPins   
ans =

  Columns 1 through 13

     4  7  8  9  10  11  14  15  17  18  22  23  24

  Columns 14 through 17

    25  27  30  31

Connect your digital device to the first GPIO pin available, for example GPIO 4.

Configure pin GPIO 4 as a digital input.

configurePin(mypi,4,'DigitalInput')

Read the value from pin GPIO 4.

readDigitalPin(mypi,4)
ans =

  1

The logical value of 1 indicates a positive voltage signal on the pin GPIO 4.

Press a Button to Blink an LED

This example shows how to use a button to blink an LED attached to a GPIO pin.

When you press a button, this example rapidly blinks an LED. The button connects from positive voltage to pin 23. Pressing the button closes the circuit, raising the voltage. When readDigitalPin detects the positive voltage, if buttonPressed becomes true. The program toggles the voltages to pin 24 on and off 10 times. Pin 14 connects to an LED, which connects via a resistor to ground.

for ii = 1:100
    buttonPressed = readDigitalPin(mypi,23)
    if buttonPressed
        for jj = 1:10
            writeDigitalPin(mypi,24,1)
            pause(0.05)
            writeDigitalPin(mypi,24,0)
            pause(0.05)
        end
    end
    pause(0.1)
end

Input Arguments

collapse all

Connection to a specific Raspberry Pi hardware board, specified as a raspi object.

GPIO pin number, specified as a scalar. This argument does not accept vectors because the hardware cannot access multiple pins simultaneously.

To get a list of valid pin numbers, enter mypi.AvailableDigitalPins.

Example: 12

Data Types: double

Output Arguments

collapse all

Logical value of the pin, returned as a scalar.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.