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Use the DigitalIn interface to read the value of a digital input pin. The logic level is either 1 or 0.

You can use any of the numbered Arm Mbed pins can be used as a DigitalIn.

DigitalIn class reference

API summary

Public Member Functions
 DigitalIn (PinName pin)
 DigitalIn (PinName pin, PinMode mode)
int read ()
void mode (PinMode pull)
int is_connected ()
 operator int ()
Protected Attributes
gpio_t gpio

DigitalIn hello, world

/* mbed Example Program
 * Copyright (c) 2006-2014 ARM Limited
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *     http://www.apache.org/licenses/LICENSE-2.0
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * See the License for the specific language governing permissions and
 * limitations under the License.
#include "mbed.h"

DigitalIn  mypin(SW2); // change this to the button on your board
DigitalOut myled(LED1);

int main()
    // check mypin object is initialized and connected to a pin
    if(mypin.is_connected()) {
        printf("mypin is connected and initialized! \n\r");
    // Optional: set mode as PullUp/PullDown/PullNone/OpenDrain
    // press the button and see the console / led change
    while(1) {
        printf("mypin has value : %d \n\r", mypin.read());
        myled = mypin; // toggle led based on value of button

DigitalIn example

To handle an interrupt, see InterruptIn.

Examples of logical functions - boolean logic NOT, AND, OR, XOR:

#include "mbed.h"
DigitalIn a(D0);
DigitalIn b(D1);
DigitalOut z_not(LED1);
DigitalOut z_and(LED2);
DigitalOut z_or(LED3);
DigitalOut z_xor(LED4);
int main() {
    while(1) {
        z_not = !a;
        z_and = a && b;
        z_or = a || b;
        z_xor = a ^ b;

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