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Use the DigitalInOut interface as a bidirectional digital pin:

  • Read the value of a digital pin when set as an input().
  • Write the value when set as an output().

You can use any of the numbered Arm Mbed pins as a DigitalInOut.

Note: Some boards have a time delay when switching between input and output.

DigitalInOut class reference

Public Member Functions
 DigitalInOut (PinName pin)
 Create a DigitalInOut connected to the specified pin. More...
 DigitalInOut (PinName pin, PinDirection direction, PinMode mode, int value)
 Create a DigitalInOut connected to the specified pin. More...
void write (int value)
 Set the output, specified as 0 or 1 (int) More...
int read ()
 Return the output setting, represented as 0 or 1 (int) More...
void output ()
 Set as an output. More...
void input ()
 Set as an input. More...
void mode (PinMode pull)
 Set the input pin mode. More...
int is_connected ()
 Return the output setting, represented as 0 or 1 (int) More...
DigitalInOutoperator= (int value)
 A shorthand for write() More...
DigitalInOutoperator= (DigitalInOut &rhs)
 A shorthand for write() using the assignment operator which copies the state from the DigitalInOut argument. More...
 operator int ()
 A shorthand for read() More...

DigitalInOut hello, world

 * Copyright (c) 2006-2020 Arm Limited and affiliates.
 * SPDX-License-Identifier: Apache-2.0

#include "mbed.h"

DigitalInOut mypin(LED1);

int main()
    // check that mypin object is initialized and connected to a pin
    if (mypin.is_connected()) {
        printf("mypin is initialized and connected!\n\r");

    // Optional: set mode as PullUp/PullDown/PullNone/OpenDrain

    while (1) {
        // write to pin as output
        mypin = !mypin; // toggle output

        // read from pin as input
        printf("mypin.read() = %d \n\r", mypin.read());

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