DigitalIn

Hello World!
API
Interface
Related

The DigitalIn interface is used to read the value of a digital input pin.

Any of the numbered mbed pins can be used as a DigitalIn.

Hello World!¶

» Import this program
DigitalIn_HelloWorld_Mbed - main.cpp

#include "mbed.h"
 
DigitalIn enable(p5);
DigitalOut led(LED1);
 
int main() {
    while(1) {
        if(enable) {
            led = !led;
        }
        wait(0.25);
    }
}

» Import this program
DigitalIn_HelloWorld_FRDM-KL25Z - main.cpp

#include "mbed.h"
 
DigitalIn enable(PTB0);
DigitalOut led(LED_BLUE);

int main() {
    while(1) {
        if(enable) {
            led = !led;
        }
        wait(0.25);
    }
}

API¶

API summary

» Import latest build into a program
mbed - DigitalIn Class Reference

Public Member Functions
	DigitalIn (PinName pin)
	Create a DigitalIn connected to the specified pin.
int	read ()
	Read the input, represented as 0 or 1 (int)
void	mode (PinMode pull)
	Set the input pin mode.
	operator int ()
	An operator shorthand for read()

Interface¶

The DigitalIn Interface can be used on any pin with a blue label.

The pin input is logic '0' for any voltage on the pin below 0.8v, and '1' for any voltage above 2.0v. By default, the DigitalIn is setup with an internal pull-down resistor.

/media/uploads/chris/pinout-thumbnails.jpg

See the Pinout page for more details

To handle an interrupt, see InterruptIn

Examples of logical functions

Boolean logic - NOT, AND, OR, XOR

#include "mbed.h"
 
DigitalIn a(p5);
DigitalIn b(p6);
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;
    }
}

Ask a question

Last modified 02 Mar 2013, by Samuel Mokrani. 13 comments

1 related question:

answers

disable pin interrupt

Ian Mellor
3 months, 2 weeks ago

DigitalIn

13 comments:

Dimiter K

# 30 Oct 2010

Last example should have a variable name before (p5), otherwise it gives an error related to the class constructor.

Simon Ford

# 30 Oct 2010

Thanks, fixed.

Alexandre Nunes

# 13 Nov 2010

I can see from the schematics that the LED pins on the ethernet phy are routed to the µC. How can I name those pins so that I can read from them?

Prashant Achari

# 04 Feb 2011

Hi i want to capture the output of serial ADC which generates samples at the rate of 1.25MSPS, can i do it with the mbed ...?

Charles Lee

# 13 Mar 2011

May i Know if i put the push On switch and 1 pin connect to the Mbed pin5 and another pin connect to which Mbed pin?sorry, i am newbie..Thanks

Eric Wertz

# 09 Jun 2011

@Alexandre Nunes - the pins corresponding to the two LEDs for the Ethernet PHY are not addressable using DigitallIn().

Calling Ethernet.link() would be the correct way to see if your PHY has link or not, if that's what you're ultimately trying to determine.

@Prashant Achari

It is probable that you can, but using DigitalIn() may not be the best (or a workable) way to do it. It may also depend on your ADC (the serial protocol, # of bits/sample, # of channels). This would be a question best raised in the forum with more complete information, if you have not done so already.

@Charles Lee

Where to connect the other switch pin to depends on how you want the switch to work (high or low when pressed, and whether or not you are using internal or external pullups). This would also be a good question to ask in the forum.

Eric Wertz

# 09 Jun 2011

What is the default (pullup) mode for a newly constructed DigitalIn()? It would seem like this is something that should be documented explicitly.

ali ali

# 25 Jul 2011

the z_and with z_or should be z_and = a & b; z_or = a | b;

Feliciano Domingos

# 28 Nov 2012

How to use switch button ANDed with internal(embedded) LEDs to command external LEDs? For example:

if(led1==1&sw1==0) led1 is internal or embedded. LEDred7 = 1; external LED.

Thank you in advance.

Christian Lerche

# 28 Nov 2012

Feliciano:

code tags.

if(led1==1&sw1==0) //led1 is internal or embedded. 
LEDred7 = 1; //external

That being said, do you have a whole program?
I would like to see what else you defined in there.

Lerche

Filho Wu

# 05 Dec 2012

How can I just revise and check the pin mode related to pull up, pull down and open drain?

L van der Kolk

# 08 Dec 2012

Hi Mbed team,

I think it would be a good idea to show some code examples here about the possible pinmodes. (PullUp, PullDown) The only thing mentioned here is that there are default pulldown resistors present, but NOT how to change this. Is'nt this the right place for some explanation about this with small examples? I had to search all over the site for more information about this subject. Regards, LvdK

Jose Paul

# 10 Dec 2012

Using enable for the pin is slightly confusing as it can be thought of as enabling the pin as a digital input

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mbed

DigitalIn

Table of Contents

Hello World!¶

» Import this program
DigitalIn_HelloWorld_Mbed - main.cpp

» Import this program
DigitalIn_HelloWorld_FRDM-KL25Z - main.cpp

API¶

» Import latest build into a program
mbed - DigitalIn Class Reference

Public Member Functions

Interface¶

Boolean logic - NOT, AND, OR, XOR

1 related question:

13 comments:

Recent changes

mbed

DigitalIn

Table of Contents

Hello World!¶

» Import this programDigitalIn_HelloWorld_Mbed - main.cpp

» Import this programDigitalIn_HelloWorld_FRDM-KL25Z - main.cpp

API¶

» Import latest build into a programmbed - DigitalIn Class Reference

Public Member Functions

Interface¶

Related¶

Boolean logic - NOT, AND, OR, XOR

1 related question:

13 comments:

Recent changes

» Import this program
DigitalIn_HelloWorld_Mbed - main.cpp

» Import this program
DigitalIn_HelloWorld_FRDM-KL25Z - main.cpp

» Import latest build into a program
mbed - DigitalIn Class Reference