Button is giving me the same voltage when pressed or released

Question

I am doing a simple program with my PIC (PIC24FJ1024GB610).

When a button is pressed the LED is turned on, when it is released LED is turned off.

I presumed that the input pins have a pullup resistor connected to it inside the microcontroller by default, because when I measured the voltage across the pin when it was floating, it was 3.3V

^{simulate this circuit – Schematic created using CircuitLab}

In a pull-up configuration, Vinput is 3.3V when the button is released, and 0V when the button is pressed.

However, when the button is pressed or released I measured the same value which is 3.3V

I am using a breadboard to design the circuit, and a pic development board: Explorer16/32

I added the code FYI.

#include "System.h"
#include <xc.h>

/*


 P44 is input RB15
 P88 is output RF1 5V tolerant



 */


#define ANALOG  1
#define DIGITAL 0

#define INPUT   1
#define OUTPUT  0

//BTN RB15
#define BTN_ANS     ANSBbits.ANSB15
#define BTN_TRIS    TRISBbits.TRISB15
#define _INPUT      PORTBbits.RB15

//LED RF1
#define LED_TRIS    TRISFbits.TRISF1
#define _OUTPUT     _LATF1


int main (void)
{
    //LED_ANS = DIGITAL;
    LED_TRIS = OUTPUT;

    _OUTPUT = 0;

    BTN_ANS = DIGITAL;
    BTN_TRIS = INPUT;

    while(1)
    {
        if(_INPUT == 1)
            _OUTPUT = 1;
        else
            _OUTPUT = 0;
    }


    return 0;
}

Answer 1

Buttons rarely make reliably sound electrical contact with breadboards.

Based on comments, that appears to have been your issue, along with possible quality issues in the button itself.

Sometimes there are thing you can go to make something work well enough for a quick test, eg, I had some buttons where twisting each of the pins 90 degrees would make them better fit the breadboard contacts and so work a useful fraction of the time. But really, breadboards are not for reliability, especially not with anything that is not a DIP IC or wire lead component of suitable wire gauge.

You would be better off soldering your button to a circuit board (perhaps a pre-made prototype board), or buying some pre-made assembly of buttons, and wiring that into your MCU board directly.