frame based button thing, inspired by the quake 3 input code

buttons.cpp

#include <Arduino.h>
#include "buttons.h"

struct buttonState buttonState[2];

void buttonsBegin()
{
  uint8_t buttons = sizeof(buttonState) / sizeof(buttonState[0]);

  for(int i = 0; i < buttons; i++)
  {
    pinMode(buttonState[i].arduinoPin, INPUT);

    buttonState[i].changeTime = millis();
    /* can't meaningfully catch the first 'frame', but technically it's not pressed */
    buttonState[i].currentState = digitalRead(buttonState[i].arduinoPin);
    buttonState[i].changeState = 0;
  }
}

void updateButtons()
{
  uint8_t buttons = sizeof(buttonState) / sizeof(buttonState[0]);

  for(int i = 0; i < buttons; i++)
  {
    uint8_t newState = digitalRead(buttonState[i].arduinoPin);

    if(newState == buttonState[i].changeState)
    {
      buttonState[i].currentState = newState;
    } else {
      buttonState[i].changeTime = millis();
      buttonState[i].changeState = newState;
    }
  }
}

/* debouncing would use time in Pressed / Release if needed */
uint8_t buttonPressed(uint8_t idx)
{
  if(buttonState[idx].currentState == 0 && buttonState[idx].changeState == 1)
    return 1;

  return 0;
}

/* time aspect to holding, where down and up only happen in one 'frame' */
uint8_t buttonHeld(uint8_t idx, uint16_t time)
{
  if(buttonState[idx].currentState == 1)
  {
    if(millis() - buttonState[idx].changeTime >= time)
    {
      /* 'time' ends up being a key repeat rate, need per button data to latch */
      buttonState[idx].changeTime = millis();
      return 1;
    }
  }

  return 0;
}

uint8_t buttonReleased(uint8_t idx)
{
  if(buttonState[idx].currentState == 1 && buttonState[idx].changeState == 0)
    return 1;

  return 0;
}

buttons.h

#include <stdint.h>

enum { BTN_DO, BTN_NEXT };

/*  make this a library, it's just the quake input code thing for 'half presses'
    it's also a nice way to debounce inputs without delays/rereads/filtering */

struct buttonState {
  uint8_t arduinoPin; /* the thing to digitalRead/pinMode */
  int32_t changeTime; /* millis() when state latched */
  uint8_t currentState;
  uint8_t changeState; 
};

extern struct buttonState buttonState[2];

void buttonsBegin();
void updateButtons();

/* debouncing would use time in Pressed / Release if needed */
uint8_t buttonPressed(uint8_t idx);

/* time aspect to holding, where down and up only happen in one 'frame' */
uint8_t buttonHeld(uint8_t idx, uint16_t time = 0);
uint8_t buttonReleased(uint8_t idx);

usage.txt

at the moment buttons are added explicitly, can be nicer as a library

in setup:
buttonState[BTN_DO].arduinoPin = BTN_PIN1;
buttonState[BTN_NEXT].arduinoPin = BTN_PIN2;
buttonsBegin();

in loop:
updateButtons();

if(buttonHeld(BTN_DO, 1000)) /* been held for 1000 milliseconds */
if(buttonPressed(BTN_NEXT)) /* pressed, only triggers once, in the same 'frame' updateButtons just read */