SwitchDebounce.ino

/****************************************************************************************************************************
  SwitchDebounce.ino
  For ESP8266 boards
  Written by Khoi Hoang

  Built by Khoi Hoang https://github.com/khoih-prog/TimerInterrupt_Generic
  Licensed under MIT license
  Licensed under MIT license

  The ESP8266 timers are badly designed, using only 23-bit counter along with maximum 256 prescaler. They're only better than UNO / Mega.
  The ESP8266 has two hardware timers, but timer0 has been used for WiFi and it's not advisable to use. Only timer1 is available.
  The timer1's 23-bit counter terribly can count only up to 8,388,607. So the timer1 maximum interval is very short.
  Using 256 prescaler, maximum timer1 interval is only 26.843542 seconds !!!

  Now with these new 16 ISR-based timers, the maximum interval is practically unlimited (limited only by unsigned long miliseconds)
  The accuracy is nearly perfect compared to software timers. The most important feature is they're ISR-based timers
  Therefore, their executions are not blocked by bad-behaving functions / tasks.
  This important feature is absolutely necessary for mission-critical tasks.
*****************************************************************************************************************************/
/* Notes:
   Special design is necessary to share data between interrupt code and the rest of your program.
   Variables usually need to be "volatile" types. Volatile tells the compiler to avoid optimizations that assume
   variable can not spontaneously change. Because your function may change variables while your program is using them,
   the compiler needs this hint. But volatile alone is often not enough.

   When accessing shared variables, usually interrupts must be disabled. Even with volatile,
   if the interrupt changes a multi-byte variable between a sequence of instructions, it can be read incorrectly.
   If your data is multiple variables, such as an array and a count, usually interrupts need to be disabled
   or the entire sequence of your code which accesses the data.

   Switch Debouncing uses high frequency hardware timer 50Hz == 20ms) to measure the time from the SW is pressed,
   debouncing time is 100ms => SW is considered pressed if timer count is > 5, then call / flag SW is pressed
   When the SW is released, timer will count (debounce) until more than 50ms until consider SW is released.
   We can set to flag or call a function whenever SW is pressed more than certain predetermined time, even before
   SW is released.
*/
#if !defined(ESP8266)
  #error This code is designed to run on ESP8266 and ESP8266-based boards! Please check your Tools->Board setting.
#endif

// These define's must be placed at the beginning before #include "TimerInterrupt_Generic.h"
// _TIMERINTERRUPT_LOGLEVEL_ from 0 to 4
// Don't define _TIMERINTERRUPT_LOGLEVEL_ > 0. Only for special ISR debugging only. Can hang the system.
#define TIMER_INTERRUPT_DEBUG         1
#define _TIMERINTERRUPT_LOGLEVEL_     0

#include "TimerInterrupt_Generic.h"

#define PIN_D1            5         // Pin D1 mapped to pin GPIO5 of ESP8266

unsigned int SWPin = PIN_D1;

#define TIMER_INTERVAL_MS         20
#define DEBOUNCING_INTERVAL_MS    100
#define LONG_PRESS_INTERVAL_MS    5000

//#define LOCAL_DEBUG               1

// Init ESP8266 timer 1
ESP8266Timer ITimer;

volatile bool SWPressed     = false;
volatile bool SWLongPressed = false;

void IRAM_ATTR TimerHandler()
{
  static unsigned int debounceCountSWPressed  = 0;
  static unsigned int debounceCountSWReleased = 0;

#if (TIMER_INTERRUPT_DEBUG > 0)
  static unsigned long SWPressedTime;
  static unsigned long SWReleasedTime;

  static unsigned long currentMillis;
#endif

  currentMillis = millis();

  if ( (!digitalRead(SWPin)) )
  {
    // Start debouncing counting debounceCountSWPressed and clear debounceCountSWReleased
    debounceCountSWReleased = 0;

    if (++debounceCountSWPressed >= DEBOUNCING_INTERVAL_MS / TIMER_INTERVAL_MS)
    {
      // Call and flag SWPressed
      if (!SWPressed)
      {
#if (TIMER_INTERRUPT_DEBUG > 0)
        SWPressedTime = currentMillis;
        
        Serial.print("SW Press, from millis() = "); Serial.println(SWPressedTime - DEBOUNCING_INTERVAL_MS);
#endif

        SWPressed = true;
        // Do something for SWPressed here in ISR
        // But it's better to use outside software timer to do your job instead of inside ISR
        //Your_Response_To_Press();
      }

      if (debounceCountSWPressed >= LONG_PRESS_INTERVAL_MS / TIMER_INTERVAL_MS)
      {
        // Call and flag SWLongPressed
        if (!SWLongPressed)
        {
#if (TIMER_INTERRUPT_DEBUG > 0)
          Serial.print("SW Long Pressed, total time ms = "); Serial.print(currentMillis);
          Serial.print(" - "); Serial.print(SWPressedTime - DEBOUNCING_INTERVAL_MS);
          Serial.print(" = "); Serial.println(currentMillis - SWPressedTime + DEBOUNCING_INTERVAL_MS);       
#endif

          SWLongPressed = true;
          // Do something for SWLongPressed here in ISR
          // But it's better to use outside software timer to do your job instead of inside ISR
          //Your_Response_To_Long_Press();
        }
      }
    }
  }
  else
  {
    // Start debouncing counting debounceCountSWReleased and clear debounceCountSWPressed
    if ( SWPressed && (++debounceCountSWReleased >= DEBOUNCING_INTERVAL_MS / TIMER_INTERVAL_MS))
    {
      // Call and flag SWPressed
#if (TIMER_INTERRUPT_DEBUGEBUG > 0)
      SWReleasedTime = millis();

      // Call and flag SWPressed
      Serial.print("SW Released, from millis() = "); Serial.println(millis());
#endif

      SWPressed     = false;
      SWLongPressed = false;

      // Do something for !SWPressed here in ISR
      // But it's better to use outside software timer to do your job instead of inside ISR
      //Your_Response_To_Release();

      // Call and flag SWPressed
#if (TIMER_INTERRUPT_DEBUG > 0)
      Serial.print("SW Pressed total time ms = "); Serial.println(millis() - SWPressedTime);
#endif

      debounceCountSWPressed = 0;
    }
  }
}

void setup()
{
  pinMode(SWPin, INPUT_PULLUP);
  
  Serial.begin(115200);
  while (!Serial);
  
  delay(200);

  Serial.print(F("\nStarting SwitchDebounce on ")); Serial.println(ARDUINO_BOARD);
  Serial.println(ESP8266_TIMER_INTERRUPT_VERSION);
  Serial.println(TIMER_INTERRUPT_GENERIC_VERSION);
  Serial.print(F("CPU Frequency = ")); Serial.print(F_CPU / 1000000); Serial.println(F(" MHz"));

  // Interval in microsecs
  if (ITimer.attachInterruptInterval(TIMER_INTERVAL_MS * 1000, TimerHandler))
  {
    Serial.print(F("Starting ITimer OK, millis() = ")); Serial.println(millis());
  }
  else
    Serial.println(F("Can't set ITimer. Select another freq. or timer"));
}

void loop()
{

}