Change_Interval.ino

/****************************************************************************************************************************
  Change_Interval.ino
  For Arduino and Adadruit AVR 328(P) and 32u4 boards
  Written by Khoi Hoang

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

  Now we can use these new 16 ISR-based timers, while consuming only 1 hardware Timer.
  Their independently-selected, 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.
*****************************************************************************************************************************/

/*
   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.
*/

// These define's must be placed at the beginning before #include "TimerInterrupt.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         0
#define _TIMERINTERRUPT_LOGLEVEL_     0

#define USE_TIMER_1     true

#if ( defined(__AVR_ATmega644__) || defined(__AVR_ATmega644A__) || defined(__AVR_ATmega644P__) || defined(__AVR_ATmega644PA__)  || \
        defined(ARDUINO_AVR_UNO) || defined(ARDUINO_AVR_NANO) || defined(ARDUINO_AVR_MINI) ||    defined(ARDUINO_AVR_ETHERNET) || \
        defined(ARDUINO_AVR_FIO) || defined(ARDUINO_AVR_BT)   || defined(ARDUINO_AVR_LILYPAD) || defined(ARDUINO_AVR_PRO)      || \
        defined(ARDUINO_AVR_NG) || defined(ARDUINO_AVR_UNO_WIFI_DEV_ED) || defined(ARDUINO_AVR_DUEMILANOVE) || defined(ARDUINO_AVR_FEATHER328P) || \
        defined(ARDUINO_AVR_METRO) || defined(ARDUINO_AVR_PROTRINKET5) || defined(ARDUINO_AVR_PROTRINKET3) || defined(ARDUINO_AVR_PROTRINKET5FTDI) || \
        defined(ARDUINO_AVR_PROTRINKET3FTDI) )
  #define USE_TIMER_2     true
  #warning Using Timer1, Timer2
#else          
  #define USE_TIMER_3     true
  #warning Using Timer1, Timer3
#endif

// To be included only in main(), .ino with setup() to avoid `Multiple Definitions` Linker Error
#include "TimerInterrupt.h"

#if !defined(LED_BUILTIN)
  #define LED_BUILTIN     13
#endif

#ifndef LED_BLUE
  #define LED_BLUE              7
#endif


#define TIMER1_INTERVAL_MS        100UL
#define TIMER_INTERVAL_MS         200UL

volatile uint32_t Timer1Count = 0;
volatile uint32_t TimerCount  = 0;

void printResult(uint32_t currTime)
{
  Serial.print(F("Time = ")); Serial.print(currTime); 
  Serial.print(F(", Timer1Count = ")); Serial.print(Timer1Count);
  
  Serial.print(F(", TimerCount = ")); Serial.println(TimerCount);
}

void TimerHandler1(void)
{
  static bool toggle1 = false;

  // Flag for checking to be sure ISR is working as Serial.print is not OK here in ISR
  Timer1Count++;

  //timer interrupt toggles pin LED_BUILTIN
  digitalWrite(LED_BUILTIN, toggle1);
  toggle1 = !toggle1;
}

void TimerHandler(void)
{
  static bool toggle = false;

  // Flag for checking to be sure ISR is working as Serial.print is not OK here in ISR
  TimerCount++;
  
  //timer interrupt toggles outputPin
  digitalWrite(LED_BLUE, toggle);
  toggle = !toggle;
}

void setup()
{
  pinMode(LED_BUILTIN, OUTPUT);
  pinMode(LED_BLUE,    OUTPUT);
  
  Serial.begin(115200);
  while (!Serial);

  Serial.print(F("\nStarting Change_Interval on "));
  Serial.println(BOARD_TYPE);
  Serial.println(TIMER_INTERRUPT_VERSION);
  Serial.print(F("CPU Frequency = ")); Serial.print(F_CPU / 1000000); Serial.println(F(" MHz"));

  // Select Timer 1-2 for UNO, 1-5 for MEGA, 1,3,4 for 16u4/32u4
  // Timer 2 is 8-bit timer, only for higher frequency
  // Timer 4 of 16u4 and 32u4 is 8/10-bit timer, only for higher frequency
  ITimer1.init();

  // Using ATmega328 used in UNO => 16MHz CPU clock ,
  // For 16-bit timer 1, 3, 4 and 5, set frequency from 0.2385 to some KHz
  // For 8-bit timer 2 (prescaler up to 1024, set frequency from 61.5Hz to some KHz

  if (ITimer1.attachInterruptInterval(TIMER1_INTERVAL_MS, TimerHandler1))
  {
    Serial.print(F("Starting  ITimer1 OK, millis() = ")); Serial.println(millis());
  }
  else
    Serial.println(F("Can't set ITimer1. Select another freq. or timer"));

#if USE_TIMER_2
  
  ITimer2.init();

  if (ITimer2.attachInterruptInterval(TIMER_INTERVAL_MS, TimerHandler))
  {
    Serial.print(F("Starting  ITimer2 OK, millis() = ")); Serial.println(millis());
  }
  else
    Serial.println(F("Can't set ITimer2. Select another freq. or timer"));

#elif USE_TIMER_3

  ITimer3.init();

  if (ITimer3.attachInterruptInterval(TIMER_INTERVAL_MS, TimerHandler))
  {
    Serial.print(F("Starting  ITimer3 OK, millis() = ")); Serial.println(millis());
  }
  else
    Serial.println(F("Can't set ITimer3. Select another freq. or timer"));

#endif    
}

#define CHECK_INTERVAL_MS     10000L
#define CHANGE_INTERVAL_MS    20000L

void loop()
{
  static uint32_t lastTime = 0;
  static uint32_t lastChangeTime = 0;
  static uint32_t currTime;
  static uint32_t multFactor = 0;

  currTime = millis();

  if (currTime - lastTime > CHECK_INTERVAL_MS)
  {
    printResult(currTime);
    lastTime = currTime;

    if (currTime - lastChangeTime > CHANGE_INTERVAL_MS)
    {
      //setInterval(unsigned long interval, timerCallback callback)
      multFactor = (multFactor + 1) % 2;

      // interval (in ms) and duration (in milliseconds). Duration = 0 or not specified => run indefinitely
      // bool setInterval(unsigned long interval, timer_callback callback, unsigned long duration)
      
      ITimer1.setInterval(TIMER1_INTERVAL_MS * (multFactor + 1), TimerHandler1);

      Serial.print(F("Changing Interval, Timer1 = ")); Serial.println(TIMER1_INTERVAL_MS * (multFactor + 1)); 

#if USE_TIMER_2
      ITimer2.setInterval(TIMER_INTERVAL_MS * (multFactor + 1), TimerHandler);

      Serial.print(F("Changing Interval, Timer2 = ")); Serial.println(TIMER_INTERVAL_MS * (multFactor + 1));  
#elif USE_TIMER_3
      ITimer3.setInterval(TIMER_INTERVAL_MS * (multFactor + 1), TimerHandler);

      Serial.print(F("Changing Interval, Timer3 = ")); Serial.println(TIMER_INTERVAL_MS * (multFactor + 1));                            
#endif
      
      lastChangeTime = currTime;
    }
  }
}