Change_Interval.ino

/****************************************************************************************************************************
  Change_Interval.ino
  For Arduino AVR ATtiny-based boards (ATtiny3217, etc.) using megaTinyCore
  Written by Khoi Hoang

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

  Now with we can use these new 16 ISR-based timers, while consuming only 1 hwarware 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.
*****************************************************************************************************************************/

// Important Note: To use drag-and-drop into CURIOSITY virtual drive if you can program via Arduino IDE
// For example, check https://ww1.microchip.com/downloads/en/DeviceDoc/40002193A.pdf

#if !( defined(MEGATINYCORE) )
  #error This is designed only for MEGATINYCORE megaAVR board! Please check your Tools->Board setting
#endif

// These define's must be placed at the beginning before #include "megaAVR_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

// Select USING_FULL_CLOCK      == true for  20/16MHz to Timer TCBx => shorter timer, but better accuracy
// Select USING_HALF_CLOCK      == true for  10/ 8MHz to Timer TCBx => shorter timer, but better accuracy
// Select USING_250KHZ          == true for 250KHz to Timer TCBx => longer timer,  but worse  accuracy
// Not select for default 250KHz to Timer TCBx => longer timer,  but worse accuracy
#define USING_FULL_CLOCK      true
#define USING_HALF_CLOCK      false
#define USING_250KHZ          false         // Not supported now

// Try to use RTC, TCA0 or TCD0 for millis()
#define USE_TIMER_0           true          // Check if used by millis(), Servo or tone()
#define USE_TIMER_1           false         // Check if used by millis(), Servo or tone()

#if USE_TIMER_0
  #define CurrentTimer   ITimer0
#elif USE_TIMER_1
  #define CurrentTimer   ITimer1
#else
  #error You must select one Timer  
#endif

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

#ifdef LED_BUILTIN
  #undef LED_BUILTIN

  // To modify according to your board
  // For Curiosity Nano ATtiny3217 => PIN_PA3
  #if defined(ARDUINO_AVR_CuriosityNano3217) 
    #define LED_BUILTIN   PIN_PA3
  #else
    // standard Arduino pin 13
    #define LED_BUILTIN   PIN_PA3
  #endif
#endif

// standard Serial
#define SerialDebug       Serial

#define TIMER1_INTERVAL_MS        50UL

volatile uint32_t Timer1Count = 1;

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

void TimerHandler1()
{
  static bool toggle = false;

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

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

void setup()
{
  pinMode(LED_BUILTIN, OUTPUT);
  
  SerialDebug.begin(115200);
  while (!SerialDebug && millis() < 5000);

  SerialDebug.print(F("\nStarting Change_Interval on ")); SerialDebug.println(BOARD_NAME);
  SerialDebug.println(AT_TINY_TIMER_INTERRUPT_VERSION);
  SerialDebug.print(F("CPU Frequency = ")); SerialDebug.print(F_CPU / 1000000); SerialDebug.println(F(" MHz"));

  SerialDebug.print(F("TCB Clock Frequency = ")); 

#if USING_FULL_CLOCK  
  SerialDebug.println(F("Full clock (20/16MHz, etc) for highest accuracy"));
#elif USING_HALF_CLOCK  
  SerialDebug.println(F("Half clock (10/8MHz, etc.) for high accuracy"));
#else
  SerialDebug.println(F("250KHz for lower accuracy but longer time"));
#endif

  CurrentTimer.init();

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

#define CHECK_INTERVAL_MS     1000L
#define CHANGE_INTERVAL_MS    5000L

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) % 20;

      // 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)
      
      CurrentTimer.setInterval(TIMER1_INTERVAL_MS * (multFactor + 1), TimerHandler1);

      Timer1Count++;

      SerialDebug.print(F("Changing Interval, Timer = ")); SerialDebug.println(TIMER1_INTERVAL_MS * (multFactor + 1)); 
     
      lastChangeTime = currTime;
    }
  }
}