megaAVR_TimerInterrupt Library

Imagine you have a system with a mission-critical function, measuring water level and control the sump pump or doing something much more important. You normally use a software timer to poll, or even place the function in loop(). But what if another function is blocking the loop() or setup().

So your function might not be executed, and the result would be disastrous.

You'd prefer to have your function called, no matter what happening with other functions (busy loop, bug, etc.).

The correct choice is to use a Hardware Timer with Interrupt to call your function.

These hardware timers, using interrupt, still work even if other functions are blocking. Moreover, they are much more precise (certainly depending on clock frequency accuracy) than other software timers using millis() or micros(). That's necessary if you need to measure some data requiring better accuracy.

Functions using normal software timers, relying on loop() and calling millis(), won't work if the loop() or setup() is blocked by certain operation. For example, certain function is blocking while it's connecting to WiFi or some services.

The catch is your function is now part of an ISR (Interrupt Service Routine), and must be lean / mean, and follow certain rules. More to read on:

HOWTO Attach Interrupt

Important Notes about ISR

Inside the attached function, delay() won’t work and the value returned by millis() will not increment. Serial data received while in the function may be lost. You should declare as volatile any variables that you modify within the attached function.
Typically global variables are used to pass data between an ISR and the main program. To make sure variables shared between an ISR and the main program are updated correctly, declare them as volatile.

Currently supported Boards

Arduino UNO WiFi Rev2, AVR_NANO_EVERY, etc.
ATmega4809-based boards.

Prerequisites

Arduino IDE 1.8.19+ for Arduino.
Arduino megaAVR core 1.8.7+ for Arduino megaAVR boards. Use Arduino Board Manager to install.
MegaCoreX megaAVR core 1.1.0+ for Arduino megaAVR boards. . Follow How to install.
To use with certain example
- SimpleTimer library for ISR_Timers_Array_Simple and ISR_16_Timers_Array_Complex examples.

Installation

Use Arduino Library Manager

The best and easiest way is to use Arduino Library Manager. Search for megaAVR_TimerInterrupt, then select / install the latest version. You can also use this link for more detailed instructions.

Manual Install

Another way to install is to:

Navigate to megaAVR_TimerInterrupt page.
Download the latest release megaAVR_TimerInterrupt-main.zip.
Extract the zip file to megaAVR_TimerInterrupt-main directory
Copy whole megaAVR_TimerInterrupt-main folder to Arduino libraries' directory such as ~/Arduino/libraries/.

VS Code & PlatformIO:

Install VS Code
Install PlatformIO
Install megaAVR_TimerInterrupt library by using Library Manager. Search for megaAVR_TimerInterrupt in Platform.io Author's Libraries
Use included platformio.ini file from examples to ensure that all dependent libraries will installed automatically. Please visit documentation for the other options and examples at Project Configuration File

HOWTO Fix `Multiple Definitions` Linker Error

The current library implementation, using xyz-Impl.h instead of standard xyz.cpp, possibly creates certain Multiple Definitions Linker error in certain use cases.

You can include these .hpp files

// Can be included as many times as necessary, without `Multiple Definitions` Linker Error #include "megaAVR_TimerInterrupt.hpp" //https://github.com/khoih-prog/megaAVR_TimerInterrupt // Can be included as many times as necessary, without `Multiple Definitions` Linker Error #include "megaAVR_ISR_Timer.hpp" //https://github.com/khoih-prog/megaAVR_TimerInterrupt

in many files. But be sure to use the following .h files in just 1 .h, .cpp or .ino file, which must not be included in any other file, to avoid Multiple Definitions Linker Error

// To be included only in main(), .ino with setup() to avoid `Multiple Definitions` Linker Error #include "megaAVR_TimerInterrupt.h" //https://github.com/khoih-prog/megaAVR_TimerInterrupt // To be included only in main(), .ino with setup() to avoid `Multiple Definitions` Linker Error #include "megaAVR_ISR_Timer.h" //https://github.com/khoih-prog/megaAVR_TimerInterrupt

Check the new multiFileProject example for a HOWTO demo.

More useful Information

1. Documents

2. Timer TCB0-TCB3

TCB0-TCB3 are 16-bit timers.

Usage

Before using any Timer, you have to make sure the Timer has not been used by any other purpose.

1. Using only Hardware Timer directly

1.1 Init Hardware Timer

// Select USING_16MHZ == true for 16MHz to Timer TCBx => shorter timer, but better accuracy // Select USING_8MHZ == true for 8MHz to Timer TCBx => shorter timer, but better accuracy // Select USING_250KHZ == true for 250KHz to Timer TCBx => shorter timer, but better accuracy // Not select for default 250KHz to Timer TCBx => longer timer, but worse accuracy #define USING_16MHZ true #define USING_8MHZ false #define USING_250KHZ false // Select the timers you're using, here ITimer1 #define USE_TIMER_0 false #define USE_TIMER_1 true #define USE_TIMER_2 false #define USE_TIMER_3 false // Init timer ITimer1 ITimer1.init();

1.2 Set Hardware Timer Interval and attach Timer Interrupt Handler function

Use one of these functions with interval in unsigned long milliseconds

// interval (in ms) and duration (in milliseconds). Duration = 0 or not specified => run indefinitely template<typename TArg> bool setInterval(unsigned long interval, void (*callback)(TArg), TArg params, unsigned long duration = 0); // 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 = 0); // Interval (in ms) and duration (in milliseconds). Duration = 0 or not specified => run indefinitely template<typename TArg> bool attachInterruptInterval(unsigned long interval, void (*callback)(TArg), TArg params, unsigned long duration = 0); // Interval (in ms) and duration (in milliseconds). Duration = 0 or not specified => run indefinitely bool attachInterruptInterval(unsigned long interval, timer_callback callback, unsigned long duration = 0)

as follows

void TimerHandler1() { // Doing something here inside ISR } #define TIMER1_INTERVAL_MS 50L void setup() { .... // Interval in unsigned long millisecs if (ITimer1.attachInterruptInterval(TIMER1_INTERVAL_MS, TimerHandler1)) Serial.println("Starting ITimer1 OK, millis() = " + String(millis())); else Serial.println("Can't set ITimer1. Select another freq. or timer"); }

1.3 Set Hardware Timer Frequency and attach Timer Interrupt Handler function

Use one of these functions with frequency in float Hz

// frequency (in hertz) and duration (in milliseconds). Duration = 0 or not specified => run indefinitely bool setFrequency(float frequency, timer_callback_p callback, /* void* */ uint32_t params, unsigned long duration = 0); // frequency (in hertz) and duration (in milliseconds). Duration = 0 or not specified => run indefinitely bool setFrequency(float frequency, timer_callback callback, unsigned long duration = 0); // frequency (in hertz) and duration (in milliseconds). Duration = 0 or not specified => run indefinitely template<typename TArg> bool attachInterrupt(float frequency, void (*callback)(TArg), TArg params, unsigned long duration = 0); // frequency (in hertz) and duration (in milliseconds). Duration = 0 or not specified => run indefinitely bool attachInterrupt(float frequency, timer_callback callback, unsigned long duration = 0);

as follows

void TimerHandler1() { // Doing something here inside ISR } #define TIMER1_FREQ_HZ 5555.555 void setup() { .... // Frequency in float Hz if (ITimer1.attachInterrupt(TIMER1_FREQ_HZ, TimerHandler1)) Serial.println("Starting ITimer1 OK, millis() = " + String(millis())); else Serial.println("Can't set ITimer1. Select another freq. or timer"); }

2. Using 16 ISR_based Timers from 1 Hardware Timer

2.1 Important Note

The 16 ISR_based Timers, designed for long timer intervals, only support using unsigned long millisec intervals. If you have to use much higher frequency or sub-millisecond interval, you have to use the Hardware Timers directly as in 1.3 Set Hardware Timer Frequency and attach Timer Interrupt Handler function

2.2 Init Hardware Timer and ISR-based Timer

// Select USING_16MHZ == true for 16MHz to Timer TCBx => shorter timer, but better accuracy // Select USING_8MHZ == true for 8MHz to Timer TCBx => shorter timer, but better accuracy // Select USING_250KHZ == true for 250KHz to Timer TCBx => shorter timer, but better accuracy // Not select for default 250KHz to Timer TCBx => longer timer, but worse accuracy #define USING_16MHZ true #define USING_8MHZ false #define USING_250KHZ false #define USE_TIMER_0 false #define USE_TIMER_1 true #define USE_TIMER_2 false #define USE_TIMER_3 false // Init ISR_Timer // Each ISR_Timer can service 16 different ISR-based timers ISR_Timer ISR_Timer1;

2.3 Set Hardware Timer Interval and attach Timer Interrupt Handler functions

void TimerHandler() { ISR_Timer1.run(); } #define HW_TIMER_INTERVAL_MS 50L #define TIMER_INTERVAL_2S 2000L #define TIMER_INTERVAL_5S 5000L #define TIMER_INTERVAL_11S 11000L #define TIMER_INTERVAL_101S 101000L // In AVR, avoid doing something fancy in ISR, for example complex Serial.print with String() argument // The pure simple Serial.prints here are just for demonstration and testing. Must be eliminate in working environment // Or you can get this run-time error / crash void doingSomething2s() { // Doing something here inside ISR every 2 seconds } void doingSomething5s() { // Doing something here inside ISR every 5 seconds } void doingSomething11s() { // Doing something here inside ISR every 11 seconds } void doingSomething101s() { // Doing something here inside ISR every 101 seconds } void setup() { .... // Interval in millisecs if (ITimer.attachInterruptInterval(HW_TIMER_INTERVAL_MS, TimerHandler)) { lastMillis = millis(); Serial.println("Starting ITimer OK, millis() = " + String(lastMillis)); } else Serial.println("Can't set ITimer correctly. Select another freq. or interval"); // Just to demonstrate, don't use too many ISR Timers if not absolutely necessary // You can use up to 16 timer for each ISR_Timer ISR_Timer1.setInterval(TIMER_INTERVAL_2S, doingSomething2s); ISR_Timer1.setInterval(TIMER_INTERVAL_5S, doingSomething5s); ISR_Timer1.setInterval(TIMER_INTERVAL_11S, doingSomething11s); ISR_Timer1.setInterval(TIMER_INTERVAL_101S, doingSomething101s); }

Examples:

Example ISR_16_Timers_Array_Complex

megaAVR_TimerInterrupt/examples/ISR_16_Timers_Array_Complex/ISR_16_Timers_Array_Complex.ino

Lines 16 to 373 in 59d45e4

     #if !( defined(__AVR_ATmega4809__) || defined(ARDUINO_AVR_UNO_WIFI_REV2) || defined(ARDUINO_AVR_NANO_EVERY) || \  
   defined(ARDUINO_AVR_ATmega4809) || defined(ARDUINO_AVR_ATmega4808) || defined(ARDUINO_AVR_ATmega3209) || \  
   defined(ARDUINO_AVR_ATmega3208) || defined(ARDUINO_AVR_ATmega1609) || defined(ARDUINO_AVR_ATmega1608) || \  
   defined(ARDUINO_AVR_ATmega809) || defined(ARDUINO_AVR_ATmega808) )  
   #error This is designed only for Arduino or MegaCoreX 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_ 3  
    
   // Select USING_16MHZ == true for 16MHz to Timer TCBx => shorter timer, but better accuracy  
   // Select USING_8MHZ == true for 8MHz to Timer TCBx => shorter timer, but better accuracy  
   // Select USING_250KHZ == true for 250KHz to Timer TCBx => shorter timer, but better accuracy  
   // Not select for default 250KHz to Timer TCBx => longer timer, but worse accuracy  
   #define USING_16MHZ true  
   #define USING_8MHZ false  
   #define USING_250KHZ false  
    
    
   #define USE_TIMER_0 false  
   #define USE_TIMER_1 true  
   #define USE_TIMER_2 false  
   #define USE_TIMER_3 false  
    
   // To be included only in main(), .ino with setup() to avoid `Multiple Definitions` Linker Error  
   #include "megaAVR_TimerInterrupt.h"  
    
   // To be included only in main(), .ino with setup() to avoid `Multiple Definitions` Linker Error  
   #include "megaAVR_ISR_Timer.h"  
    
   #include <SimpleTimer.h> // https://github.com/jfturcot/SimpleTimer  
    
   #ifndef LED_BUILTIN  
  	#define LED_BUILTIN 13  
   #endif  
    
   ISR_Timer ISR_Timer1;  
    
   #define LED_TOGGLE_INTERVAL_MS 1000L  
    
   // You have to use longer time here if having problem because Arduino AVR clock is low, 16MHz => lower accuracy.  
   // Tested OK with 1ms when not much load => higher accuracy.  
   #define TIMER1_INTERVAL_MS 5L  
    
   volatile uint32_t startMillis = 0;  
    
   void TimerHandler1()  
   {  
   static bool toggle = false;  
   static int timeRun = 0;  
    
  	ISR_Timer1.run();  
    
   // Toggle LED every LED_TOGGLE_INTERVAL_MS = 2000ms = 2s  
   if (++timeRun == ((LED_TOGGLE_INTERVAL_MS) / TIMER1_INTERVAL_MS) )  
  	{  
  	timeRun = 0;  
    
   //timer interrupt toggles pin LED_BUILTIN  
   digitalWrite(LED_BUILTIN, toggle);  
  	toggle = !toggle;  
  	}  
   }  
    
   /////////////////////////////////////////////////  
    
   #define NUMBER_ISR_TIMERS 16  
    
   typedef void (*irqCallback) (void);  
    
   /////////////////////////////////////////////////  
    
   #define USE_COMPLEX_STRUCT true  
    
   #if USE_COMPLEX_STRUCT  
    
   typedef struct  
   {  
  	irqCallback irqCallbackFunc;  
   uint32_t TimerInterval;  
   unsigned long deltaMillis;  
   unsigned long previousMillis;  
   } ISRTimerData;  
    
   // In NRF52, avoid doing something fancy in ISR, for example Serial.print()  
   // The pure simple Serial.prints here are just for demonstration and testing. Must be eliminate in working environment  
   // Or you can get this run-time error / crash  
    
   void doingSomething(int index);  
    
   #else  
    
   volatile unsigned long deltaMillis [NUMBER_ISR_TIMERS] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };  
   volatile unsigned long previousMillis [NUMBER_ISR_TIMERS] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };  
    
   // You can assign any interval for any timer here, in milliseconds  
   uint32_t TimerInterval[NUMBER_ISR_TIMERS] =  
   {  
   5000L, 10000L, 15000L, 20000L, 25000L, 30000L, 35000L, 40000L,  
   45000L, 50000L, 55000L, 60000L, 65000L, 70000L, 75000L, 80000L  
   };  
    
   void doingSomething(int index)  
   {  
   unsigned long currentMillis = millis();  
    
  	deltaMillis[index] = currentMillis - previousMillis[index];  
  	previousMillis[index] = currentMillis;  
   }  
    
   #endif  
    
   ////////////////////////////////////  
   // Shared  
   ////////////////////////////////////  
    
   void doingSomething0()  
   {  
   doingSomething(0);  
   }  
    
   void doingSomething1()  
   {  
   doingSomething(1);  
   }  
    
   void doingSomething2()  
   {  
   doingSomething(2);  
   }  
    
   void doingSomething3()  
   {  
   doingSomething(3);  
   }  
    
   void doingSomething4()  
   {  
   doingSomething(4);  
   }  
    
   void doingSomething5()  
   {  
   doingSomething(5);  
   }  
    
   void doingSomething6()  
   {  
   doingSomething(6);  
   }  
    
   void doingSomething7()  
   {  
   doingSomething(7);  
   }  
    
   void doingSomething8()  
   {  
   doingSomething(8);  
   }  
    
   void doingSomething9()  
   {  
   doingSomething(9);  
   }  
    
   void doingSomething10()  
   {  
   doingSomething(10);  
   }  
    
   void doingSomething11()  
   {  
   doingSomething(11);  
   }  
    
   void doingSomething12()  
   {  
   doingSomething(12);  
   }  
    
   void doingSomething13()  
   {  
   doingSomething(13);  
   }  
    
   void doingSomething14()  
   {  
   doingSomething(14);  
   }  
    
   void doingSomething15()  
   {  
   doingSomething(15);  
   }  
    
   #if USE_COMPLEX_STRUCT  
    
   ISRTimerData curISRTimerData[NUMBER_ISR_TIMERS] =  
   {  
   //irqCallbackFunc, TimerInterval, deltaMillis, previousMillis  
  	{ doingSomething0, 5000L, 0, 0 },  
  	{ doingSomething1, 10000L, 0, 0 },  
  	{ doingSomething2, 15000L, 0, 0 },  
  	{ doingSomething3, 20000L, 0, 0 },  
  	{ doingSomething4, 25000L, 0, 0 },  
  	{ doingSomething5, 30000L, 0, 0 },  
  	{ doingSomething6, 35000L, 0, 0 },  
  	{ doingSomething7, 40000L, 0, 0 },  
  	{ doingSomething8, 45000L, 0, 0 },  
  	{ doingSomething9, 50000L, 0, 0 },  
  	{ doingSomething10, 55000L, 0, 0 },  
  	{ doingSomething11, 60000L, 0, 0 },  
  	{ doingSomething12, 65000L, 0, 0 },  
  	{ doingSomething13, 70000L, 0, 0 },  
  	{ doingSomething14, 75000L, 0, 0 },  
  	{ doingSomething15, 80000L, 0, 0 }  
   };  
    
   void doingSomething(int index)  
   {  
   unsigned long currentMillis = millis();  
    
  	curISRTimerData[index].deltaMillis = currentMillis - curISRTimerData[index].previousMillis;  
  	curISRTimerData[index].previousMillis = currentMillis;  
   }  
    
   #else  
    
   irqCallback irqCallbackFunc[NUMBER_ISR_TIMERS] =  
   {  
  	doingSomething0, doingSomething1, doingSomething2, doingSomething3,  
  	doingSomething4, doingSomething5, doingSomething6, doingSomething7,  
  	doingSomething8, doingSomething9, doingSomething10, doingSomething11,  
  	doingSomething12, doingSomething13, doingSomething14, doingSomething15  
   };  
    
   #endif  
    
   ////////////////////////////////////////////////  
    
    
   #define SIMPLE_TIMER_MS 2000L  
    
   // Init SimpleTimer  
   SimpleTimer simpleTimer;  
    
   // Here is software Timer, you can do somewhat fancy stuffs without many issues.  
   // But always avoid  
   // 1. Long delay() it just doing nothing and pain-without-gain wasting CPU power.Plan and design your code / strategy ahead  
   // 2. Very long "do", "while", "for" loops without predetermined exit time.  
   void simpleTimerDoingSomething2s()  
   {  
   static unsigned long previousMillis = startMillis;  
    
   unsigned long currMillis = millis();  
    
  	Serial.print(F("SimpleTimer : "));  
  	Serial.print(SIMPLE_TIMER_MS / 1000);  
  	Serial.print(F(", ms : "));  
  	Serial.print(currMillis);  
  	Serial.print(F(", Dms : "));  
  	Serial.println(currMillis - previousMillis);  
    
   for (uint16_t i = 0; i < NUMBER_ISR_TIMERS; i++)  
  	{  
   #if USE_COMPLEX_STRUCT  
  	Serial.print(F("Timer : "));  
  	Serial.print(i);  
  	Serial.print(F(", programmed : "));  
  	Serial.print(curISRTimerData[i].TimerInterval);  
  	Serial.print(F(", actual : "));  
  	Serial.println(curISRTimerData[i].deltaMillis);  
   #else  
  	Serial.print(F("Timer : "));  
  	Serial.print(i);  
  	Serial.print(F(", programmed : "));  
  	Serial.print(TimerInterval[i]);  
  	Serial.print(F(", actual : "));  
  	Serial.println(deltaMillis[i]);  
   #endif  
  	}  
    
  	previousMillis = currMillis;  
   }  
    
   void setup()  
   {  
   pinMode(LED_BUILTIN, OUTPUT);  
    
  	Serial.begin(115200);  
    
   while (!Serial);  
    
  	Serial.print(F("\nStarting ISR_16_Timers_Array_Complex on "));  
  	Serial.println(BOARD_NAME);  
  	Serial.println(MEGA_AVR_TIMER_INTERRUPT_VERSION);  
  	Serial.print(F("CPU Frequency = "));  
  	Serial.print(F_CPU / 1000000);  
  	Serial.println(F(" MHz"));  
    
  	Serial.print(F("TCB Clock Frequency = "));  
    
   #if USING_16MHZ  
  	Serial.println(F("16MHz for highest accuracy"));  
   #elif USING_8MHZ  
  	Serial.println(F("8MHz for very high accuracy"));  
   #else  
  	Serial.println(F("250KHz for lower accuracy but longer time"));  
   #endif  
    
  	ITimer1.init();  
    
   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"));  
    
   //ISR_Timer1.setInterval(2000L, doingSomething2s);  
   //ISR_Timer1.setInterval(5000L, doingSomething5s);  
    
   // Just to demonstrate, don't use too many ISR Timers if not absolutely necessary  
   // You can use up to 16 timer for each ISR_Timer  
   for (uint16_t i = 0; i < NUMBER_ISR_TIMERS; i++)  
  	{  
   #if USE_COMPLEX_STRUCT  
  	curISRTimerData[i].previousMillis = startMillis;  
  	ISR_Timer1.setInterval(curISRTimerData[i].TimerInterval, curISRTimerData[i].irqCallbackFunc);  
   #else  
  	previousMillis[i] = startMillis;  
  	ISR_Timer1.setInterval(TimerInterval[i], irqCallbackFunc[i]);  
   #endif  
  	}  
    
   // You need this timer for non-critical tasks. Avoid abusing ISR if not absolutely necessary.  
  	simpleTimer.setInterval(SIMPLE_TIMER_MS, simpleTimerDoingSomething2s);  
   }  
    
   #define BLOCKING_TIME_MS 10000L  
    
   void loop()  
   {  
   // This unadvised blocking task is used to demonstrate the blocking effects onto the execution and accuracy to Software timer  
   // You see the time elapse of ISR_Timer still accurate, whereas very unaccurate for Software Timer  
   // The time elapse for 2000ms software timer now becomes 3000ms (BLOCKING_TIME_MS)  
   // While that of ISR_Timer is still prefect.  
   delay(BLOCKING_TIME_MS);  
    
   // You need this Software timer for non-critical tasks. Avoid abusing ISR if not absolutely necessary  
   // You don't need to and never call ISR_Timer.run() here in the loop(). It's already handled by ISR timer.  
  	simpleTimer.run();  
   }  
 

Debug Terminal Output Samples

1. ISR_16_Timers_Array_Complex on Arduino megaAVR Nano Every

The following is the sample terminal output when running example ISR_16_Timers_Array_Complex on Arduino megaAVR Nano Every to demonstrate the accuracy of ISR Hardware Timer, especially when system is very busy. The ISR timer is programmed for 2s, is activated exactly after 2.000s !!!

While software timer, **programmed for 2s, is activated after more than 10.000s in loop().

Starting ISR_16_Timers_Array_Complex on megaAVR Nano Every megaAVR_TimerInterrupt v1.7.0 CPU Frequency = 16 MHz TCB Clock Frequency = 250KHz for lower accuracy but longer time Starting ITimer1 OK, millis() = 6 SimpleTimer : 2, ms : 10006, Dms : 10006 Timer : 0, programmed : 5000, actual : 5006 Timer : 1, programmed : 10000, actual : 10010 Timer : 2, programmed : 15000, actual : 0 Timer : 3, programmed : 20000, actual : 0 Timer : 4, programmed : 25000, actual : 0 Timer : 5, programmed : 30000, actual : 0 Timer : 6, programmed : 35000, actual : 0 Timer : 7, programmed : 40000, actual : 0 Timer : 8, programmed : 45000, actual : 0 Timer : 9, programmed : 50000, actual : 0 Timer : 10, programmed : 55000, actual : 0 Timer : 11, programmed : 60000, actual : 0 Timer : 12, programmed : 65000, actual : 0 Timer : 13, programmed : 70000, actual : 0 Timer : 14, programmed : 75000, actual : 0 Timer : 15, programmed : 80000, actual : 0 SimpleTimer : 2, ms : 20065, Dms : 10059 Timer : 0, programmed : 5000, actual : 4994 Timer : 1, programmed : 10000, actual : 9998 Timer : 2, programmed : 15000, actual : 15014 Timer : 3, programmed : 20000, actual : 20008 Timer : 4, programmed : 25000, actual : 0 Timer : 5, programmed : 30000, actual : 0 Timer : 6, programmed : 35000, actual : 0 Timer : 7, programmed : 40000, actual : 0 Timer : 8, programmed : 45000, actual : 0 Timer : 9, programmed : 50000, actual : 0 Timer : 10, programmed : 55000, actual : 0 Timer : 11, programmed : 60000, actual : 0 Timer : 12, programmed : 65000, actual : 0 Timer : 13, programmed : 70000, actual : 0 Timer : 14, programmed : 75000, actual : 0 Timer : 15, programmed : 80000, actual : 0 SimpleTimer : 2, ms : 30125, Dms : 10060 Timer : 0, programmed : 5000, actual : 4994 Timer : 1, programmed : 10000, actual : 9998 Timer : 2, programmed : 15000, actual : 14992 Timer : 3, programmed : 20000, actual : 20008 Timer : 4, programmed : 25000, actual : 25012 Timer : 5, programmed : 30000, actual : 30006 Timer : 6, programmed : 35000, actual : 0 Timer : 7, programmed : 40000, actual : 0 Timer : 8, programmed : 45000, actual : 0 Timer : 9, programmed : 50000, actual : 0 Timer : 10, programmed : 55000, actual : 0 Timer : 11, programmed : 60000, actual : 0 Timer : 12, programmed : 65000, actual : 0 Timer : 13, programmed : 70000, actual : 0 Timer : 14, programmed : 75000, actual : 0 Timer : 15, programmed : 80000, actual : 0 SimpleTimer : 2, ms : 40184, Dms : 10059 Timer : 0, programmed : 5000, actual : 5004 Timer : 1, programmed : 10000, actual : 10008 Timer : 2, programmed : 15000, actual : 14992 Timer : 3, programmed : 20000, actual : 20006 Timer : 4, programmed : 25000, actual : 25012 Timer : 5, programmed : 30000, actual : 30006 Timer : 6, programmed : 35000, actual : 35010 Timer : 7, programmed : 40000, actual : 40014 Timer : 8, programmed : 45000, actual : 0 Timer : 9, programmed : 50000, actual : 0 Timer : 10, programmed : 55000, actual : 0 Timer : 11, programmed : 60000, actual : 0 Timer : 12, programmed : 65000, actual : 0 Timer : 13, programmed : 70000, actual : 0 Timer : 14, programmed : 75000, actual : 0 Timer : 15, programmed : 80000, actual : 0 SimpleTimer : 2, ms : 50245, Dms : 10061 Timer : 0, programmed : 5000, actual : 5004 Timer : 1, programmed : 10000, actual : 9998 Timer : 2, programmed : 15000, actual : 15002 Timer : 3, programmed : 20000, actual : 20006 Timer : 4, programmed : 25000, actual : 25000 Timer : 5, programmed : 30000, actual : 30006 Timer : 6, programmed : 35000, actual : 35010 Timer : 7, programmed : 40000, actual : 40014 Timer : 8, programmed : 45000, actual : 45008 Timer : 9, programmed : 50000, actual : 50012 Timer : 10, programmed : 55000, actual : 0 Timer : 11, programmed : 60000, actual : 0 Timer : 12, programmed : 65000, actual : 0 Timer : 13, programmed : 70000, actual : 0 Timer : 14, programmed : 75000, actual : 0 Timer : 15, programmed : 80000, actual : 0 SimpleTimer : 2, ms : 60307, Dms : 10062 Timer : 0, programmed : 5000, actual : 5004 Timer : 1, programmed : 10000, actual : 9998 Timer : 2, programmed : 15000, actual : 15002 Timer : 3, programmed : 20000, actual : 19996 Timer : 4, programmed : 25000, actual : 25000 Timer : 5, programmed : 30000, actual : 30004 Timer : 6, programmed : 35000, actual : 35010 Timer : 7, programmed : 40000, actual : 40014 Timer : 8, programmed : 45000, actual : 45008 Timer : 9, programmed : 50000, actual : 50012 Timer : 10, programmed : 55000, actual : 55006 Timer : 11, programmed : 60000, actual : 60010 Timer : 12, programmed : 65000, actual : 0 Timer : 13, programmed : 70000, actual : 0 Timer : 14, programmed : 75000, actual : 0 Timer : 15, programmed : 80000, actual : 0 SimpleTimer : 2, ms : 70369, Dms : 10062 Timer : 0, programmed : 5000, actual : 4994 Timer : 1, programmed : 10000, actual : 9998 Timer : 2, programmed : 15000, actual : 15002 Timer : 3, programmed : 20000, actual : 19996 Timer : 4, programmed : 25000, actual : 25000 Timer : 5, programmed : 30000, actual : 30004 Timer : 6, programmed : 35000, actual : 34998 Timer : 7, programmed : 40000, actual : 40014 Timer : 8, programmed : 45000, actual : 45008 Timer : 9, programmed : 50000, actual : 50012 Timer : 10, programmed : 55000, actual : 55006 Timer : 11, programmed : 60000, actual : 60010 Timer : 12, programmed : 65000, actual : 65014 Timer : 13, programmed : 70000, actual : 70008 Timer : 14, programmed : 75000, actual : 0 Timer : 15, programmed : 80000, actual : 0 SimpleTimer : 2, ms : 80432, Dms : 10063 Timer : 0, programmed : 5000, actual : 4994 Timer : 1, programmed : 10000, actual : 9998 Timer : 2, programmed : 15000, actual : 15002 Timer : 3, programmed : 20000, actual : 19996 Timer : 4, programmed : 25000, actual : 25000 Timer : 5, programmed : 30000, actual : 30004 Timer : 6, programmed : 35000, actual : 34998 Timer : 7, programmed : 40000, actual : 39992 Timer : 8, programmed : 45000, actual : 45008 Timer : 9, programmed : 50000, actual : 50012 Timer : 10, programmed : 55000, actual : 55006 Timer : 11, programmed : 60000, actual : 60010 Timer : 12, programmed : 65000, actual : 65014 Timer : 13, programmed : 70000, actual : 70008 Timer : 14, programmed : 75000, actual : 75012 Timer : 15, programmed : 80000, actual : 80016

2. Change_Interval on Arduino megaAVR Nano Every

The following is the sample terminal output when running example Change_Interval on Arduino megaAVR Nano Every to demonstrate how to change Timer Interval on-the-fly

Starting Change_Interval on megaAVR Nano Every megaAVR_TimerInterrupt v1.7.0 CPU Frequency = 16 MHz TCB Clock Frequency = 250KHz for lower accuracy but longer time Starting ITimer1 OK, millis() = 1 Starting ITimer2 OK, millis() = 4 Time = 10001, Timer1Count = 97, Timer2Count = 49 Time = 20002, Timer1Count = 195, Timer2Count = 99 Changing Interval, Timer1 = 200, Timer2 = 400 Time = 30003, Timer1Count = 244, Timer2Count = 123 Time = 40004, Timer1Count = 294, Timer2Count = 148 Changing Interval, Timer1 = 100, Timer2 = 200 Time = 50006, Timer1Count = 391, Timer2Count = 197 Time = 60007, Timer1Count = 489, Timer2Count = 247 Changing Interval, Timer1 = 200, Timer2 = 400 Time = 70008, Timer1Count = 538, Timer2Count = 271 Time = 80009, Timer1Count = 588, Timer2Count = 296 Changing Interval, Timer1 = 100, Timer2 = 200

3. ISR_16_Timers_Array_Complex on Arduino megaAVR Nano Every to show accuracy difference.

3.1. TCB Clock Frequency 16MHz for highest accuracy

Starting ISR_16_Timers_Array_Complex on megaAVR Nano Every megaAVR_TimerInterrupt v1.7.0 CPU Frequency = 16 MHz TCB Clock Frequency = 16MHz for highest accuracy Starting ITimer1 OK, millis() = 6 SimpleTimer : 2, ms : 10007, Dms : 10007 Timer : 0, programmed : 5000, actual : 5000 Timer : 1, programmed : 10000, actual : 10006 Timer : 2, programmed : 15000, actual : 0 Timer : 3, programmed : 20000, actual : 0 Timer : 4, programmed : 25000, actual : 0 Timer : 5, programmed : 30000, actual : 0 Timer : 6, programmed : 35000, actual : 0 Timer : 7, programmed : 40000, actual : 0 Timer : 8, programmed : 45000, actual : 0 Timer : 9, programmed : 50000, actual : 0 Timer : 10, programmed : 55000, actual : 0 Timer : 11, programmed : 60000, actual : 0 Timer : 12, programmed : 65000, actual : 0 Timer : 13, programmed : 70000, actual : 0 Timer : 14, programmed : 75000, actual : 0 Timer : 15, programmed : 80000, actual : 0 SimpleTimer : 2, ms : 20066, Dms : 10059 Timer : 0, programmed : 5000, actual : 5000 Timer : 1, programmed : 10000, actual : 10000 Timer : 2, programmed : 15000, actual : 15006 Timer : 3, programmed : 20000, actual : 20006 Timer : 4, programmed : 25000, actual : 0 Timer : 5, programmed : 30000, actual : 0 Timer : 6, programmed : 35000, actual : 0 Timer : 7, programmed : 40000, actual : 0 Timer : 8, programmed : 45000, actual : 0 Timer : 9, programmed : 50000, actual : 0 Timer : 10, programmed : 55000, actual : 0 Timer : 11, programmed : 60000, actual : 0 Timer : 12, programmed : 65000, actual : 0 Timer : 13, programmed : 70000, actual : 0 Timer : 14, programmed : 75000, actual : 0 Timer : 15, programmed : 80000, actual : 0 ... SimpleTimer : 2, ms : 211269, Dms : 10064 Timer : 0, programmed : 5000, actual : 5000 <========== Very accurate @ clock 16MHz Timer : 1, programmed : 10000, actual : 10000 Timer : 2, programmed : 15000, actual : 15000 Timer : 3, programmed : 20000, actual : 20000 Timer : 4, programmed : 25000, actual : 25000 Timer : 5, programmed : 30000, actual : 30000 Timer : 6, programmed : 35000, actual : 35000 Timer : 7, programmed : 40000, actual : 40000 Timer : 8, programmed : 45000, actual : 45000 Timer : 9, programmed : 50000, actual : 50000 Timer : 10, programmed : 55000, actual : 55000 Timer : 11, programmed : 60000, actual : 60000 Timer : 12, programmed : 65000, actual : 65000 Timer : 13, programmed : 70000, actual : 70000 Timer : 14, programmed : 75000, actual : 75000 Timer : 15, programmed : 80000, actual : 80000 SimpleTimer : 2, ms : 221333, Dms : 10064 Timer : 0, programmed : 5000, actual : 5000 Timer : 1, programmed : 10000, actual : 10000 Timer : 2, programmed : 15000, actual : 15000 Timer : 3, programmed : 20000, actual : 20000 Timer : 4, programmed : 25000, actual : 25000 Timer : 5, programmed : 30000, actual : 30000 Timer : 6, programmed : 35000, actual : 35000 Timer : 7, programmed : 40000, actual : 40000 Timer : 8, programmed : 45000, actual : 45000 Timer : 9, programmed : 50000, actual : 50000 Timer : 10, programmed : 55000, actual : 55000 Timer : 11, programmed : 60000, actual : 60000 Timer : 12, programmed : 65000, actual : 65000 Timer : 13, programmed : 70000, actual : 70000 Timer : 14, programmed : 75000, actual : 75000 Timer : 15, programmed : 80000, actual : 80000

3.2. TCB Clock Frequency 8MHz for very high accuracy

 Starting ISR_16_Timers_Array_Complex on megaAVR Nano Every megaAVR_TimerInterrupt v1.7.0 CPU Frequency = 16 MHz TCB Clock Frequency = 8MHz for very high accuracy Starting ITimer1 OK, millis() = 10 SimpleTimer : 2, ms : 10011, Dms : 10011 Timer : 0, programmed : 5000, actual : 5000 Timer : 1, programmed : 10000, actual : 10011 Timer : 2, programmed : 15000, actual : 0 Timer : 3, programmed : 20000, actual : 0 Timer : 4, programmed : 25000, actual : 0 Timer : 5, programmed : 30000, actual : 0 Timer : 6, programmed : 35000, actual : 0 Timer : 7, programmed : 40000, actual : 0 Timer : 8, programmed : 45000, actual : 0 Timer : 9, programmed : 50000, actual : 0 Timer : 10, programmed : 55000, actual : 0 Timer : 11, programmed : 60000, actual : 0 Timer : 12, programmed : 65000, actual : 0 Timer : 13, programmed : 70000, actual : 0 Timer : 14, programmed : 75000, actual : 0 Timer : 15, programmed : 80000, actual : 0 ... SimpleTimer : 2, ms : 160949, Dms : 10064 Timer : 0, programmed : 5000, actual : 5000 <========== Very accurate @ clock 8MHz Timer : 1, programmed : 10000, actual : 10000 Timer : 2, programmed : 15000, actual : 15000 Timer : 3, programmed : 20000, actual : 20000 Timer : 4, programmed : 25000, actual : 25000 Timer : 5, programmed : 30000, actual : 30000 Timer : 6, programmed : 35000, actual : 35000 Timer : 7, programmed : 40000, actual : 40000 Timer : 8, programmed : 45000, actual : 45000 Timer : 9, programmed : 50000, actual : 50000 Timer : 10, programmed : 55000, actual : 55000 Timer : 11, programmed : 60000, actual : 60000 Timer : 12, programmed : 65000, actual : 65000 Timer : 13, programmed : 70000, actual : 70000 Timer : 14, programmed : 75000, actual : 75000 Timer : 15, programmed : 80000, actual : 80000 SimpleTimer : 2, ms : 171013, Dms : 10064 Timer : 0, programmed : 5000, actual : 5000 Timer : 1, programmed : 10000, actual : 10000 Timer : 2, programmed : 15000, actual : 15000 Timer : 3, programmed : 20000, actual : 20000 Timer : 4, programmed : 25000, actual : 25000 Timer : 5, programmed : 30000, actual : 30000 Timer : 6, programmed : 35000, actual : 35000 Timer : 7, programmed : 40000, actual : 40000 Timer : 8, programmed : 45000, actual : 45000 Timer : 9, programmed : 50000, actual : 50000 Timer : 10, programmed : 55000, actual : 55000 Timer : 11, programmed : 60000, actual : 60000 Timer : 12, programmed : 65000, actual : 65000 Timer : 13, programmed : 70000, actual : 70000 Timer : 14, programmed : 75000, actual : 75000 Timer : 15, programmed : 80000, actual : 80000

3.3. TCB Clock Frequency 250KHz for lower accuracy but longer time

Starting ISR_16_Timers_Array_Complex on megaAVR Nano Every megaAVR_TimerInterrupt v1.7.0 CPU Frequency = 16 MHz TCB Clock Frequency = 250KHz for lower accuracy but longer time Starting ITimer1 OK, millis() = 11 SimpleTimer : 2, ms : 10012, Dms : 10012 Timer : 0, programmed : 5000, actual : 5021 Timer : 1, programmed : 10000, actual : 10015 Timer : 2, programmed : 15000, actual : 0 Timer : 3, programmed : 20000, actual : 0 Timer : 4, programmed : 25000, actual : 0 Timer : 5, programmed : 30000, actual : 0 Timer : 6, programmed : 35000, actual : 0 Timer : 7, programmed : 40000, actual : 0 Timer : 8, programmed : 45000, actual : 0 Timer : 9, programmed : 50000, actual : 0 Timer : 10, programmed : 55000, actual : 0 Timer : 11, programmed : 60000, actual : 0 Timer : 12, programmed : 65000, actual : 0 Timer : 13, programmed : 70000, actual : 0 Timer : 14, programmed : 75000, actual : 0 Timer : 15, programmed : 80000, actual : 0 SimpleTimer : 2, ms : 20071, Dms : 10059 Timer : 0, programmed : 5000, actual : 4994 Timer : 1, programmed : 10000, actual : 9999 Timer : 2, programmed : 15000, actual : 15020 Timer : 3, programmed : 20000, actual : 20014 Timer : 4, programmed : 25000, actual : 0 Timer : 5, programmed : 30000, actual : 0 Timer : 6, programmed : 35000, actual : 0 Timer : 7, programmed : 40000, actual : 0 Timer : 8, programmed : 45000, actual : 0 Timer : 9, programmed : 50000, actual : 0 Timer : 10, programmed : 55000, actual : 0 Timer : 11, programmed : 60000, actual : 0 Timer : 12, programmed : 65000, actual : 0 Timer : 13, programmed : 70000, actual : 0 Timer : 14, programmed : 75000, actual : 0 Timer : 15, programmed : 80000, actual : 0 ... SimpleTimer : 2, ms : 845278, Dms : 10063 Timer : 0, programmed : 5000, actual : 4994 <========== Less accurate @ clock 250KHz Timer : 1, programmed : 10000, actual : 9997 Timer : 2, programmed : 15000, actual : 15001 Timer : 3, programmed : 20000, actual : 20005 Timer : 4, programmed : 25000, actual : 25000 Timer : 5, programmed : 30000, actual : 30004 Timer : 6, programmed : 35000, actual : 34998 Timer : 7, programmed : 40000, actual : 40001 Timer : 8, programmed : 45000, actual : 44995 Timer : 9, programmed : 50000, actual : 50000 Timer : 10, programmed : 55000, actual : 55004 Timer : 11, programmed : 60000, actual : 59998 Timer : 12, programmed : 65000, actual : 64992 Timer : 13, programmed : 70000, actual : 70005 Timer : 14, programmed : 75000, actual : 75000 Timer : 15, programmed : 80000, actual : 80004 SimpleTimer : 2, ms : 855342, Dms : 10064 Timer : 0, programmed : 5000, actual : 5004 Timer : 1, programmed : 10000, actual : 9999 Timer : 2, programmed : 15000, actual : 15003 Timer : 3, programmed : 20000, actual : 20005 Timer : 4, programmed : 25000, actual : 25000 Timer : 5, programmed : 30000, actual : 30004 Timer : 6, programmed : 35000, actual : 34998 Timer : 7, programmed : 40000, actual : 40001 Timer : 8, programmed : 45000, actual : 45007 Timer : 9, programmed : 50000, actual : 50000 Timer : 10, programmed : 55000, actual : 55004 Timer : 11, programmed : 60000, actual : 59998 Timer : 12, programmed : 65000, actual : 64992 Timer : 13, programmed : 70000, actual : 70005 Timer : 14, programmed : 75000, actual : 75000 Timer : 15, programmed : 80000, actual : 80004

4. Change_Interval_HF on Arduino megaAVR Nano Every

The following is the sample terminal output when running example Change_Interval_HF on Arduino megaAVR Nano Every to demonstrate how to change High Frequency Timer Interval on-the-fly

Starting Change_Interval_HF on megaAVR Nano Every megaAVR_TimerInterrupt v1.7.0 CPU Frequency = 16 MHz TCB Clock Frequency = 16MHz for highest accuracy [TISR] TCB 1 [TISR] ================== [TISR] Init, Timer = 1 [TISR] CTRLB = 0 [TISR] CCMP = 65535 [TISR] INTCTRL = 0 [TISR] CTRLA = 1 [TISR] ================== [TISR] Frequency = 10000.00 , CLK_TCB_FREQ = 16000000 [TISR] setFrequency: _CCMPValueRemaining = 1600 Starting ITimer1 OK, millis() = 12 Frequency, Timer1 = 10000 Time = 10001, Timer1Count = 99856 Time = 20002, Timer1Count = 199807 [TISR] Frequency = 5000.00 , CLK_TCB_FREQ = 16000000 [TISR] setFrequency: _CCMPValueRemaining = 3200 Changing Frequency, Timer1 = 5000 Time = 30003, Timer1Count = 249792 Time = 40004, Timer1Count = 299784 [TISR] Frequency = 10000.00 , CLK_TCB_FREQ = 16000000 [TISR] setFrequency: _CCMPValueRemaining = 1600 Changing Frequency, Timer1 = 10000

5. ISR_16_Timers_Array_Complex on Arduino megaAVR Nano Every using MegaCoreX

The following is the sample terminal output when running example ISR_16_Timers_Array_Complex on Arduino megaAVR Nano Every using MegaCoreX to demonstrate the accuracy of ISR Hardware Timer, especially when system is very busy. The ISR timer is programmed for 2s, is activated exactly after 2.000s !!!

While software timer, **programmed for 2s, is activated after more than 10.000s in loop().

Starting ISR_16_Timers_Array_Complex on MegaCoreX ATmega4809 megaAVR_TimerInterrupt v1.7.0 CPU Frequency = 16 MHz TCB Clock Frequency = 16MHz for highest accuracy [TISR] TCB1 [TISR] ================== [TISR] Init, Timer = 1 [TISR] CTRLB = 0 [TISR] CCMP = 65535 [TISR] INTCTRL = 0 [TISR] CTRLA = 1 [TISR] ================== [TISR] Frequency = 200.00, CLK_TCB_FREQ = 16000000 [TISR] setFrequency: _CCMPValueRemaining = 80000 Starting ITimer1 OK, millis() = 12 SimpleTimer : 2, ms : 10013, Dms : 10013 Timer : 0, programmed : 5000, actual : 5016 Timer : 1, programmed : 10000, actual : 10016 Timer : 2, programmed : 15000, actual : 0 Timer : 3, programmed : 20000, actual : 0 Timer : 4, programmed : 25000, actual : 0 Timer : 5, programmed : 30000, actual : 0 Timer : 6, programmed : 35000, actual : 0 Timer : 7, programmed : 40000, actual : 0 Timer : 8, programmed : 45000, actual : 0 Timer : 9, programmed : 50000, actual : 0 Timer : 10, programmed : 55000, actual : 0 Timer : 11, programmed : 60000, actual : 0 Timer : 12, programmed : 65000, actual : 0 Timer : 13, programmed : 70000, actual : 0 Timer : 14, programmed : 75000, actual : 0 Timer : 15, programmed : 80000, actual : 0 SimpleTimer : 2, ms : 20072, Dms : 10059 Timer : 0, programmed : 5000, actual : 5000 Timer : 1, programmed : 10000, actual : 10000 Timer : 2, programmed : 15000, actual : 15016 Timer : 3, programmed : 20000, actual : 20016 Timer : 4, programmed : 25000, actual : 0 Timer : 5, programmed : 30000, actual : 0 Timer : 6, programmed : 35000, actual : 0 Timer : 7, programmed : 40000, actual : 0 Timer : 8, programmed : 45000, actual : 0 Timer : 9, programmed : 50000, actual : 0 Timer : 10, programmed : 55000, actual : 0 Timer : 11, programmed : 60000, actual : 0 Timer : 12, programmed : 65000, actual : 0 Timer : 13, programmed : 70000, actual : 0 Timer : 14, programmed : 75000, actual : 0 Timer : 15, programmed : 80000, actual : 0 SimpleTimer : 2, ms : 30132, Dms : 10060 Timer : 0, programmed : 5000, actual : 5000 Timer : 1, programmed : 10000, actual : 10001 Timer : 2, programmed : 15000, actual : 15001 Timer : 3, programmed : 20000, actual : 20016 Timer : 4, programmed : 25000, actual : 25017 Timer : 5, programmed : 30000, actual : 30017 Timer : 6, programmed : 35000, actual : 0 Timer : 7, programmed : 40000, actual : 0 Timer : 8, programmed : 45000, actual : 0 Timer : 9, programmed : 50000, actual : 0 Timer : 10, programmed : 55000, actual : 0 Timer : 11, programmed : 60000, actual : 0 Timer : 12, programmed : 65000, actual : 0 Timer : 13, programmed : 70000, actual : 0 Timer : 14, programmed : 75000, actual : 0 Timer : 15, programmed : 80000, actual : 0 SimpleTimer : 2, ms : 40192, Dms : 10060 Timer : 0, programmed : 5000, actual : 5000 Timer : 1, programmed : 10000, actual : 10000 Timer : 2, programmed : 15000, actual : 15001 Timer : 3, programmed : 20000, actual : 20001 Timer : 4, programmed : 25000, actual : 25017 Timer : 5, programmed : 30000, actual : 30017 Timer : 6, programmed : 35000, actual : 35017 Timer : 7, programmed : 40000, actual : 40017 Timer : 8, programmed : 45000, actual : 0 Timer : 9, programmed : 50000, actual : 0 Timer : 10, programmed : 55000, actual : 0 Timer : 11, programmed : 60000, actual : 0 Timer : 12, programmed : 65000, actual : 0 Timer : 13, programmed : 70000, actual : 0 Timer : 14, programmed : 75000, actual : 0 Timer : 15, programmed : 80000, actual : 0 SimpleTimer : 2, ms : 50253, Dms : 10061 Timer : 0, programmed : 5000, actual : 5000 Timer : 1, programmed : 10000, actual : 10000 Timer : 2, programmed : 15000, actual : 15000 Timer : 3, programmed : 20000, actual : 20001 Timer : 4, programmed : 25000, actual : 25000 Timer : 5, programmed : 30000, actual : 30017 Timer : 6, programmed : 35000, actual : 35017 Timer : 7, programmed : 40000, actual : 40017 Timer : 8, programmed : 45000, actual : 45017 Timer : 9, programmed : 50000, actual : 50017 Timer : 10, programmed : 55000, actual : 0 Timer : 11, programmed : 60000, actual : 0 Timer : 12, programmed : 65000, actual : 0 Timer : 13, programmed : 70000, actual : 0 Timer : 14, programmed : 75000, actual : 0 Timer : 15, programmed : 80000, actual : 0 SimpleTimer : 2, ms : 60315, Dms : 10062 Timer : 0, programmed : 5000, actual : 5000 Timer : 1, programmed : 10000, actual : 10000 Timer : 2, programmed : 15000, actual : 15000 Timer : 3, programmed : 20000, actual : 20000 Timer : 4, programmed : 25000, actual : 25000 Timer : 5, programmed : 30000, actual : 30000 Timer : 6, programmed : 35000, actual : 35017 Timer : 7, programmed : 40000, actual : 40017 Timer : 8, programmed : 45000, actual : 45017 Timer : 9, programmed : 50000, actual : 50017 Timer : 10, programmed : 55000, actual : 55017 Timer : 11, programmed : 60000, actual : 60017 Timer : 12, programmed : 65000, actual : 0 Timer : 13, programmed : 70000, actual : 0 Timer : 14, programmed : 75000, actual : 0 Timer : 15, programmed : 80000, actual : 0 SimpleTimer : 2, ms : 70377, Dms : 10062 Timer : 0, programmed : 5000, actual : 5000 Timer : 1, programmed : 10000, actual : 9996 Timer : 2, programmed : 15000, actual : 15000 Timer : 3, programmed : 20000, actual : 20000 Timer : 4, programmed : 25000, actual : 25000 Timer : 5, programmed : 30000, actual : 30000 Timer : 6, programmed : 35000, actual : 34996 Timer : 7, programmed : 40000, actual : 40017 Timer : 8, programmed : 45000, actual : 45017 Timer : 9, programmed : 50000, actual : 50017 Timer : 10, programmed : 55000, actual : 55017 Timer : 11, programmed : 60000, actual : 60017 Timer : 12, programmed : 65000, actual : 65013 Timer : 13, programmed : 70000, actual : 70013 Timer : 14, programmed : 75000, actual : 0 Timer : 15, programmed : 80000, actual : 0 SimpleTimer : 2, ms : 80440, Dms : 10063 Timer : 0, programmed : 5000, actual : 5000 Timer : 1, programmed : 10000, actual : 10000 Timer : 2, programmed : 15000, actual : 14996 Timer : 3, programmed : 20000, actual : 19996 Timer : 4, programmed : 25000, actual : 24996 Timer : 5, programmed : 30000, actual : 30000 Timer : 6, programmed : 35000, actual : 34996 Timer : 7, programmed : 40000, actual : 39996 Timer : 8, programmed : 45000, actual : 45017 Timer : 9, programmed : 50000, actual : 50017 Timer : 10, programmed : 55000, actual : 55017 Timer : 11, programmed : 60000, actual : 60017 Timer : 12, programmed : 65000, actual : 65013 Timer : 13, programmed : 70000, actual : 70013 Timer : 14, programmed : 75000, actual : 75013 Timer : 15, programmed : 80000, actual : 80013

Debug

Debug is enabled by default on Serial.

You can also change the debugging level from 0 to 3

// 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

Troubleshooting

If you get compilation errors, more often than not, you may need to install a newer version of the core for Arduino boards.

Sometimes, the library will only work if you update the board core to the latest version because I am using newly added functions.

Issues

Submit issues to: megaAVR_TimerInterrupt issues

TO DO

Search for bug and improvement.

DONE

Longer Interval for timers.
Reduce code size if use less timers. Eliminate compiler warnings.
Now supporting complex object pointer-type argument.
16 hardware-initiated software-enabled timers while using only 1 hardware timer.
Fix some bugs in v1.0.0
Add more examples.
Similar library for ESP32, ESP8266, SAMD21/SAMD51, nRF52, Mbed-OS Nano-33-BLE, STM32
Add support to ATmega4809-based boards, such as Arduino UNO WiFi Rev2, AVR_NANO_EVERY, etc.
Selectable TCB Clock 16MHz, 8MHz or 250KHz depending on necessary accuracy
Fix multiple-definitions linker error
Optimize library code by using reference-passing instead of value-passing
Add support to MegaCoreX core, including ATmega4809, ATmega4808, ATmega3209, ATmega3208, ATmega1609, ATmega1608, ATmega809 and ATmega808
Use allman astyle and add utils

Contributions and Thanks

Many thanks for everyone for bug reporting, new feature suggesting, testing and contributing to the development of this library. Especially to these people who have directly or indirectly contributed to this megaAVR_TimerInterrupt library

Thanks to good work of Miguel Wisintainer for initiating, inspriring, working with, developing, debugging, testing and maintaining.
Thanks to Bill Wuttke to report the issue Interrupt interval 2X requested interval #1 leading to new release v1.4.0 to fix bug in using higher frequencies than 250Hz
Thanks to cattledogGH to report the issue Interrupt interval 2X requested interval #1 leading to new release v1.7.0 to fix bug disabling TCB0

_{⭐️ Miguel Wisintainer}

_{Bill Wuttke}

_cattledogGH

Contributing

If you want to contribute to this project:

Report bugs and errors
Ask for enhancements
Create issues and pull requests
Tell other people about this library

License

The library is licensed under MIT

Name		Name	Last commit message	Last commit date
Latest commit History 58 Commits
.github		.github
examples		examples
platformio		platformio
src		src
utils		utils
.codespellrc		.codespellrc
.gitignore		.gitignore
CONTRIBUTING.md		CONTRIBUTING.md
LICENSE		LICENSE
README.md		README.md
changelog.md		changelog.md
keywords.txt		keywords.txt
library.json		library.json
library.properties		library.properties

	#if !( defined(__AVR_ATmega4809__) \|\| defined(ARDUINO_AVR_UNO_WIFI_REV2) \|\| defined(ARDUINO_AVR_NANO_EVERY) \|\| \
	defined(ARDUINO_AVR_ATmega4809) \|\| defined(ARDUINO_AVR_ATmega4808) \|\| defined(ARDUINO_AVR_ATmega3209) \|\| \
	defined(ARDUINO_AVR_ATmega3208) \|\| defined(ARDUINO_AVR_ATmega1609) \|\| defined(ARDUINO_AVR_ATmega1608) \|\| \
	defined(ARDUINO_AVR_ATmega809) \|\| defined(ARDUINO_AVR_ATmega808) )
	#error This is designed only for Arduino or MegaCoreX 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_ 3

	// Select USING_16MHZ == true for 16MHz to Timer TCBx => shorter timer, but better accuracy
	// Select USING_8MHZ == true for 8MHz to Timer TCBx => shorter timer, but better accuracy
	// Select USING_250KHZ == true for 250KHz to Timer TCBx => shorter timer, but better accuracy
	// Not select for default 250KHz to Timer TCBx => longer timer, but worse accuracy
	#define USING_16MHZ true
	#define USING_8MHZ false
	#define USING_250KHZ false


	#define USE_TIMER_0 false
	#define USE_TIMER_1 true
	#define USE_TIMER_2 false
	#define USE_TIMER_3 false

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

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

	#include <SimpleTimer.h> // https://github.com/jfturcot/SimpleTimer

	#ifndef LED_BUILTIN
	#define LED_BUILTIN 13
	#endif

	ISR_Timer ISR_Timer1;

	#define LED_TOGGLE_INTERVAL_MS 1000L

	// You have to use longer time here if having problem because Arduino AVR clock is low, 16MHz => lower accuracy.
	// Tested OK with 1ms when not much load => higher accuracy.
	#define TIMER1_INTERVAL_MS 5L

	volatile uint32_t startMillis = 0;

	void TimerHandler1()
	{
	static bool toggle = false;
	static int timeRun = 0;

	ISR_Timer1.run();

	// Toggle LED every LED_TOGGLE_INTERVAL_MS = 2000ms = 2s
	if (++timeRun == ((LED_TOGGLE_INTERVAL_MS) / TIMER1_INTERVAL_MS) )
	{
	timeRun = 0;

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

	/////////////////////////////////////////////////

	#define NUMBER_ISR_TIMERS 16

	typedef void (*irqCallback) (void);

	/////////////////////////////////////////////////

	#define USE_COMPLEX_STRUCT true

	#if USE_COMPLEX_STRUCT

	typedef struct
	{
	irqCallback irqCallbackFunc;
	uint32_t TimerInterval;
	unsigned long deltaMillis;
	unsigned long previousMillis;
	} ISRTimerData;

	// In NRF52, avoid doing something fancy in ISR, for example Serial.print()
	// The pure simple Serial.prints here are just for demonstration and testing. Must be eliminate in working environment
	// Or you can get this run-time error / crash

	void doingSomething(int index);

	#else

	volatile unsigned long deltaMillis [NUMBER_ISR_TIMERS] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
	volatile unsigned long previousMillis [NUMBER_ISR_TIMERS] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };

	// You can assign any interval for any timer here, in milliseconds
	uint32_t TimerInterval[NUMBER_ISR_TIMERS] =
	{
	5000L, 10000L, 15000L, 20000L, 25000L, 30000L, 35000L, 40000L,
	45000L, 50000L, 55000L, 60000L, 65000L, 70000L, 75000L, 80000L
	};

	void doingSomething(int index)
	{
	unsigned long currentMillis = millis();

	deltaMillis[index] = currentMillis - previousMillis[index];
	previousMillis[index] = currentMillis;
	}

	#endif

	////////////////////////////////////
	// Shared
	////////////////////////////////////

	void doingSomething0()
	{
	doingSomething(0);
	}

	void doingSomething1()
	{
	doingSomething(1);
	}

	void doingSomething2()
	{
	doingSomething(2);
	}

	void doingSomething3()
	{
	doingSomething(3);
	}

	void doingSomething4()
	{
	doingSomething(4);
	}

	void doingSomething5()
	{
	doingSomething(5);
	}

	void doingSomething6()
	{
	doingSomething(6);
	}

	void doingSomething7()
	{
	doingSomething(7);
	}

	void doingSomething8()
	{
	doingSomething(8);
	}

	void doingSomething9()
	{
	doingSomething(9);
	}

	void doingSomething10()
	{
	doingSomething(10);
	}

	void doingSomething11()
	{
	doingSomething(11);
	}

	void doingSomething12()
	{
	doingSomething(12);
	}

	void doingSomething13()
	{
	doingSomething(13);
	}

	void doingSomething14()
	{
	doingSomething(14);
	}

	void doingSomething15()
	{
	doingSomething(15);
	}

	#if USE_COMPLEX_STRUCT

	ISRTimerData curISRTimerData[NUMBER_ISR_TIMERS] =
	{
	//irqCallbackFunc, TimerInterval, deltaMillis, previousMillis
	{ doingSomething0, 5000L, 0, 0 },
	{ doingSomething1, 10000L, 0, 0 },
	{ doingSomething2, 15000L, 0, 0 },
	{ doingSomething3, 20000L, 0, 0 },
	{ doingSomething4, 25000L, 0, 0 },
	{ doingSomething5, 30000L, 0, 0 },
	{ doingSomething6, 35000L, 0, 0 },
	{ doingSomething7, 40000L, 0, 0 },
	{ doingSomething8, 45000L, 0, 0 },
	{ doingSomething9, 50000L, 0, 0 },
	{ doingSomething10, 55000L, 0, 0 },
	{ doingSomething11, 60000L, 0, 0 },
	{ doingSomething12, 65000L, 0, 0 },
	{ doingSomething13, 70000L, 0, 0 },
	{ doingSomething14, 75000L, 0, 0 },
	{ doingSomething15, 80000L, 0, 0 }
	};

	void doingSomething(int index)
	{
	unsigned long currentMillis = millis();

	curISRTimerData[index].deltaMillis = currentMillis - curISRTimerData[index].previousMillis;
	curISRTimerData[index].previousMillis = currentMillis;
	}

	#else

	irqCallback irqCallbackFunc[NUMBER_ISR_TIMERS] =
	{
	doingSomething0, doingSomething1, doingSomething2, doingSomething3,
	doingSomething4, doingSomething5, doingSomething6, doingSomething7,
	doingSomething8, doingSomething9, doingSomething10, doingSomething11,
	doingSomething12, doingSomething13, doingSomething14, doingSomething15
	};

	#endif

	////////////////////////////////////////////////


	#define SIMPLE_TIMER_MS 2000L

	// Init SimpleTimer
	SimpleTimer simpleTimer;

	// Here is software Timer, you can do somewhat fancy stuffs without many issues.
	// But always avoid
	// 1. Long delay() it just doing nothing and pain-without-gain wasting CPU power.Plan and design your code / strategy ahead
	// 2. Very long "do", "while", "for" loops without predetermined exit time.
	void simpleTimerDoingSomething2s()
	{
	static unsigned long previousMillis = startMillis;

	unsigned long currMillis = millis();

	Serial.print(F("SimpleTimer : "));
	Serial.print(SIMPLE_TIMER_MS / 1000);
	Serial.print(F(", ms : "));
	Serial.print(currMillis);
	Serial.print(F(", Dms : "));
	Serial.println(currMillis - previousMillis);

	for (uint16_t i = 0; i < NUMBER_ISR_TIMERS; i++)
	{
	#if USE_COMPLEX_STRUCT
	Serial.print(F("Timer : "));
	Serial.print(i);
	Serial.print(F(", programmed : "));
	Serial.print(curISRTimerData[i].TimerInterval);
	Serial.print(F(", actual : "));
	Serial.println(curISRTimerData[i].deltaMillis);
	#else
	Serial.print(F("Timer : "));
	Serial.print(i);
	Serial.print(F(", programmed : "));
	Serial.print(TimerInterval[i]);
	Serial.print(F(", actual : "));
	Serial.println(deltaMillis[i]);
	#endif
	}

	previousMillis = currMillis;
	}

	void setup()
	{
	pinMode(LED_BUILTIN, OUTPUT);

	Serial.begin(115200);

	while (!Serial);

	Serial.print(F("\nStarting ISR_16_Timers_Array_Complex on "));
	Serial.println(BOARD_NAME);
	Serial.println(MEGA_AVR_TIMER_INTERRUPT_VERSION);
	Serial.print(F("CPU Frequency = "));
	Serial.print(F_CPU / 1000000);
	Serial.println(F(" MHz"));

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

	#if USING_16MHZ
	Serial.println(F("16MHz for highest accuracy"));
	#elif USING_8MHZ
	Serial.println(F("8MHz for very high accuracy"));
	#else
	Serial.println(F("250KHz for lower accuracy but longer time"));
	#endif

	ITimer1.init();

	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"));

	//ISR_Timer1.setInterval(2000L, doingSomething2s);
	//ISR_Timer1.setInterval(5000L, doingSomething5s);

	// Just to demonstrate, don't use too many ISR Timers if not absolutely necessary
	// You can use up to 16 timer for each ISR_Timer
	for (uint16_t i = 0; i < NUMBER_ISR_TIMERS; i++)
	{
	#if USE_COMPLEX_STRUCT
	curISRTimerData[i].previousMillis = startMillis;
	ISR_Timer1.setInterval(curISRTimerData[i].TimerInterval, curISRTimerData[i].irqCallbackFunc);
	#else
	previousMillis[i] = startMillis;
	ISR_Timer1.setInterval(TimerInterval[i], irqCallbackFunc[i]);
	#endif
	}

	// You need this timer for non-critical tasks. Avoid abusing ISR if not absolutely necessary.
	simpleTimer.setInterval(SIMPLE_TIMER_MS, simpleTimerDoingSomething2s);
	}

	#define BLOCKING_TIME_MS 10000L

	void loop()
	{
	// This unadvised blocking task is used to demonstrate the blocking effects onto the execution and accuracy to Software timer
	// You see the time elapse of ISR_Timer still accurate, whereas very unaccurate for Software Timer
	// The time elapse for 2000ms software timer now becomes 3000ms (BLOCKING_TIME_MS)
	// While that of ISR_Timer is still prefect.
	delay(BLOCKING_TIME_MS);

	// You need this Software timer for non-critical tasks. Avoid abusing ISR if not absolutely necessary
	// You don't need to and never call ISR_Timer.run() here in the loop(). It's already handled by ISR timer.
	simpleTimer.run();
	}

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megaAVR_TimerInterrupt Library

Table of Contents

Important Change from v1.5.0

Why do we need this megaAVR_TimerInterrupt library

Features

Why using ISR-based Hardware Timer Interrupt is better

Important Notes about ISR

Currently supported Boards

Prerequisites

Installation

Use Arduino Library Manager

Manual Install

VS Code & PlatformIO:

HOWTO Fix Multiple Definitions Linker Error

More useful Information

1. Documents

2. Timer TCB0-TCB3

Usage

1. Using only Hardware Timer directly

1.1 Init Hardware Timer

1.2 Set Hardware Timer Interval and attach Timer Interrupt Handler function

1.3 Set Hardware Timer Frequency and attach Timer Interrupt Handler function

2. Using 16 ISR_based Timers from 1 Hardware Timer

2.1 Important Note

2.2 Init Hardware Timer and ISR-based Timer

2.3 Set Hardware Timer Interval and attach Timer Interrupt Handler functions

Examples:

Example ISR_16_Timers_Array_Complex

Debug Terminal Output Samples

1. ISR_16_Timers_Array_Complex on Arduino megaAVR Nano Every

2. Change_Interval on Arduino megaAVR Nano Every

3. ISR_16_Timers_Array_Complex on Arduino megaAVR Nano Every to show accuracy difference.

3.1. TCB Clock Frequency 16MHz for highest accuracy

3.2. TCB Clock Frequency 8MHz for very high accuracy

3.3. TCB Clock Frequency 250KHz for lower accuracy but longer time

4. Change_Interval_HF on Arduino megaAVR Nano Every

5. ISR_16_Timers_Array_Complex on Arduino megaAVR Nano Every using MegaCoreX

Debug

Troubleshooting

Issues

TO DO

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