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This library enables you to use Interrupt from Hardware Timers on Arduino AVR ATtiny-based boards (ATtiny3217, etc.) using megaTinyCore. These ATtiny 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 …

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ATtiny_TimerInterrupt Library

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Table of Contents

Important Note for Arduino IDE

With some Arduino IDE versions, such as v1.8.19, upload directly via USB to some boards, such as AVR_CuriosityNano3217 can't be done without unknown-to-me fix. We'll get the following error when uploading

avrdude: Version 6.3-20201216 Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/ Copyright (c) 2007-2014 Joerg Wunsch System wide configuration file is "/home/kh/.arduino15/packages/megaTinyCore/hardware/megaavr/2.5.11/avrdude.conf" User configuration file is "/home/kh/.avrduderc" User configuration file does not exist or is not a regular file, skipping Using Port : usb Using Programmer : curiosity_updi avrdude: usbdev_open(): Found nEDBG CMSIS-DAP, serno: MCHP3333021800000998 avrdude: usbdev_open(): WARNING: failed to set configuration 1: Device or resource busy avrdude: Found CMSIS-DAP compliant device, using EDBG protocol avrdude: usbdev_send(): wrote -5 out of 912 bytes, err = Input/output error avrdude: jtag3_edbg_prepare(): failed to send command to serial port avrdude done. Thank you. the selected serial port does not exist or your board is not connected

We can use drag-and-drop method to drag-and-drop the compiled hex file to CURIOSITY virtual drive.

If success, The LED blinks slowly for 2 sec. The LED will blinks rapidly for 2 sec if failure

For example, to run Change_Interval example, use Arduino IDE to compile, and get the Change_Interval.ino.hex file. For Ubuntu Linux, the file is stored in directory /tmp/arduino_build_xxxxxx

After drag-and-drop the Change_Interval.ino.hex into CURIOSITY virtual drive, the code will run immediately if successfully loaded (LED blinks slowly)

Why do we need this ATtiny_TimerInterrupt library

Features

This library enables you to use Interrupt from Hardware Timers on Arduino AVR ATtiny-based boards (ATtiny3217, etc.) using using megaTinyCore

As Hardware Timers are rare, and very precious assets of any board, this library now enables you to use up to 16 ISR-based Timers, while consuming only 1 Hardware Timer. Timers' interval is very long (uint64_t millisecs).

Now with these new 16 ISR-based timers, the maximum interval is practically unlimited (limited only by uint64_t milliseconds) while 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, such as connecting to WiFi, Internet and Blynk services. This important feature is absolutely necessary for mission-critical tasks. You can also have many (up to 16) timers to use.

This non-being-blocked important feature is absolutely necessary for mission-critical tasks.

The ISR_16_Timers_Array_Complex example will demonstrate the nearly perfect accuracy compared to software timers by printing the actual elapsed millisecs of each type of timers.

You'll see blynkTimer Software is blocked while system is connecting to WiFi / Internet / Blynk, as well as by blocking task in loop(), using delay() function as an example. The elapsed time then is very unaccurate

Why using ISR-based Hardware Timer Interrupt is better

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

  1. 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.

  2. 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

  • tinyAVR boards using megaTinyCore
Curiosity Nano ATtiny3217

Prerequisites

  1. Arduino IDE 1.8.19+ for Arduino. GitHub release
  2. SpenceKonde megaTinyCore core 2.5.11+ for Arduino ATtiny boards. GitHub release. Follow megaTinyCore Installation.
  3. To use with certain example

Installation

Use Arduino Library Manager

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

Manual Install

Another way to install is to:

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

VS Code & PlatformIO:

  1. Install VS Code
  2. Install PlatformIO
  3. Install ATtiny_TimerInterrupt library by using Library Manager. Search for ATtiny_TimerInterrupt in Platform.io Author's Libraries
  4. 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 "ATtiny_TimerInterrupt.hpp" //https://github.com/khoih-prog/ATtiny_TimerInterrupt // Can be included as many times as necessary, without `Multiple Definitions` Linker Error #include "ATtiny_ISR_Timer.hpp" //https://github.com/khoih-prog/ATtiny_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 "ATtiny_TimerInterrupt.h" //https://github.com/khoih-prog/ATtiny_TimerInterrupt // To be included only in main(), .ino with setup() to avoid `Multiple Definitions` Linker Error #include "ATtiny_ISR_Timer.h" //https://github.com/khoih-prog/ATtiny_TimerInterrupt

Check the new multiFileProject example for a HOWTO demo.

More useful Information

1. Documents

  1. Arduino 101: Timers and Interrupts
  2. Getting Started with Timer/Counter Type B (TCB)
  3. megaTinyCore README.md
  4. ATtiny3217 Curiosity Nano Hardware User Guide
  5. AVR128DA48-Curiosity-Nano-Hardware-User Guide
  6. AVR128DB48-Curiosity-Nano-Hardware-User Guide

2. Timer TCB0-TCB1

TCB0-TCB1 are 16-bit timers

The ATtiny boards, such as ATtiny3217, ATtiny1617, will have only maximum 2 TCB timers, (TCB0-TCB1).

The ATtiny boards, such as ATtiny817, will have only maximum 1 TCB timer, (TCB0).

The number of TCB timers will be automatically configured by the library.

The following is the partial list of number of TCBs for each ATtiny board/chip

TCB0-TCB1, TCA, TCD

ATtiny3217, ATtiny1617, ATtiny3216, ATtiny1616, ATtiny1614

TCB0, TCA, TCD

ATtinyx12, ATtinyx14, ATtinyx16, ATtinyx17, such as ATtiny817, ATtiny417, ATtiny816, etc.

TCB0, TCA, no TCD

ATtinyx02, ATtinyx04, ATtinyx06, ATtinyx07, such as ATtiny1607, ATtiny807, ATtiny1606, etc.

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_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 // Init timer CurrentTimer CurrentTimer.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 ITimer1.init(); if (ITimer1.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")); }

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)) { SerialDebug.print(F("Starting ITimer OK, millis() = ")); SerialDebug.println(millis()); } else SerialDebug.println("Can't set ITimer. 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

// 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 // 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 SerialDebug.print with String() argument // The pure simple SerialDebug.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() { .... // Timer TCB2 is used for micros(), millis(), delay(), etc and can't be used CurrentTimer.init(); // Interval in millisecs if (CurrentTimer.attachInterruptInterval(HW_TIMER_INTERVAL_MS, TimerHandler)) { lastMillis = millis(); SerialDebug.print(F("Starting ITimer OK, millis() = ")); SerialDebug.println(millis()); } else SerialDebug.println(F("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:

  1. Argument_Complex
  2. Argument_None
  3. Argument_Simple
  4. Change_Interval.
  5. FakeAnalogWrite.
  6. ISR_16_Timers_Array_Complex.
  7. ISR_RPM_Measure
  8. Change_Interval_HF
  9. ISR_Timers_Array_Simple.
  10. RPM_Measure
  11. SwitchDebounce
  12. TimerDuration
  13. TimerInterruptTest
  14. multiFileProject

Example ISR_16_Timers_Array_Complex

ATtiny_TimerInterrupt/examples/ISR_16_Timers_Array_Complex/ISR_16_Timers_Array_Complex.ino

Lines 16 to 376 in e844b26

// 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"
// To be included only in main(), .ino with setup() to avoid `Multiple Definitions` Linker Error
#include "ATtiny_ISR_Timer.h"
#include <SimpleTimer.h> // https://github.com/jfturcot/SimpleTimer
#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
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) ();
/////////////////////////////////////////////////
#define USE_COMPLEX_STRUCT true
#if USE_COMPLEX_STRUCT
typedef struct
{
irqCallback irqCallbackFunc;
uint32_t TimerInterval;
unsigned long deltaMillis;
unsigned long previousMillis;
} ISRTimerData;
// Avoid doing something fancy in ISR, for example SerialDebug.print()
// The pure simple SerialDebug.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();
SerialDebug.print(F("SimpleTimer : "));SerialDebug.print(SIMPLE_TIMER_MS / 1000);
SerialDebug.print(F(", ms : ")); SerialDebug.print(currMillis);
SerialDebug.print(F(", Dms : ")); SerialDebug.println(currMillis - previousMillis);
for (uint16_t i = 0; i < NUMBER_ISR_TIMERS; i++)
{
#if USE_COMPLEX_STRUCT
SerialDebug.print(F("Timer : ")); SerialDebug.print(i);
SerialDebug.print(F(", programmed : ")); SerialDebug.print(curISRTimerData[i].TimerInterval);
SerialDebug.print(F(", actual : ")); SerialDebug.println(curISRTimerData[i].deltaMillis);
#else
SerialDebug.print(F("Timer : ")); SerialDebug.print(i);
SerialDebug.print(F(", programmed : ")); SerialDebug.print(TimerInterval[i]);
SerialDebug.print(F(", actual : ")); SerialDebug.println(deltaMillis[i]);
#endif
}
previousMillis = currMillis;
}
void setup()
{
pinMode(LED_BUILTIN, OUTPUT);
SerialDebug.begin(115200);
while (!SerialDebug && millis() < 5000);
SerialDebug.print(F("\nStarting ISR_16_Timers_Array_Complex 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"));
//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 AVR_CuriosityNano3217

The following is the sample terminal output when running example ISR_16_Timers_Array_Complex on AVR_CuriosityNano3217 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 AVR_CuriosityNano3217 ATtiny_TimerInterrupt v1.0.1 CPU Frequency = 20 MHz TCB Clock Frequency = Full clock (20/16MHz, etc) for highest accuracy Starting ITimer OK, millis() = 13 SimpleTimer : 2, ms : 9949, Dms : 9949 Timer : 0, programmed : 5000, actual : 5015 Timer : 1, programmed : 10000, actual : 0 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 : 19876, Dms : 9927 Timer : 0, programmed : 5000, actual : 5000 Timer : 1, programmed : 10000, actual : 10016 Timer : 2, programmed : 15000, actual : 15016 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 : 179959, Dms : 9997 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 : 29996 Timer : 6, programmed : 35000, actual : 35000 Timer : 7, programmed : 40000, actual : 39996 Timer : 8, programmed : 45000, actual : 45001 Timer : 9, programmed : 50000, actual : 49997 Timer : 10, programmed : 55000, actual : 54996 Timer : 11, programmed : 60000, actual : 60001 Timer : 12, programmed : 65000, actual : 64997 Timer : 13, programmed : 70000, actual : 69997 Timer : 14, programmed : 75000, actual : 74997 Timer : 15, programmed : 80000, actual : 79997

2. ISR_16_Timers_Array_Complex on AVR_CuriosityNano3217 to show accuracy difference

2.1. TCB Clock Frequency Full clock for highest accuracy

Starting ISR_16_Timers_Array_Complex on AVR_CuriosityNano3217 ATtiny_TimerInterrupt v1.0.1 CPU Frequency = 20 MHz TCB Clock Frequency = Full clock (20/16MHz, etc) for highest accuracy Starting ITimer OK, millis() = 13 SimpleTimer : 2, ms : 9949, Dms : 9949 Timer : 0, programmed : 5000, actual : 5015 Timer : 1, programmed : 10000, actual : 0 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 : 19876, Dms : 9927 Timer : 0, programmed : 5000, actual : 5000 Timer : 1, programmed : 10000, actual : 10016 Timer : 2, programmed : 15000, actual : 15016 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 : 179959, Dms : 9997 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 : 29996 Timer : 6, programmed : 35000, actual : 35000 Timer : 7, programmed : 40000, actual : 39996 Timer : 8, programmed : 45000, actual : 45001 Timer : 9, programmed : 50000, actual : 49997 Timer : 10, programmed : 55000, actual : 54996 Timer : 11, programmed : 60000, actual : 60001 Timer : 12, programmed : 65000, actual : 64997 Timer : 13, programmed : 70000, actual : 69997 Timer : 14, programmed : 75000, actual : 74997 Timer : 15, programmed : 80000, actual : 79997

2.2. TCB Clock Frequency Half clock for high accuracy

Starting ISR_16_Timers_Array_Complex on AVR_CuriosityNano3217 ATtiny_TimerInterrupt v1.0.1 CPU Frequency = 20 MHz TCB Clock Frequency = Half clock (10/8MHz, etc.) for high accuracy Starting ITimer OK, millis() = 13 SimpleTimer : 2, ms : 9752, Dms : 9752 Timer : 0, programmed : 5000, actual : 5015 Timer : 1, programmed : 10000, actual : 0 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 : 19810, Dms : 10058 Timer : 0, programmed : 5000, actual : 5000 Timer : 1, programmed : 10000, actual : 10016 Timer : 2, programmed : 15000, actual : 15016 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 : 89713, Dms : 9998 Timer : 0, programmed : 5000, actual : 5000 Timer : 1, programmed : 10000, actual : 10001 Timer : 2, programmed : 15000, actual : 15001 Timer : 3, programmed : 20000, actual : 20001 Timer : 4, programmed : 25000, actual : 25001 Timer : 5, programmed : 30000, actual : 30000 Timer : 6, programmed : 35000, actual : 35000 Timer : 7, programmed : 40000, actual : 40001 Timer : 8, programmed : 45000, actual : 45017 Timer : 9, programmed : 50000, actual : 50016 Timer : 10, programmed : 55000, actual : 55017 Timer : 11, programmed : 60000, actual : 60016 Timer : 12, programmed : 65000, actual : 65017 Timer : 13, programmed : 70000, actual : 70016 Timer : 14, programmed : 75000, actual : 75017 Timer : 15, programmed : 80000, actual : 80017

3. Change_Interval_HF on AVR_CuriosityNano3217

The following is the sample terminal output when running example Change_Interval_HF on AVR_CuriosityNano3217 to demonstrate how to change High Frequency Timer Interval on-the-fly

Starting Change_Interval_HF on AVR_CuriosityNano3217 ATtiny_TimerInterrupt v1.0.1 CPU Frequency = 20 MHz TCB Clock Frequency = Full clock (20/16MHz, etc) for highest accuracy Starting ITimer OK, millis() = 13 Frequency, Timer = 50 Time = 1001, Timer1Count = 49 Time = 2002, Timer1Count = 99 Time = 3003, Timer1Count = 149 Time = 4004, Timer1Count = 199 Time = 5005, Timer1Count = 249 Changing Frequency, Timer = 25 Time = 6006, Timer1Count = 274 Time = 7007, Timer1Count = 299 Time = 8008, Timer1Count = 324 Time = 9009, Timer1Count = 349 Time = 10010, Timer1Count = 374 Changing Frequency, Timer = 16 Time = 11011, Timer1Count = 390 Time = 12012, Timer1Count = 406 Time = 13013, Timer1Count = 422 Time = 14014, Timer1Count = 438 Time = 15015, Timer1Count = 454 Changing Frequency, Timer = 12 Time = 16016, Timer1Count = 466 Time = 17017, Timer1Count = 478 Time = 18018, Timer1Count = 490 Time = 19019, Timer1Count = 502 Time = 20020, Timer1Count = 514 Changing Frequency, Timer = 10 Time = 21021, Timer1Count = 524 Time = 22022, Timer1Count = 534 Time = 23023, Timer1Count = 544 Time = 24024, Timer1Count = 554 Time = 25025, Timer1Count = 564

Debug

Debug is enabled by default on Serial for AVR_CuriosityNano3217.

You can also change the debugging level from 0 to 4

// These define's must be placed at the beginning before #include "ATtiny_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: ATtiny_TimerInterrupt issues

TO DO

  1. Search for bug and improvement
  2. Add support to 250KHz Timer Frequency

DONE

  1. Longer Interval for timers
  2. Reduce code size if use less timers. Eliminate compiler warnings
  3. Now supporting complex object pointer-type argument
  4. 16 hardware-initiated software-enabled timers while using only 1 hardware timer
  5. Add support to ATtiny-based boards (AVR_CuriosityNano3217, etc.) using megaTinyCore
  6. Selectable TCB Clock FULL, HALF depending on necessary accuracy
  7. Fix multiple-definitions linker error
  8. Optimize library code by using reference-passing instead of value-passing
  9. Improve and customize examples for AVR_CuriosityNano3217 boards to use on-board LED and SW
  10. Add notes howto upload by drag-and-drop to CURIOSITY virtual drive
  11. Using Serial for debugging with AVR_CuriosityNano3217
  12. Default to use TCB0 in examples for boards having only 1 TCB Timer, such as ATtiny817, ATtiny807
  13. Fix bug giving error when using TCB0 (USE_TIMER_0 == true)

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 ATtiny_TimerInterrupt library

  1. Thanks to good work of Spence Konde (aka Dr. Azzy) for the megaTinyCore
  2. Thanks to LaurentR59 to request the enhancement Support for DX CORE CPU and MightyCORE CPU possible? #8 leading to this new library
SpenceKonde
⭐️⭐️ Spence Konde
 LaurentR59
LaurentR59

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

Copyright

Copyright (c) 2022- Khoi Hoang

About

This library enables you to use Interrupt from Hardware Timers on Arduino AVR ATtiny-based boards (ATtiny3217, etc.) using megaTinyCore. These ATtiny 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 …

Topics

attiny timer accuracy isr non-blocking timer-interrupt mission-critical attiny3217 megaavr hardware-timers curiosity-nano-board megatinycore tcb-timers at-tiny attiny16 attiny32 attiny8 attiny4 attiny-timerinterrupt curiosity-nano-attiny3217

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v1.0.1 to fix bug giving error when using TCB0 and default to use TCB0 in examples for boards having only 1 TCB Timer, such as `ATtiny817`, `ATtiny807` Latest
Aug 27, 2022
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