khoih-prog / SAMD_TimerInterrupt

SAMD_TimerInterrupt Library

Important Change from v1.6.0
Why do we need this SAMD_TimerInterrupt library
- Features
- Why using ISR-based Hardware Timer Interrupt is better
- Currently supported Boards
- Important Notes about ISR
Changelog
Prerequisites
Installation
- Use Arduino Library Manager
- Manual Install
- VS Code & PlatformIO
Packages' Patches
- 1. For Arduino SAMD boards
  - For core version v1.8.10+
  - For core version v1.8.9-
- 2. For Adafruit SAMD boards
- 3. For Seeeduino SAMD boards
Libraries' Patches
- 1. For application requiring 2K+ HTML page
- 2. For Ethernet library
- 3. For EthernetLarge library
- 4. For Etherne2 library
- 5. For Ethernet3 library
- 6. For UIPEthernet library
- 7. For fixing ESP32 compile error
HOWTO Fix Multiple Definitions Linker Error
New from v1.0.0
Usage
- 1. Using only Hardware Timer directly
  - 1.1 Init Hardware Timer
  - 1.2 Set Hardware Timer Interval and attach Timer Interrupt Handler function
- 2. Using 16 ISR_based Timers from 1 Hardware Timer
  - 2.1 Init Hardware Timer and ISR-based Timer
  - 2.2 Set Hardware Timer Interval and attach Timer Interrupt Handler functions
Examples
- 1. Argument_None
- 2. Argument_None_uS
- 3. ISR_16_Timers_Array
- 4. ISR_RPM_Measure
- 5. ISR_Timer_Complex_Ethernet
- 6. ISR_Timer_Complex_WiFiNINA
- 7. RPM_Measure
- 8. SwitchDebounce
- 9. TimerInterruptTest
- 10. TimerInterruptLEDDemo
- 11. Change_Interval
- 12. ISR_16_Timers_Array_Complex
- 13. RepeatedAttachInterrupt_uS
- 14. multiFileProject
- 15. SAMD21_MultiTimers New
Example ISR_16_Timers_Array_Complex
Debug Terminal Output Samples
- 1. ISR_Timer_Complex_WiFiNINA on Arduino SAMD21 SAMD_NANO_33_IOT using WiFiNINA
- 2. TimerInterruptTest on Adafruit SAMD51 ITSYBITSY_M4
- 3. Argument_None on Arduino SAMD21 SAMD_NANO_33_IOT
- 4. ISR_16_Timers_Array on Arduino SAMD21 SAMD_NANO_33_IOT
- 5. Change_Interval on Arduino SAMD21 SAMD_NANO_33_IOT
- 6. RepeatedAttachInterrupt_uS on SAMD21 SEEED_XIAO_M0
- 7. SAMD21_MultiTimers on SAMD21 SAMD_NANO_33_IOT
Debug
Troubleshooting
Issues
TO DO
DONE
Contributions and Thanks
Contributing
License
Copyright

Important Change from v1.6.0

Please have a look at HOWTO Fix Multiple Definitions Linker Error

Why do we need this SAMD_TimerInterrupt library

Features

This library enables you to use Interrupt from Hardware Timers on an SAMD-based board, such as SAMD21 Nano-33-IoT, Adafruit SAMD51 Itsy-Bitsy M4, SparkFun SAMD51 MicroMod, etc.

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 (ulong millisecs).

Now with these new 16 ISR-based timers, the maximum interval is practically unlimited (limited only by unsigned long 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. This important feature is absolutely necessary for mission-critical tasks.

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

Being ISR-based timers, their executions are not blocked by bad-behaving functions / tasks, such as connecting to WiFi, Internet and Blynk services. You can also have many (up to 16) timers to use.

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

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

Currently supported Boards

Arduino SAMD21 (ZERO, MKR, NANO_33_IOT, etc.).
Adafruit SAM21 (Itsy-Bitsy M0, Metro M0, Feather M0, Gemma M0, etc.).
Adafruit SAM51 (Itsy-Bitsy M4, Metro M4, Grand Central M4, Feather M4 Express, etc.).
Seeeduino SAMD21/SAMD51 boards (SEEED_WIO_TERMINAL, SEEED_FEMTO_M0, SEEED_XIAO_M0, Wio_Lite_MG126, WIO_GPS_BOARD, SEEEDUINO_ZERO, SEEEDUINO_LORAWAN, SEEED_GROVE_UI_WIRELESS, etc.)
Sparkfun SAMD21 boards such as SparkFun_RedBoard_Turbo, SparkFun_Qwiic_Micro, etc.
Sparkfun SAMD51 boards such as SparkFun_SAMD51_Thing_Plus, SparkFun_SAMD51_MicroMod, etc.

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.
The maximum time you can use directly on SAMD TC3/TCC Timer is ~1398.11ms = 1.39811s. If you use time larger than 1398.11ms, the wrap-around will happen and you'll get much smaller time.

Prerequisites

Arduino IDE 1.8.19+ for Arduino.
Arduino SAMD core 1.8.13+ for SAMD ARM Cortex-M0+ boards.
Adafruit SAMD core 1.7.11+ for SAMD ARM Cortex-M0+ and M4 boards (Nano 33 IoT, etc.).
Seeeduino SAMD core 1.8.3+ for SAMD21/SAMD51 boards (XIAO M0, Wio Terminal, etc.).
Sparkfun SAMD core 1.8.7+ for SAMD21/SAMD51 boards (SparkFun_RedBoard_Turbo, SparkFun_SAMD51_Thing_Plus, etc.).
Blynk library 1.1.0. to use with some examples. Don't use Blynk beta versions.
To use with some examples, depending on which Ethernet card you're using:

Ethernet_Generic library v2.7.1+ for W5100, W5200 and W5500/WIZ550io/WIZ850io/USR-ES1 with Wiznet W5500 chip.
EthernetENC library v2.0.3+ for ENC28J60. . New and Better
UIPEthernet library v2.0.12+ for ENC28J60.

To use with some examples

SimpleTimer library for ISR_16_Timers_Array and ISR_16_Timers_Array_Complex examples. New to avoid error with old Sparkfun core.

Installation

Use Arduino Library Manager

The best and easiest way is to use Arduino Library Manager. Search for SAMD_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 SAMD_TimerInterrupt page.
Download the latest release SAMD_TimerInterrupt-master.zip.
Extract the zip file to SAMD_TimerInterrupt-master directory
Copy whole SAMD_TimerInterrupt-master folder to Arduino libraries' directory such as ~/Arduino/libraries/.

VS Code & PlatformIO

Install VS Code
Install PlatformIO
Install SAMD_TimerInterrupt library by using Library Manager. Search for SAMD_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

Packages' Patches

1. For Arduino SAMD boards

To be able to compile, run and automatically detect and display BOARD_NAME on Arduino SAMD (Nano-33-IoT, etc) boards, you have to copy the whole Arduino SAMD Packages_Patches directory into Arduino SAMD directory (~/.arduino15/packages/arduino/hardware/samd/1.8.13).

For core version v1.8.10+

Supposing the Arduino SAMD version is 1.8.13. Now only one file must be copied into the directory:

~/.arduino15/packages/arduino/hardware/samd/1.8.13/platform.txt

Whenever a new version is installed, remember to copy this files into the new version directory. For example, new version is x.yy.zz

This file must be copied into the directory:

~/.arduino15/packages/arduino/hardware/samd/x.yy.zz/platform.txt

For core version v1.8.9-

Supposing the Arduino SAMD version is 1.8.9. These files must be copied into the directory:

~/.arduino15/packages/arduino/hardware/samd/1.8.9/platform.txt
~/.arduino15/packages/arduino/hardware/samd/1.8.9/cores/arduino/Arduino.h

Whenever a new version is installed, remember to copy these files into the new version directory. For example, new version is x.yy.z

These files must be copied into the directory:

~/.arduino15/packages/arduino/hardware/samd/x.yy.z/platform.txt
~/.arduino15/packages/arduino/hardware/samd/x.yy.z/cores/arduino/Arduino.h

This is mandatory to fix the notorious Arduino SAMD compiler error. See Improve Arduino compatibility with the STL (min and max macro)

 ...\arm-none-eabi\include\c++\7.2.1\bits\stl_algobase.h:243:56: error: macro "min" passed 3 arguments, but takes just 2
     min(const _Tp& __a, const _Tp& __b, _Compare __comp)

Whenever the above-mentioned compiler error issue is fixed with the new Arduino SAMD release, you don't need to copy the Arduino.h file anymore.

2. For Adafruit SAMD boards

To be able to compile, run and automatically detect and display BOARD_NAME on Adafruit SAMD (Itsy-Bitsy M4, etc) boards, you have to copy the whole Adafruit SAMD Packages_Patches directory into Adafruit samd directory (~/.arduino15/packages/adafruit/hardware/samd/1.7.11).

Supposing the Adafruit SAMD core version is 1.7.11. This file must be copied into the directory:

~/.arduino15/packages/adafruit/hardware/samd/1.7.11/platform.txt
~/.arduino15/packages/adafruit/hardware/samd/1.7.11/cores/arduino/Print.h
~/.arduino15/packages/adafruit/hardware/samd/1.7.11/cores/arduino/Print.cpp

Whenever a new version is installed, remember to copy this file into the new version directory. For example, new version is x.yy.zz This file must be copied into the directory:

~/.arduino15/packages/adafruit/hardware/samd/x.yy.zz/platform.txt
~/.arduino15/packages/adafruit/hardware/samd/x.yy.zz/cores/arduino/Print.h
~/.arduino15/packages/adafruit/hardware/samd/x.yy.zz/cores/arduino/Print.cpp

3. For Seeeduino SAMD boards

To be able to compile, run and automatically detect and display BOARD_NAME on Seeeduino SAMD (XIAO M0, Wio Terminal, etc) boards, you have to copy the whole Seeeduino SAMD Packages_Patches directory into Seeeduino samd directory (~/.arduino15/packages/Seeeduino/hardware/samd/1.8.3).

Supposing the Seeeduino SAMD core version is 1.8.3. This file must be copied into the directory:

~/.arduino15/packages/Seeeduino/hardware/samd/1.8.3/platform.txt
~/.arduino15/packages/Seeeduino/hardware/samd/1.8.3/cores/arduino/Arduino.h
~/.arduino15/packages/Seeeduino/hardware/samd/1.8.3/cores/arduino/Print.h
~/.arduino15/packages/Seeeduino/hardware/samd/1.8.3/cores/arduino/Print.cpp

Whenever a new version is installed, remember to copy this file into the new version directory. For example, new version is x.yy.zz This file must be copied into the directory:

~/.arduino15/packages/Seeeduino/hardware/samd/x.yy.zz/platform.txt
~/.arduino15/packages/Seeeduino/hardware/samd/x.yy.zz/cores/arduino/Arduino.h
~/.arduino15/packages/Seeeduino/hardware/samd/x.yy.zz/cores/arduino/Print.h
~/.arduino15/packages/Seeeduino/hardware/samd/x.yy.zz/cores/arduino/Print.cpp

Libraries' Patches

Notes: These patches are totally optional and necessary only when you use the related Ethernet library and get certain error or issues.

1. For application requiring 2K+ HTML page

If your application requires 2K+ HTML page, the current Ethernet library must be modified if you are using W5200/W5500 Ethernet shields. W5100 is not supported for 2K+ buffer. If you use boards requiring different CS/SS pin for W5x00 Ethernet shield, for example ESP32, ESP8266, nRF52, etc., you also have to modify the following libraries to be able to specify the CS/SS pin correctly.

2. For Ethernet library

To fix Ethernet library, just copy these following files into the Ethernet library directory to overwrite the old files:

3. For EthernetLarge library

To fix EthernetLarge library, just copy these following files into the EthernetLarge library directory to overwrite the old files:

4. For Ethernet2 library

To fix Ethernet2 library, just copy these following files into the Ethernet2 library directory to overwrite the old files:

To add UDP Multicast support, necessary for the UPnP_Generic library:

5. For Ethernet3 library

To fix Ethernet3 library, just copy these following files into the Ethernet3 library directory to overwrite the old files:

6. For UIPEthernet library

To be able to compile and run on nRF52 boards with ENC28J60 using UIPEthernet library, you have to copy these following files into the UIPEthernet utility directory to overwrite the old files:

7. For fixing ESP32 compile error

To fix ESP32 compile error, just copy the following file into the ESP32 cores/esp32 directory (e.g. ./arduino-1.8.12/hardware/espressif/cores/esp32) to overwrite the old file:

Server.h

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 .hpp

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

// Can be included as many times as necessary, without `Multiple Definitions` Linker Error
#include "SAMD_ISR_Timer.hpp"         //https://github.com/khoih-prog/SAMD_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 "SAMDTimerInterrupt.h"       //https://github.com/khoih-prog/SAMD_TimerInterrupt

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

New from v1.0.0

Now with these new 16 ISR-based timers (while consuming only 1 hardware timer), the maximum interval is practically unlimited (limited only by unsigned long milliseconds). The accuracy is nearly perfect compared to software timers. The most important feature is they're ISR-based timers Therefore, their executions are not blocked by bad-behaving functions / tasks. This important feature is absolutely necessary for mission-critical tasks.

The ISR_Timer_Complex example will demonstrate the nearly perfect accuracy compared to software timers by printing the actual elapsed millisecs of each type of timers. Being ISR-based timers, their executions are not blocked by bad-behaving functions / tasks, such as connecting to WiFi, Internet and Blynk services. You can also have many (up to 16) timers to use. This non-being-blocked important feature is absolutely necessary for mission-critical tasks. 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

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 only one to be true for SAMD21. Must must be placed at the beginning before #include "SAMDTimerInterrupt.h"
#define USING_TIMER_TC3         true      // Only TC3 can be used for SAMD51
#define USING_TIMER_TC4         false     // Not to use with Servo library
#define USING_TIMER_TC5         false
#define USING_TIMER_TCC         false
#define USING_TIMER_TCC1        false
#define USING_TIMER_TCC2        false     // Don't use this, can crash on some boards

// Uncomment To test if conflict with Servo library
//#include "Servo.h"

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

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

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

// TC3, TC4, TC5 max permissible TIMER_INTERVAL_MS is 1398.101 ms, larger will overflow, therefore not permitted
// Use TCC, TCC1, TCC2 for longer TIMER_INTERVAL_MS
#define TIMER_INTERVAL_MS        1000

#if USING_TIMER_TC3
  #define SELECTED_TIMER      TIMER_TC3
#elif USING_TIMER_TC4
  #define SELECTED_TIMER      TIMER_TC4
#elif USING_TIMER_TC5
  #define SELECTED_TIMER      TIMER_TC5
#elif USING_TIMER_TCC
  #define SELECTED_TIMER      TIMER_TCC
#elif USING_TIMER_TCC1
  #define SELECTED_TIMER      TIMER_TCC1
#elif USING_TIMER_TCC2
  #define SELECTED_TIMER      TIMER_TCC
#else
  #error You have to select 1 Timer  
#endif

// Init selected SAMD timer
SAMDTimer ITimer(SELECTED_TIMER);

1.2 Set Hardware Timer Interval and attach Timer Interrupt Handler function

void TimerHandler()
{
  // Doing something here inside ISR
}

// TC3, TC4, TC5 max permissible TIMER_INTERVAL_MS is 1398.101 ms, larger will overflow, therefore not permitted
// Use TCC, TCC1, TCC2 for longer TIMER_INTERVAL_MS
#define TIMER_INTERVAL_MS        1000      // 1s = 1000ms

void setup()
{
  ....
  
  // Interval in microsecs
  if (ITimer.attachInterruptInterval_MS(TIMER_INTERVAL_MS, TimerHandler0))
    Serial.println("Starting  ITimer OK, millis() = " + String(millis()));
  else
    Serial.println("Can't set ITimer. Select another freq. or timer");
}

2. Using 16 ISR_based Timers from 1 Hardware Timer

2.1 Init Hardware Timer and ISR-based Timer

// Select only one to be true for SAMD21. Must must be placed at the beginning before #include "SAMDTimerInterrupt.h"
#define USING_TIMER_TC3         true      // Only TC3 can be used for SAMD51
#define USING_TIMER_TC4         false     // Not to use with Servo library
#define USING_TIMER_TC5         false
#define USING_TIMER_TCC         false
#define USING_TIMER_TCC1        false
#define USING_TIMER_TCC2        false     // Don't use this, can crash on some boards

// Uncomment To test if conflict with Servo library
//#include "Servo.h"

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

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

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

// TC3, TC4, TC5 max permissible TIMER_INTERVAL_MS is 1398.101 ms, larger will overflow, therefore not permitted
// Use TCC, TCC1, TCC2 for longer TIMER_INTERVAL_MS
#define TIMER_INTERVAL_MS        1000

#if USING_TIMER_TC3
  #define SELECTED_TIMER      TIMER_TC3
#elif USING_TIMER_TC4
  #define SELECTED_TIMER      TIMER_TC4
#elif USING_TIMER_TC5
  #define SELECTED_TIMER      TIMER_TC5
#elif USING_TIMER_TCC
  #define SELECTED_TIMER      TIMER_TCC
#elif USING_TIMER_TCC1
  #define SELECTED_TIMER      TIMER_TCC1
#elif USING_TIMER_TCC2
  #define SELECTED_TIMER      TIMER_TCC
#else
  #error You have to select 1 Timer  
#endif

// Init selected SAMD timer
SAMDTimer ITimer(SELECTED_TIMER);

// Init SAMD_ISR_Timer
// Each SAMD_ISR_Timer can service 16 different ISR-based timers
ISR_Timer SAMD_ISR_Timer;

2.2 Set Hardware Timer Interval and attach Timer Interrupt Handler functions

void TimerHandler(void)
{
  ISR_Timer.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 SAMD, 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
}
  
void doingSomething5s()
{
  // Doing something here inside ISR
}

void doingSomething11s()
{
  // Doing something here inside ISR
}

void doingSomething101s()
{
  // Doing something here inside ISR
}

void setup()
{
  ....
  
  // Interval in microsecs
  if (ITimer.attachInterruptInterval_MS(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
  SAMD_ISR_Timer.setInterval(TIMER_INTERVAL_2S, doingSomething2s);
  SAMD_ISR_Timer.setInterval(TIMER_INTERVAL_5S, doingSomething5s);
  SAMD_ISR_Timer.setInterval(TIMER_INTERVAL_11S, doingSomething11s);
  SAMD_ISR_Timer.setInterval(TIMER_INTERVAL_101S, doingSomething101s);
}

Examples:

Example ISR_16_Timers_Array_Complex

SAMD_TimerInterrupt/examples/ISR_16_Timers_Array_Complex/ISR_16_Timers_Array_Complex.ino

Lines 35 to 418 in 89522e1

    
           #if !( defined(ARDUINO_SAMD_ZERO) || defined(ARDUINO_SAMD_MKR1000) || defined(ARDUINO_SAMD_MKRWIFI1010) \ 
        
                 || defined(ARDUINO_SAMD_NANO_33_IOT) || defined(ARDUINO_SAMD_MKRFox1200) || defined(ARDUINO_SAMD_MKRWAN1300) || defined(ARDUINO_SAMD_MKRWAN1310) \ 
        
                 || defined(ARDUINO_SAMD_MKRGSM1400) || defined(ARDUINO_SAMD_MKRNB1500) || defined(ARDUINO_SAMD_MKRVIDOR4000) \ 
        
                 || defined(ARDUINO_SAMD_CIRCUITPLAYGROUND_EXPRESS) || defined(__SAMD51__) || defined(__SAMD51J20A__) \ 
        
                 || defined(__SAMD51J19A__) || defined(__SAMD51G19A__) || defined(__SAMD51P19A__)  \ 
        
                 || defined(__SAMD21E15A__) || defined(__SAMD21E16A__) || defined(__SAMD21E17A__) || defined(__SAMD21E18A__) \ 
        
                 || defined(__SAMD21G15A__) || defined(__SAMD21G16A__) || defined(__SAMD21G17A__) || defined(__SAMD21G18A__) \ 
        
                 || defined(__SAMD21J15A__) || defined(__SAMD21J16A__) || defined(__SAMD21J17A__) || defined(__SAMD21J18A__) ) 
        
             #error This code is designed to run on SAMD21/SAMD51 platform! Please check your Tools->Board setting. 
        
           #endif 
        
           ///////////////////////////////////////////////////////////////// 
        
           // These define's must be placed at the beginning before #include "SAMDTimerInterrupt.h" 
        
           // _TIMERINTERRUPT_LOGLEVEL_ from 0 to 4 
        
           // Don't define _TIMERINTERRUPT_LOGLEVEL_ > 0. Only for special ISR debugging only. Can hang the system. 
        
           // Don't define TIMER_INTERRUPT_DEBUG > 2. Only for special ISR debugging only. Can hang the system. 
        
           #define TIMER_INTERRUPT_DEBUG         0 
        
           #define _TIMERINTERRUPT_LOGLEVEL_     0 
        
           // Select only one to be true for SAMD21. Must must be placed at the beginning before #include "SAMDTimerInterrupt.h" 
        
           #define USING_TIMER_TC3         true      // Only TC3 can be used for SAMD51 
        
           #define USING_TIMER_TC4         false     // Not to use with Servo library 
        
           #define USING_TIMER_TC5         false 
        
           #define USING_TIMER_TCC         false 
        
           #define USING_TIMER_TCC1        false 
        
           #define USING_TIMER_TCC2        false     // Don't use this, can crash on some boards 
        
           // Uncomment To test if conflict with Servo library 
        
           //#include "Servo.h" 
        
           ///////////////////////////////////////////////////////////////// 
        
           // To be included only in main(), .ino with setup() to avoid `Multiple Definitions` Linker Error 
        
           #include "SAMDTimerInterrupt.h" 
        
           // To be included only in main(), .ino with setup() to avoid `Multiple Definitions` Linker Error 
        
           #include "SAMD_ISR_Timer.h" 
        
           #include <SimpleTimer.h>              // https://github.com/jfturcot/SimpleTimer 
        
           #ifndef LED_BUILTIN 
        
           #define LED_BUILTIN       13 
        
           #endif 
        
           #ifndef LED_BLUE 
        
           #define LED_BLUE          2 
        
           #endif 
        
           #ifndef LED_RED 
        
           #define LED_RED           3 
        
           #endif 
        
           // TC3, TC4, TC5 max permissible HW_TIMER_INTERVAL_US is 1398101 us, larger will overflow, therefore not permitted 
        
           // Use TCC, TCC1, TCC2 for longer HW_TIMER_INTERVAL_US 
        
           #define HW_TIMER_INTERVAL_US      10000L 
        
           volatile uint32_t startMillis = 0; 
        
           /////////////////////////////////////////////// 
        
           #if (TIMER_INTERRUPT_USING_SAMD21) 
        
             #if USING_TIMER_TC3 
        
               #define SELECTED_TIMER      TIMER_TC3 
        
             #elif USING_TIMER_TC4 
        
               #define SELECTED_TIMER      TIMER_TC4 
        
             #elif USING_TIMER_TC5 
        
               #define SELECTED_TIMER      TIMER_TC5 
        
             #elif USING_TIMER_TCC 
        
               #define SELECTED_TIMER      TIMER_TCC 
        
             #elif USING_TIMER_TCC1 
        
               #define SELECTED_TIMER      TIMER_TCC1 
        
             #elif USING_TIMER_TCC2 
        
               #define SELECTED_TIMER      TIMER_TCC 
        
             #else 
        
               #error You have to select 1 Timer   
        
             #endif 
        
           #else 
        
             #if !(USING_TIMER_TC3) 
        
               #error You must select TC3 for SAMD51 
        
             #endif 
        
             #define SELECTED_TIMER      TIMER_TC3 
        
           #endif   
        
           // Init selected SAMD timer 
        
           SAMDTimer ITimer(SELECTED_TIMER); 
        
           //////////////////////////////////////////////// 
        
           // Init SAMD_ISR_Timer 
        
           // Each SAMD_ISR_Timer can service 16 different ISR-based timers 
        
           SAMD_ISR_Timer ISR_Timer; 
        
           #define LED_TOGGLE_INTERVAL_MS        2000L 
        
           void TimerHandler() 
        
           { 
        
             static bool toggle  = false; 
        
             static int timeRun  = 0; 
        
             ISR_Timer.run(); 
        
             // Toggle LED every LED_TOGGLE_INTERVAL_MS = 2000ms = 2s 
        
             if (++timeRun == ((LED_TOGGLE_INTERVAL_MS * 1000) / HW_TIMER_INTERVAL_US) ) 
        
             { 
        
               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; 
        
           // 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 && millis() < 5000); 
        
             delay(100); 
        
             Serial.print(F("\nStarting ISR_16_Timers_Array_Complex on ")); Serial.println(BOARD_NAME); 
        
             Serial.println(SAMD_TIMER_INTERRUPT_VERSION); 
        
             Serial.print(F("CPU Frequency = ")); Serial.print(F_CPU / 1000000); Serial.println(F(" MHz")); 
        
             // Interval in microsecs 
        
             if (ITimer.attachInterruptInterval(HW_TIMER_INTERVAL_US, TimerHandler)) 
        
             { 
        
               startMillis = millis(); 
        
               Serial.print(F("Starting ITimer OK, millis() = ")); Serial.println(startMillis); 
        
             } 
        
             else 
        
               Serial.println(F("Can't set ITimer. Select another freq. or timer")); 
        
             startMillis = millis(); 
        
             // 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_Timer.setInterval(curISRTimerData[i].TimerInterval, curISRTimerData[i].irqCallbackFunc); 
        
           #else 
        
               previousMillis[i] = millis(); 
        
               ISR_Timer.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_Timer_Complex_WiFiNINA on Arduino SAMD21 SAMD_NANO_33_IOT using WiFiNINA

The following is the sample terminal output when running example ISR_Timer_Complex_WiFiNINA on SAMD_NANO_33_IOT using Built-in WiFiNINA 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 7.937s !!!. Then in loop(), it's also activated every 3s.

Starting ISR_Timer_Complex_WiFiNINA on SAMD_NANO_33_IOT
SAMDTimerInterrupt v1.10.1
CPU Frequency = 48 MHz
[TISR] SAMDTimerInterrupt: F_CPU (MHz) = 48 , TIMER_HZ = 48
[TISR] TC_Timer::startTimer _Timer = 0x 42002c00 , TC3 = 0x 42002c00
Starting  ITimer OK, millis() = 810
Start Blynk
[1571] WiFiNINA Firmware Version: 1.4.1
[1572] Con2:HueNet1
2s: Delta ms = 2000
[5439] ConW OK
[5439] IP:192.168.2.98
[5439] 
    ___  __          __
   / _ )/ /_ _____  / /__
  / _  / / // / _ \/  '_/
 /____/_/\_, /_//_/_/\_\
        /___/ v0.6.1 on NANO_33_IOT

[5440] BlynkArduinoClient.connect: Connecting to account.duckdns.org:8080
[5673] Ready (ping: 6ms).
IP = 192.168.2.98
2s: Delta ms = 2000
blynkDoingSomething2s: Delta programmed ms = 2000, actual = 7937
2s: Delta ms = 2000
2s: Delta ms = 2000
5s: Delta ms = 5000
blynkDoingSomething2s: Delta programmed ms = 2000, actual = 3002
2s: Delta ms = 2000
blynkDoingSomething2s: Delta programmed ms = 2000, actual = 3002
2s: Delta ms = 2000
5s: Delta ms = 5000
2s: Delta ms = 2000
blynkDoingSomething2s: Delta programmed ms = 2000, actual = 3002
2s: Delta ms = 2000
blynkDoingSomething2s: Delta programmed ms = 2000, actual = 3004
2s: Delta ms = 2000
5s: Delta ms = 5000
2s: Delta ms = 2000
11s: Delta ms = 11000
blynkDoingSomething2s: Delta programmed ms = 2000, actual = 3002
2s: Delta ms = 2000
5s: Delta ms = 5000
blynkDoingSomething2s: Delta programmed ms = 2000, actual = 3003
2s: Delta ms = 2000
2s: Delta ms = 2000
blynkDoingSomething2s: Delta programmed ms = 2000, actual = 3002
2s: Delta ms = 2000
5s: Delta ms = 5000
blynkDoingSomething2s: Delta programmed ms = 2000, actual = 3004
2s: Delta ms = 2000
11s: Delta ms = 11000
2s: Delta ms = 2000
blynkDoingSomething2s: Delta programmed ms = 2000, actual = 3002
5s: Delta ms = 5000
2s: Delta ms = 2000

2. TimerInterruptTest on Adafruit SAMD51 ITSYBITSY_M4

The following is the sample terminal output when running example TimerInterruptTest on Adafruit SAMD51 ITSYBITSY_M4 to demonstrate how to start/stop Hardware Timers.

Starting TimerInterruptTest on ITSYBITSY_M4
SAMDTimerInterrupt v1.10.1
CPU Frequency = 48 MHz
[TISR] SAMDTimerInterrupt: F_CPU (MHz) = 120 , TIMER_HZ = 48
[TISR] TC_Timer::startTimer _Timer = 0x 0x4101c000 , TC3 = 0x 0x4101c000
Starting  ITimer1 OK, millis() = 1820
ITimer0: millis() = 2820, delta = 1000
ITimer0: millis() = 3820, delta = 1000
ITimer0: millis() = 4820, delta = 1000
Stop ITimer0, millis() = 5001
Start ITimer0, millis() = 10002
ITimer0: millis() = 11002, delta = 1000
ITimer0: millis() = 12002, delta = 1000
ITimer0: millis() = 13002, delta = 1000
ITimer0: millis() = 14002, delta = 1000
ITimer0: millis() = 15002, delta = 1000
Stop ITimer0, millis() = 15003
Start ITimer0, millis() = 20004
ITimer0: millis() = 21004, delta = 1000
ITimer0: millis() = 22004, delta = 1000
ITimer0: millis() = 23004, delta = 1000
ITimer0: millis() = 24004, delta = 1000
ITimer0: millis() = 25004, delta = 1000
Stop ITimer0, millis() = 25005
Start ITimer0, millis() = 30006
ITimer0: millis() = 31006, delta = 1000
ITimer0: millis() = 32006, delta = 1000
ITimer0: millis() = 33006, delta = 1000
ITimer0: millis() = 34006, delta = 1000
ITimer0: millis() = 35006, delta = 1000
Stop ITimer0, millis() = 35007
Start ITimer0, millis() = 40008
ITimer0: millis() = 41008, delta = 1000
ITimer0: millis() = 42008, delta = 1000
ITimer0: millis() = 43008, delta = 1000
ITimer0: millis() = 44008, delta = 1000
ITimer0: millis() = 45008, delta = 1000
Stop ITimer0, millis() = 45009
Start ITimer0, millis() = 50010
ITimer0: millis() = 51010, delta = 1000
ITimer0: millis() = 52010, delta = 1000
ITimer0: millis() = 53010, delta = 1000
ITimer0: millis() = 54010, delta = 1000
ITimer0: millis() = 55010, delta = 1000
Stop ITimer0, millis() = 55011
Start ITimer0, millis() = 60012
ITimer0: millis() = 61012, delta = 1000
ITimer0: millis() = 62012, delta = 1000
ITimer0: millis() = 63012, delta = 1000
ITimer0: millis() = 64012, delta = 1000
ITimer0: millis() = 65012, delta = 1000
Stop ITimer0, millis() = 65013
Start ITimer0, millis() = 70014
ITimer0: millis() = 71014, delta = 1000
ITimer0: millis() = 72014, delta = 1000
ITimer0: millis() = 73014, delta = 1000
ITimer0: millis() = 74014, delta = 1000
ITimer0: millis() = 75014, delta = 1000
Stop ITimer0, millis() = 75015
Start ITimer0, millis() = 80016
ITimer0: millis() = 81016, delta = 1000
ITimer0: millis() = 82016, delta = 1000
ITimer0: millis() = 83016, delta = 1000
ITimer0: millis() = 84016, delta = 1000
ITimer0: millis() = 85016, delta = 1000
Stop ITimer0, millis() = 85017
Start ITimer0, millis() = 90018
ITimer0: millis() = 91018, delta = 1000

3. Argument_None on Arduino SAMD21 SAMD_NANO_33_IOT

The following is the sample terminal output when running example Argument_None on Arduino SAMD21 SAMD_NANO_33_IOT to demonstrate how to start/stop Multiple Hardware Timers.

Starting Argument_None on SAMD_NANO_33_IOT
SAMDTimerInterrupt v1.10.1
CPU Frequency = 48 MHz
[TISR] SAMDTimerInterrupt: F_CPU (MHz) = 48 , TIMER_HZ = 48
[TISR] TC_Timer::startTimer _Timer = 0x 42002c00 , TC3 = 0x 42002c00
Starting  ITimer1 OK, millis() = 910
F_CPU (MHz) = 48
TC_Timer::startTimer _Timer = 0x42002000, TCC0 = 0x42002000
Starting  ITimer1 OK, millis() = 911
ITimer0: millis() = 1410, delta = 500
ITimer0: millis() = 1910, delta = 500
ITimer0: millis() = 2410, delta = 500
ITimer0: millis() = 2910, delta = 500
ITimer1: millis() = 2911, delta = 2000
ITimer0: millis() = 3410, delta = 500
ITimer0: millis() = 3910, delta = 500
ITimer0: millis() = 4410, delta = 500
ITimer0: millis() = 4910, delta = 500
ITimer1: millis() = 4911, delta = 2000
ITimer0: millis() = 5410, delta = 500
ITimer0: millis() = 5910, delta = 500
ITimer0: millis() = 6410, delta = 500
ITimer0: millis() = 6910, delta = 500
ITimer1: millis() = 6911, delta = 2000
ITimer0: millis() = 7410, delta = 500
ITimer0: millis() = 7910, delta = 500
ITimer0: millis() = 8410, delta = 500
ITimer0: millis() = 8910, delta = 500
ITimer1: millis() = 8911, delta = 2000
ITimer0: millis() = 9410, delta = 500
ITimer0: millis() = 9910, delta = 500
ITimer0: millis() = 10410, delta = 500
ITimer0: millis() = 10910, delta = 500
ITimer1: millis() = 10911, delta = 2000
ITimer0: millis() = 11410, delta = 500
ITimer0: millis() = 11910, delta = 500

4. ISR_16_Timers_Array on Arduino SAMD21 SAMD_NANO_33_IOT

The following is the sample terminal output when running example ISR_16_Timers_Array on Arduino SAMD21 SAMD_NANO_33_IOT to demonstrate the accuracy of ISR Hardware Timer, especially when system is very busy or blocked. The 16 independent ISR timers are programmed to be activated repetitively after certain intervals, is activated exactly after that programmed interval !!!

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

In this example, 16 independent ISR Timers are used, yet utilized just one Hardware Timer. The Timer Intervals and Function Pointers are stored in arrays to facilitate the code modification.

Starting ISR_16_Timers_Array on SAMD_NANO_33_IOT
SAMDTimerInterrupt v1.10.1
CPU Frequency = 48 MHz
[TISR] SAMDTimerInterrupt: F_CPU (MHz) = 48 , TIMER_HZ = 48
[TISR] TC_Timer::startTimer _Timer = 0x 42002c00 , TC3 = 0x 42002c00
Starting  ITimer OK, millis() = 1421
1s: Delta ms = 1000, ms = 2421
1s: Delta ms = 1000, ms = 3421
2s: Delta ms = 2000, ms = 3421
1s: Delta ms = 1000, ms = 4421
3s: Delta ms = 3000, ms = 4421
1s: Delta ms = 1000, ms = 5421
2s: Delta ms = 2000, ms = 5421
4s: Delta ms = 4000, ms = 5421
1s: Delta ms = 1000, ms = 6421
5s: Delta ms = 5000, ms = 6421
1s: Delta ms = 1000, ms = 7421
2s: Delta ms = 2000, ms = 7421
3s: Delta ms = 3000, ms = 7421
6s: Delta ms = 6000, ms = 7421
1s: Delta ms = 1000, ms = 8421
7s: Delta ms = 7000, ms = 8421
1s: Delta ms = 1000, ms = 9421
2s: Delta ms = 2000, ms = 9421
4s: Delta ms = 4000, ms = 9421
8s: Delta ms = 8000, ms = 9421
1s: Delta ms = 1000, ms = 10421
3s: Delta ms = 3000, ms = 10421
9s: Delta ms = 9000, ms = 10421
1s: Delta ms = 1000, ms = 11421
2s: Delta ms = 2000, ms = 11421
5s: Delta ms = 5000, ms = 11421
10s: Delta ms = 10000, ms = 11421
simpleTimerDoingSomething2s: Delta programmed ms = 2000, actual = 10000
1s: Delta ms = 1000, ms = 12421
11s: Delta ms = 11000, ms = 12421
1s: Delta ms = 1000, ms = 13421
2s: Delta ms = 2000, ms = 13421
3s: Delta ms = 3000, ms = 13421
4s: Delta ms = 4000, ms = 13421
6s: Delta ms = 6000, ms = 13421
12s: Delta ms = 12000, ms = 13421
1s: Delta ms = 1000, ms = 14421
13s: Delta ms = 13000, ms = 14421
1s: Delta ms = 1000, ms = 15421
2s: Delta ms = 2000, ms = 15421
7s: Delta ms = 7000, ms = 15421
14s: Delta ms = 14000, ms = 15421
1s: Delta ms = 1000, ms = 16421
3s: Delta ms = 3000, ms = 16421
5s: Delta ms = 5000, ms = 16421
15s: Delta ms = 15000, ms = 16421
1s: Delta ms = 1000, ms = 17421
2s: Delta ms = 2000, ms = 17421
4s: Delta ms = 4000, ms = 17421
8s: Delta ms = 8000, ms = 17421
16s: Delta ms = 16000, ms = 17421
1s: Delta ms = 1000, ms = 18421
1s: Delta ms = 1000, ms = 19421
2s: Delta ms = 2000, ms = 19421
3s: Delta ms = 3000, ms = 19421
6s: Delta ms = 6000, ms = 19421
9s: Delta ms = 9000, ms = 19421
1s: Delta ms = 1000, ms = 20421
1s: Delta ms = 1000, ms = 21421
2s: Delta ms = 2000, ms = 21421
4s: Delta ms = 4000, ms = 21421
5s: Delta ms = 5000, ms = 21421
10s: Delta ms = 10000, ms = 21421
simpleTimerDoingSomething2s: Delta programmed ms = 2000, actual = 10000
1s: Delta ms = 1000, ms = 22421
3s: Delta ms = 3000, ms = 22421
7s: Delta ms = 7000, ms = 22421
1s: Delta ms = 1000, ms = 23421
2s: Delta ms = 2000, ms = 23421
11s: Delta ms = 11000, ms = 23421
1s: Delta ms = 1000, ms = 24421
1s: Delta ms = 1000, ms = 25421
2s: Delta ms = 2000, ms = 25421
3s: Delta ms = 3000, ms = 25421
4s: Delta ms = 4000, ms = 25421
6s: Delta ms = 6000, ms = 25421
8s: Delta ms = 8000, ms = 25421
12s: Delta ms = 12000, ms = 25421
1s: Delta ms = 1000, ms = 26421
5s: Delta ms = 5000, ms = 26421
1s: Delta ms = 1000, ms = 27421
2s: Delta ms = 2000, ms = 27421
13s: Delta ms = 13000, ms = 27421
1s: Delta ms = 1000, ms = 28421
3s: Delta ms = 3000, ms = 28421
9s: Delta ms = 9000, ms = 28421
1s: Delta ms = 1000, ms = 29421
2s: Delta ms = 2000, ms = 29421
4s: Delta ms = 4000, ms = 29421
7s: Delta ms = 7000, ms = 29421
14s: Delta ms = 14000, ms = 29421
1s: Delta ms = 1000, ms = 30421
1s: Delta ms = 1000, ms = 31421
2s: Delta ms = 2000, ms = 31421
3s: Delta ms = 3000, ms = 31421
5s: Delta ms = 5000, ms = 31421
6s: Delta ms = 6000, ms = 31421
10s: Delta ms = 10000, ms = 31421
15s: Delta ms = 15000, ms = 31421
simpleTimerDoingSomething2s: Delta programmed ms = 2000, actual = 10000
1s: Delta ms = 1000, ms = 32421
1s: Delta ms = 1000, ms = 33421
2s: Delta ms = 2000, ms = 33421
4s: Delta ms = 4000, ms = 33421
8s: Delta ms = 8000, ms = 33421
16s: Delta ms = 16000, ms = 33421
1s: Delta ms = 1000, ms = 34421
3s: Delta ms = 3000, ms = 34421
11s: Delta ms = 11000, ms = 34421

5. Change_Interval on Arduino SAMD21 SAMD_NANO_33_IOT

The following is the sample terminal output when running example Change_Interval on Arduino SAMD21 SAMD_NANO_33_IOT to demonstrate how to change Timer Interval on-the-fly

Starting Change_Interval on SAMD_NANO_33_IOT
SAMDTimerInterrupt v1.10.1
CPU Frequency = 48 MHz
[TISR] SAMDTimerInterrupt: F_CPU (MHz) = 48 , TIMER_HZ = 48
[TISR] TC_Timer::startTimer _Timer = 0x 42002c00 , TC3 = 0x 42002c00
Starting  ITimer OK, millis() = 1131
Time = 10001, TimerCount = 17
Time = 20002, TimerCount = 37
[TISR] SAMDTimerInterrupt: F_CPU (MHz) = 48 , TIMER_HZ = 48
[TISR] TC_Timer::startTimer _Timer = 0x 42002c00 , TC3 = 0x 42002c00
Changing Interval, Timer = 1000
Time = 30003, TimerCount = 47
Time = 40004, TimerCount = 57
[TISR] SAMDTimerInterrupt: F_CPU (MHz) = 48 , TIMER_HZ = 48
[TISR] TC_Timer::startTimer _Timer = 0x 42002c00 , TC3 = 0x 42002c00
Changing Interval, Timer = 500
Time = 50005, TimerCount = 77
Time = 60006, TimerCount = 97
[TISR] SAMDTimerInterrupt: F_CPU (MHz) = 48 , TIMER_HZ = 48
[TISR] TC_Timer::startTimer _Timer = 0x 42002c00 , TC3 = 0x 42002c00
Changing Interval, Timer = 1000
Time = 70007, TimerCount = 107
Time = 80008, TimerCount = 117
[TISR] SAMDTimerInterrupt: F_CPU (MHz) = 48 , TIMER_HZ = 48
[TISR] TC_Timer::startTimer _Timer = 0x 42002c00 , TC3 = 0x 42002c00
Changing Interval, Timer = 500
Time = 90009, TimerCount = 137
Time = 100010, TimerCount = 157
[TISR] SAMDTimerInterrupt: F_CPU (MHz) = 48 , TIMER_HZ = 48
[TISR] TC_Timer::startTimer _Timer = 0x 42002c00 , TC3 = 0x 42002c00
Changing Interval, Timer = 1000
Time = 110011, TimerCount = 167
Time = 120012, TimerCount = 177
[TISR] SAMDTimerInterrupt: F_CPU (MHz) = 48 , TIMER_HZ = 48
[TISR] TC_Timer::startTimer _Timer = 0x 42002c00 , TC3 = 0x 42002c00
Changing Interval, Timer = 500
Time = 130013, TimerCount = 197
Time = 140014, TimerCount = 217
[TISR] SAMDTimerInterrupt: F_CPU (MHz) = 48 , TIMER_HZ = 48
[TISR] TC_Timer::startTimer _Timer = 0x 42002c00 , TC3 = 0x 42002c00
Changing Interval, Timer = 1000
Time = 150015, TimerCount = 227
Time = 160016, TimerCount = 237
[TISR] SAMDTimerInterrupt: F_CPU (MHz) = 48 , TIMER_HZ = 48
[TISR] TC_Timer::startTimer _Timer = 0x 42002c00 , TC3 = 0x 42002c00
Changing Interval, Timer = 500
Time = 170017, TimerCount = 257
Time = 180018, TimerCount = 277
[TISR] SAMDTimerInterrupt: F_CPU (MHz) = 48 , TIMER_HZ = 48
[TISR] TC_Timer::startTimer _Timer = 0x 42002c00 , TC3 = 0x 42002c00
Changing Interval, Timer = 1000
Time = 190019, TimerCount = 287
Time = 200020, TimerCount = 297

6. RepeatedAttachInterrupt_uS on SAMD21 SEEED_XIAO_M0

The following is the sample terminal output when running example RepeatedAttachInterrupt_uS on SEEED_XIAO_M0 to demonstrate how to change Timer Interval on-the-fly

Starting RepeatedAttachInterrupt_uS on SEEED_XIAO_M0
SAMDTimerInterrupt v1.10.1
CPU Frequency = 48 MHz
[TISR] _period = 19995 , frequency = 50.01
[TISR] SAMDTimerInterrupt: F_CPU (MHz) = 48 , TIMER_HZ = 48
[TISR] TCC_Timer::startTimer _Timer = 0x 42002000 , TCC0 = 0x 42002000
[TISR] SAMD21 TCC period = 19995 , _prescaler = 16
[TISR] _compareValue = 59984
myClockTimer (19995) = 19993           <========== OK===============================<=======OK
[TISR] _period = 19995 , frequency = 50.01
[TISR] SAMDTimerInterrupt: F_CPU (MHz) = 48 , TIMER_HZ = 48
[TISR] TCC_Timer::startTimer _Timer = 0x 42002000 , TCC0 = 0x 42002000
[TISR] SAMD21 TCC period = 19995 , _prescaler = 16
[TISR] _compareValue = 59984
myClockTimer (19995) = 19993           <========== OK===============================<=======OK
[TISR] _period = 19995 , frequency = 50.01
[TISR] SAMDTimerInterrupt: F_CPU (MHz) = 48 , TIMER_HZ = 48
[TISR] TCC_Timer::startTimer _Timer = 0x 42002000 , TCC0 = 0x 42002000
[TISR] SAMD21 TCC period = 19995 , _prescaler = 16
[TISR] _compareValue = 59984
myClockTimer (19995) = 19993           <========== OK===============================<=======OK
[TISR] _period = 19000 , frequency = 52.63
[TISR] SAMDTimerInterrupt: F_CPU (MHz) = 48 , TIMER_HZ = 48
[TISR] TCC_Timer::startTimer _Timer = 0x 42002000 , TCC0 = 0x 42002000
[TISR] SAMD21 TCC period = 19000 , _prescaler = 16
[TISR] _compareValue = 56999
myClockTimer (19000) = 18998
[TISR] _period = 20005 , frequency = 49.99
[TISR] SAMDTimerInterrupt: F_CPU (MHz) = 48 , TIMER_HZ = 48
[TISR] TCC_Timer::startTimer _Timer = 0x 42002000 , TCC0 = 0x 42002000
[TISR] SAMD21 TCC period = 20005 , _prescaler = 64
[TISR] _compareValue = 15002
myClockTimer (20005) = 20002
[TISR] _period = 30000 , frequency = 33.33
[TISR] SAMDTimerInterrupt: F_CPU (MHz) = 48 , TIMER_HZ = 48
[TISR] TCC_Timer::startTimer _Timer = 0x 42002000 , TCC0 = 0x 42002000
[TISR] SAMD21 TCC period = 30000 , _prescaler = 64
[TISR] _compareValue = 22498
myClockTimer (30000) = 29996
[TISR] _period = 19995 , frequency = 50.01
[TISR] SAMDTimerInterrupt: F_CPU (MHz) = 48 , TIMER_HZ = 48
[TISR] TCC_Timer::startTimer _Timer = 0x 42002000 , TCC0 = 0x 42002000
[TISR] SAMD21 TCC period = 19995 , _prescaler = 16
[TISR] _compareValue = 59984
myClockTimer (19995) = 19993           <========== OK===============================<=======OK
[TISR] _period = 30000 , frequency = 33.33
[TISR] SAMDTimerInterrupt: F_CPU (MHz) = 48 , TIMER_HZ = 48
[TISR] TCC_Timer::startTimer _Timer = 0x 42002000 , TCC0 = 0x 42002000
[TISR] SAMD21 TCC period = 30000 , _prescaler = 64
[TISR] _compareValue = 22498
myClockTimer (30000) = 29997
[TISR] _period = 19995 , frequency = 50.01
[TISR] SAMDTimerInterrupt: F_CPU (MHz) = 48 , TIMER_HZ = 48
[TISR] TCC_Timer::startTimer _Timer = 0x 42002000 , TCC0 = 0x 42002000
[TISR] SAMD21 TCC period = 19995 , _prescaler = 16
[TISR] _compareValue = 59984

7. SAMD21_MultiTimers on SAMD21 SAMD_NANO_33_IOT

The following is the sample terminal output when running example SAMD21_MultiTimers on SAMD_NANO_33_IOT to demonstrate demo the how to use all 6 SAMD21 timers simultaneously.

Starting SAMD21_MultiTimers on SAMD_NANO_33_IOT
SAMDTimerInterrupt v1.10.1
CPU Frequency = 48 MHz
[TISR] _period = 20000.00 , frequency = 50.00
[TISR] _timerNumber = 0
[TISR] SAMDTimerInterrupt: F_CPU (MHz) = 48 , TIMER_HZ = 48
[TISR] TC3_Timer::startTimer _Timer = 0x 42002c00 , TC3 = 0x 42002c00
[TISR] SAMD21 TC3 period = 20000.00 , _prescaler = 16
[TISR] _compareValue = 59999
Starting  TIMER_TC3 OK, millis() = 962
[TISR] _period = 50000.00 , frequency = 20.00
[TISR] _timerNumber = 1
[TISR] SAMDTimerInterrupt: F_CPU (MHz) = 48 , TIMER_HZ = 48
[TISR] TC4_Timer::startTimer _Timer = 0x 42003000 , TC4 = 0x 42003000
[TISR] SAMD21 TC4 period = 50000.00 , _prescaler = 64
[TISR] _compareValue = 37499
Starting  TIMER_TC4 OK, millis() = 964
[TISR] _period = 100000.00 , frequency = 10.00
[TISR] _timerNumber = 2
[TISR] SAMDTimerInterrupt: F_CPU (MHz) = 48 , TIMER_HZ = 48
[TISR] TC5_Timer::startTimer _Timer = 0x 42003400 , TC5 = 0x 42003400
[TISR] SAMD21 TC5 period = 100000.00 , _prescaler = 256
[TISR] _compareValue = 18749
Starting  TIMER_TC5 OK, millis() = 966
[TISR] _period = 200000.00 , frequency = 5.00
[TISR] SAMDTimerInterrupt: F_CPU (MHz) = 48 , TIMER_HZ = 48
[TISR] TCC_Timer::startTimer _Timer = 0x 42002000 , TCC0 = 0x 42002000
[TISR] SAMD21 TCC period = 200000.00 , _prescaler = 256
[TISR] _compareValue = 37499
Starting  TIMER_TCC OK, millis() = 968
[TISR] _period = 500000.00 , frequency = 2.00
[TISR] SAMDTimerInterrupt: F_CPU (MHz) = 48 , TIMER_HZ = 48
[TISR] TCC_Timer::startTimer _Timer = 0x 42002400 , TCC1 = 0x 42002400
[TISR] SAMD21 TCC1 period = 500000.00 , _prescaler = 1024
[TISR] _compareValue = 23436
Starting  TIMER_TCC1 OK, millis() = 970
[TISR] _period = 1000000.00 , frequency = 1.00
[TISR] SAMDTimerInterrupt: F_CPU (MHz) = 48 , TIMER_HZ = 48
[TISR] TCC_Timer::startTimer _Timer = 0x 42002800 , TCC2 = 0x 42002800
[TISR] SAMD21 TCC2 period = 1000000.00 , _prescaler = 1024
[TISR] _compareValue = 46874
========================================
TC3  Actual/Programmed (ms) 20/20
TC4  Actual/Programmed (ms) 50/50
TC5  Actual/Programmed (ms) 100/100
TCC  Actual/Programmed (ms) 200/200
TCC1 Actual/Programmed (ms) 500/500
========================================
TC3  Actual/Programmed (ms) 20/20
TC4  Actual/Programmed (ms) 50/50
TC5  Actual/Programmed (ms) 100/100
TCC  Actual/Programmed (ms) 200/200
TCC1 Actual/Programmed (ms) 500/500

Debug

Debug is enabled by default on Serial.

You can also change the debugging level (TIMERINTERRUPT_LOGLEVEL) from 0 to 4

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

TO DO

Search for bug and improvement.
Similar features for remaining Arduino boards such as SAM-DUE
Add more Timers to SAMD51

DONE

Basic hardware timers for SAMD21 and SAMD51.
More hardware-initiated software-enabled timers
Longer time interval
Similar features for remaining Arduino boards such as ESP32, ESP8266, STM32, nRF52, mbed-nRF52, Teensy, etc.
Add Table of Contents
Fix multiple-definitions linker error
Add support to many more boards, such as SAMD21E1xA, SAMD21G1xA andSAMD21J1xA
Optimize library code by using reference-passing instead of value-passing
Optimize code for setInterval() of SAMD21 TC3
Reverse the change in setInterval() of SAMD21 TC3 to fix bug when using SAMD21 TC3.
Add TC4, TC5, TCC1 and TCC2 Timers to SAMD21
Add example SAMD21_MultiTimers to demo the how to use all 6 SAMD21 timers simultaneously.
Add functions attachInterruptInterval_MS() and setInterval_MS()
Avoid conflict with Servo library. Check Cannot use TimerInterrupt_Generic Library in the same time than Servo Library #11
Prevent overflow of TCx by flagging error
Using float instead of ulong for interval

Contributions and Thanks

Many thanks for everyone for bug reporting, new feature suggesting, testing and contributing to the development of this library.

Use some code from the Tamasa's ZeroTimer Library.
Use some code from the Dennis van Gils' SAMD51_InterruptTimer Library.
Thanks to generationmake to report the issue Doesn't compile with Adafruit Feather M0 #2 leading to new release v1.3.1.
Thanks to thiagothimotti to report the interesting hard-to-find bug in Bug when going from a >20000us period to a <20000us period. The timer period become 4 times greater. #3 leading to new release v1.4.0.
Thanks to generationmake to make a PR in change variable period from unsigned long to float #7 leading to new release v1.5.0.
Thanks to Alexander Golovanov to propose a PR in Add more SAMD21 #10 leading to the support of many new boards in new release v1.6.0
Thanks to Will Powell to report the bug in Multiple Definition Error Not fixed by swapping src_cpp or src_h with src #9 leading to new release v1.6.0.
Thanks to Dave Hooper to report the bug and propose the fix in setInterval on a running timer results in a period significantly longer than the specified period #17 leading to new release v1.7.0
Thanks to Rui Marinheiro to start the discussion in Do I have a brick? I'm unable to upload sketches after using this library! #21 leading to new release v1.8.0 to fix the bug
Thanks to sriccardi-invn to start the discussion in Cannot use TimerInterrupt_Generic Library in the same time than Servo Library #11 leading to new release v1.10.0 to fix the bug and add more features

_{⭐️ Tamasa}	_{Dennis van Gils}	_{generationmake}	_{thiagothimotti}	_{generationmake}	_{Alexander Golovanov}
_{Will Powell}	_{Dave Hooper}	_{Rui Marinheiro}	_{sriccardi-invn}

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

	#if !( defined(ARDUINO_SAMD_ZERO) \|\| defined(ARDUINO_SAMD_MKR1000) \|\| defined(ARDUINO_SAMD_MKRWIFI1010) \
	\|\| defined(ARDUINO_SAMD_NANO_33_IOT) \|\| defined(ARDUINO_SAMD_MKRFox1200) \|\| defined(ARDUINO_SAMD_MKRWAN1300) \|\| defined(ARDUINO_SAMD_MKRWAN1310) \
	\|\| defined(ARDUINO_SAMD_MKRGSM1400) \|\| defined(ARDUINO_SAMD_MKRNB1500) \|\| defined(ARDUINO_SAMD_MKRVIDOR4000) \
	\|\| defined(ARDUINO_SAMD_CIRCUITPLAYGROUND_EXPRESS) \|\| defined(__SAMD51__) \|\| defined(__SAMD51J20A__) \
	\|\| defined(__SAMD51J19A__) \|\| defined(__SAMD51G19A__) \|\| defined(__SAMD51P19A__) \
	\|\| defined(__SAMD21E15A__) \|\| defined(__SAMD21E16A__) \|\| defined(__SAMD21E17A__) \|\| defined(__SAMD21E18A__) \
	\|\| defined(__SAMD21G15A__) \|\| defined(__SAMD21G16A__) \|\| defined(__SAMD21G17A__) \|\| defined(__SAMD21G18A__) \
	\|\| defined(__SAMD21J15A__) \|\| defined(__SAMD21J16A__) \|\| defined(__SAMD21J17A__) \|\| defined(__SAMD21J18A__) )
	#error This code is designed to run on SAMD21/SAMD51 platform! Please check your Tools->Board setting.
	#endif

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

	// These define's must be placed at the beginning before #include "SAMDTimerInterrupt.h"
	// _TIMERINTERRUPT_LOGLEVEL_ from 0 to 4
	// Don't define _TIMERINTERRUPT_LOGLEVEL_ > 0. Only for special ISR debugging only. Can hang the system.
	// Don't define TIMER_INTERRUPT_DEBUG > 2. Only for special ISR debugging only. Can hang the system.
	#define TIMER_INTERRUPT_DEBUG 0
	#define _TIMERINTERRUPT_LOGLEVEL_ 0

	// Select only one to be true for SAMD21. Must must be placed at the beginning before #include "SAMDTimerInterrupt.h"
	#define USING_TIMER_TC3 true // Only TC3 can be used for SAMD51
	#define USING_TIMER_TC4 false // Not to use with Servo library
	#define USING_TIMER_TC5 false
	#define USING_TIMER_TCC false
	#define USING_TIMER_TCC1 false
	#define USING_TIMER_TCC2 false // Don't use this, can crash on some boards

	// Uncomment To test if conflict with Servo library
	//#include "Servo.h"

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

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

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

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

	#ifndef LED_BUILTIN
	#define LED_BUILTIN 13
	#endif

	#ifndef LED_BLUE
	#define LED_BLUE 2
	#endif

	#ifndef LED_RED
	#define LED_RED 3
	#endif

	// TC3, TC4, TC5 max permissible HW_TIMER_INTERVAL_US is 1398101 us, larger will overflow, therefore not permitted
	// Use TCC, TCC1, TCC2 for longer HW_TIMER_INTERVAL_US
	#define HW_TIMER_INTERVAL_US 10000L

	volatile uint32_t startMillis = 0;

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

	#if (TIMER_INTERRUPT_USING_SAMD21)

	#if USING_TIMER_TC3
	#define SELECTED_TIMER TIMER_TC3
	#elif USING_TIMER_TC4
	#define SELECTED_TIMER TIMER_TC4
	#elif USING_TIMER_TC5
	#define SELECTED_TIMER TIMER_TC5
	#elif USING_TIMER_TCC
	#define SELECTED_TIMER TIMER_TCC
	#elif USING_TIMER_TCC1
	#define SELECTED_TIMER TIMER_TCC1
	#elif USING_TIMER_TCC2
	#define SELECTED_TIMER TIMER_TCC
	#else
	#error You have to select 1 Timer
	#endif

	#else

	#if !(USING_TIMER_TC3)
	#error You must select TC3 for SAMD51
	#endif

	#define SELECTED_TIMER TIMER_TC3

	#endif

	// Init selected SAMD timer
	SAMDTimer ITimer(SELECTED_TIMER);

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

	// Init SAMD_ISR_Timer
	// Each SAMD_ISR_Timer can service 16 different ISR-based timers
	SAMD_ISR_Timer ISR_Timer;

	#define LED_TOGGLE_INTERVAL_MS 2000L

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

	ISR_Timer.run();

	// Toggle LED every LED_TOGGLE_INTERVAL_MS = 2000ms = 2s
	if (++timeRun == ((LED_TOGGLE_INTERVAL_MS * 1000) / HW_TIMER_INTERVAL_US) )
	{
	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;

	// 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 && millis() < 5000);

	delay(100);

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

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

	startMillis = millis();

	// 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_Timer.setInterval(curISRTimerData[i].TimerInterval, curISRTimerData[i].irqCallbackFunc);
	#else
	previousMillis[i] = millis();
	ISR_Timer.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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