v1.0.0 to support AVR ATtiny-based boards

### Initial Release v1.0.0

1. Intial release to support Arduino **AVR ATtiny-based boards (ATtiny3217, etc.) using megaTinyCore**
2. Add notes `howto upload by drag-and-drop` to `CURIOSITY` virtual drive

Author: khoih-prog

CONTRIBUTING.md

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+## Contributing to ATtiny_TimerInterrupt
+
+### Reporting Bugs
+
+Please report bugs in ATtiny_TimerInterrupt library if you find them.
+
+However, before reporting a bug please check through the following:
+
+* [Existing Open Issues](https://github.com/khoih-prog/ATtiny_TimerInterrupt/issues) - someone might have already encountered this.
+
+If you don't find anything, please [open a new issue](https://github.com/khoih-prog/ATtiny_TimerInterrupt/issues/new).
+
+### How to submit a bug report
+
+Please ensure to specify the following:
+
+* Arduino IDE version (e.g. 1.8.19) or Platform.io version
+* `megaTinyCore` Core Version (e.g. megaTinyCore core v2.5.11)
+* Board (e.g. AVR_CuriosityNano3217, etc.)
+* Contextual information (e.g. what you were trying to achieve)
+* Simplest possible steps to reproduce
+* Anything that might be relevant in your opinion, such as:
+  * Operating system (Windows, Ubuntu, etc.) and the output of `uname -a`
+  * Network configuration
+
+
+### Example
+
+```
+Arduino IDE version: 1.8.19
+Arduino megaTinyCore core v2.5.11
+OS: Ubuntu 20.04 LTS
+Board: AVR_CuriosityNano3217
+Linux xy-Inspiron-3593 5.15.0-46-generic #49~20.04.1-Ubuntu SMP Thu Aug 4 19:15:44 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux
+
+Context:
+I encountered a crash while trying to use the Timer Interrupt.
+
+Steps to reproduce:
+1. ...
+2. ...
+3. ...
+4. ...
+```
+### Sending Feature Requests
+
+Feel free to post feature requests. It's helpful if you can explain exactly why the feature would be useful.
+
+There are usually some outstanding feature requests in the [existing issues list](https://github.com/khoih-prog/ATtiny_TimerInterrupt/issues?q=is%3Aopen+is%3Aissue+label%3Aenhancement), feel free to add comments to them.
+
+### Sending Pull Requests
+
+Pull Requests with changes and fixes are also welcome!
+
+

LICENSE

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+MIT License
+
+Copyright (c) 2022 Khoi Hoang
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

changelog.md

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+## ATtiny_TimerInterrupt Library
+
+[![arduino-library-badge](https://www.ardu-badge.com/badge/ATtiny_TimerInterrupt.svg?)](https://www.ardu-badge.com/ATtiny_TimerInterrupt)
+[![GitHub release](https://img.shields.io/github/release/khoih-prog/ATtiny_TimerInterrupt.svg)](https://github.com/khoih-prog/ATtiny_TimerInterrupt/releases)
+[![GitHub](https://img.shields.io/github/license/mashape/apistatus.svg)](https://github.com/khoih-prog/ATtiny_TimerInterrupt/blob/main/LICENSE)
+[![contributions welcome](https://img.shields.io/badge/contributions-welcome-brightgreen.svg?style=flat)](#Contributing)
+[![GitHub issues](https://img.shields.io/github/issues/khoih-prog/ATtiny_TimerInterrupt.svg)](http://github.com/khoih-prog/ATtiny_TimerInterrupt/issues)
+
+## Table of Contents
+
+* [Changelog](#changelog)
+  * [Initial Release v1.0.0](#initial-release-v100)
+
+---
+---
+
+## Changelog
+
+### Initial Release v1.0.0
+
+1. Intial release to support Arduino **AVR ATtiny-based boards (ATtiny3217, etc.) using megaTinyCore**
+2. Add notes `howto upload by drag-and-drop` to `CURIOSITY` virtual drive
+
+

examples/Argument_Complex/Argument_Complex.ino

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+/****************************************************************************************************************************
+  Argument_Complex.ino
+  For Arduino AVR ATtiny-based boards (ATtiny3217, etc.) using megaTinyCore
+  Written by Khoi Hoang
+
+  Built by Khoi Hoang https://github.com/khoih-prog/ATtiny_TimerInterrupt
+  Licensed under MIT license
+
+  Now with we can use these new 16 ISR-based timers, while consuming only 1 hwarware Timer.
+  Their independently-selected, maximum interval is practically unlimited (limited only by unsigned long miliseconds)
+  The accuracy is nearly perfect compared to software timers. The most important feature is they're ISR-based timers
+  Therefore, their executions are not blocked by bad-behaving functions / tasks.
+  This important feature is absolutely necessary for mission-critical tasks.
+*****************************************************************************************************************************/
+
+// Important Note: To use drag-and-drop into CURIOSITY virtual drive if you can program via Arduino IDE
+// For example, check https://ww1.microchip.com/downloads/en/DeviceDoc/40002193A.pdf
+
+#if !( defined(MEGATINYCORE) )
+  #error This is designed only for MEGATINYCORE megaAVR board! Please check your Tools->Board setting
+#endif
+
+// These define's must be placed at the beginning before #include "megaAVR_TimerInterrupt.h"
+// _TIMERINTERRUPT_LOGLEVEL_ from 0 to 4
+// Don't define _TIMERINTERRUPT_LOGLEVEL_ > 0. Only for special ISR debugging only. Can hang the system.
+#define TIMER_INTERRUPT_DEBUG         0
+#define _TIMERINTERRUPT_LOGLEVEL_     0
+
+// Select USING_FULL_CLOCK      == true for  20/16MHz to Timer TCBx => shorter timer, but better accuracy
+// Select USING_HALF_CLOCK      == true for  10/ 8MHz to Timer TCBx => shorter timer, but better accuracy
+// Select USING_250KHZ          == true for 250KHz to Timer TCBx => longer timer,  but worse  accuracy
+// Not select for default 250KHz to Timer TCBx => longer timer,  but worse accuracy
+#define USING_FULL_CLOCK      true
+#define USING_HALF_CLOCK      false
+#define USING_250KHZ          false         // Not supported now
+
+// Try to use RTC, TCA0 or TCD0 for millis()
+#define USE_TIMER_0           false         // Check if used by millis(), Servo or tone()
+#define USE_TIMER_1           true          // Check if used by millis(), Servo or tone()
+
+#if USE_TIMER_0
+  #define CurrentTimer   ITimer0
+#elif USE_TIMER_1
+  #define CurrentTimer   ITimer1
+#else
+  #error You must select one Timer  
+#endif
+
+// To be included only in main(), .ino with setup() to avoid `Multiple Definitions` Linker Error
+#include "ATtiny_TimerInterrupt.h"
+
+#ifdef LED_BUILTIN
+  #undef LED_BUILTIN
+
+  // To modify according to your board
+  // For Curiosity Nano ATtiny3217 => PIN_PA3
+  #if defined(ARDUINO_AVR_CuriosityNano3217) 
+    #define LED_BUILTIN   PIN_PA3
+  #else
+    // standard Arduino pin 13
+    #define LED_BUILTIN   PIN_PA3
+  #endif
+#endif
+
+// standard Serial
+#define SerialDebug       Serial
+
+
+struct pinStruct
+{
+  unsigned int Pin1;
+  unsigned int Pin2;
+  unsigned int Pin3;
+};
+
+volatile pinStruct myOutputPins = { LED_BUILTIN, A0, A1 };
+
+void TimerHandler1(unsigned int outputPinsAddress)
+{
+  static bool toggle = false;
+
+  //timer interrupt toggles pins
+#if (TIMER_INTERRUPT_DEBUG > 1)
+  SerialDebug.print("Toggle pin1 = "); SerialDebug.println( ((pinStruct *) outputPinsAddress)->Pin1 );
+#endif
+  
+  digitalWrite(((pinStruct *) outputPinsAddress)->Pin1, toggle);
+
+#if (TIMER_INTERRUPT_DEBUG > 1)
+  SerialDebug.print("Read pin2 A0 ("); SerialDebug.print(((pinStruct *) outputPinsAddress)->Pin2 );
+  SerialDebug.print(") = ");
+  SerialDebug.println(digitalRead(((pinStruct *) outputPinsAddress)->Pin2) ? "HIGH" : "LOW" );                          
+
+  SerialDebug.print("Read pin3 A1 ("); SerialDebug.print(((pinStruct *) outputPinsAddress)->Pin3 );
+  SerialDebug.print(") = ");
+  SerialDebug.println(digitalRead(((pinStruct *) outputPinsAddress)->Pin3) ? "HIGH" : "LOW" );  
+#endif
+                 
+  toggle = !toggle;
+}
+
+#define TIMER1_INTERVAL_MS    1000
+
+void setup()
+{
+  pinMode(myOutputPins.Pin1, OUTPUT);
+  pinMode(myOutputPins.Pin2, INPUT_PULLUP);
+  pinMode(myOutputPins.Pin3, INPUT_PULLUP);
+    
+  SerialDebug.begin(115200);
+  while (!SerialDebug && millis() < 5000);
+
+  SerialDebug.print(F("\nStarting Argument_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
+
+  // Timer TCB2 is used for micros(), millis(), delay(), etc and can't be used
+  CurrentTimer.init();
+
+  if (CurrentTimer.attachInterruptInterval(TIMER1_INTERVAL_MS, TimerHandler1, (unsigned int) &myOutputPins))
+  {
+    SerialDebug.print(F("Starting ITimer OK, millis() = ")); SerialDebug.println(millis());
+  }
+  else
+    SerialDebug.println(F("Can't set ITimer. Select another freq. or timer"));
+}
+
+void loop()
+{
+}

examples/Argument_None/Argument_None.ino

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+/****************************************************************************************************************************
+  Argument_None.ino
+  For Arduino AVR ATtiny-based boards (ATtiny3217, etc.) using megaTinyCore
+  Written by Khoi Hoang
+
+  Built by Khoi Hoang https://github.com/khoih-prog/ATtiny_TimerInterrupt
+  Licensed under MIT license
+
+  Now with we can use these new 16 ISR-based timers, while consuming only 1 hwarware Timer.
+  Their independently-selected, maximum interval is practically unlimited (limited only by unsigned long miliseconds)
+  The accuracy is nearly perfect compared to software timers. The most important feature is they're ISR-based timers
+  Therefore, their executions are not blocked by bad-behaving functions / tasks.
+  This important feature is absolutely necessary for mission-critical tasks.
+*****************************************************************************************************************************/
+
+// Important Note: To use drag-and-drop into CURIOSITY virtual drive if you can program via Arduino IDE
+// For example, check https://ww1.microchip.com/downloads/en/DeviceDoc/40002193A.pdf
+
+#if !( defined(MEGATINYCORE) )
+  #error This is designed only for MEGATINYCORE megaAVR board! Please check your Tools->Board setting
+#endif
+
+// These define's must be placed at the beginning before #include "megaAVR_TimerInterrupt.h"
+// _TIMERINTERRUPT_LOGLEVEL_ from 0 to 4
+// Don't define _TIMERINTERRUPT_LOGLEVEL_ > 0. Only for special ISR debugging only. Can hang the system.
+#define TIMER_INTERRUPT_DEBUG         0
+#define _TIMERINTERRUPT_LOGLEVEL_     0
+
+// Select USING_FULL_CLOCK      == true for  20/16MHz to Timer TCBx => shorter timer, but better accuracy
+// Select USING_HALF_CLOCK      == true for  10/ 8MHz to Timer TCBx => shorter timer, but better accuracy
+// Select USING_250KHZ          == true for 250KHz to Timer TCBx => longer timer,  but worse  accuracy
+// Not select for default 250KHz to Timer TCBx => longer timer,  but worse accuracy
+#define USING_FULL_CLOCK      true
+#define USING_HALF_CLOCK      false
+#define USING_250KHZ          false         // Not supported now
+
+// Try to use RTC, TCA0 or TCD0 for millis()
+#define USE_TIMER_0           false         // Check if used by millis(), Servo or tone()
+#define USE_TIMER_1           true          // 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"
+
+#define TIMER1_INTERVAL_MS    1000
+
+#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
+
+void TimerHandler1(void)
+{
+  static bool toggle = false;
+
+  //timer interrupt toggles pin LED_BUILTIN
+  digitalWrite(LED_BUILTIN, toggle);
+  toggle = !toggle;
+}
+
+void setup()
+{
+  pinMode(LED_BUILTIN, OUTPUT);
+  
+  SerialDebug.begin(115200);
+  while (!SerialDebug && millis() < 5000);
+
+  SerialDebug.print(F("\nStarting Argument_None on ")); SerialDebug.println(BOARD_NAME);
+  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"));
+}
+
+void loop()
+{
+}