v1.0.0 for hardware-PWM on ATtiny boards

### Initial Releases v1.0.0

1. Initial coding to support Arduino **AVR ATtiny-based boards (ATtiny3217, etc.)** using [**megaTinyCore**](https://github.com/SpenceKonde/megaTinyCore)

CONTRIBUTING.md

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+## Contributing to ATtiny_PWM
+
+### Reporting Bugs
+
+Please report bugs in ATtiny_PWM if you find them.
+
+However, before reporting a bug please check through the following:
+
+* [Existing Open Issues](https://github.com/khoih-prog/ATtiny_PWM/issues) - someone might have already encountered this.
+
+If you don't find anything, please [open a new issue](https://github.com/khoih-prog/ATtiny_PWM/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 v2.6.3)
+* 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 v2.6.3
+OS: Ubuntu 20.04 LTS
+Board: AVR_CuriosityNano3217
+Linux xy-Inspiron-3593 5.15.0-52-generic #58~20.04.1-Ubuntu SMP Thu Oct 13 13:09:46 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux
+
+Context:
+I encountered a crash while using this library
+
+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_PWM/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!
+
+Please use the `astyle` to reformat the updated library code as follows (demo for Ubuntu Linux)
+
+1. Change directory to the library GitHub
+
+```
+xy@xy-Inspiron-3593:~$ cd Arduino/xy/ATtiny_PWM_GitHub/
+xy@xy-Inspiron-3593:~/Arduino/xy/ATtiny_PWM_GitHub$
+```
+
+2. Issue astyle command
+
+```
+xy@xy-Inspiron-3593:~/Arduino/xy/ATtiny_PWM_GitHub$ bash utils/restyle.sh
+```
+

changelog.md

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+# ATtiny_PWM Library
+
+[![arduino-library-badge](https://www.ardu-badge.com/badge/ATtiny_PWM.svg?)](https://www.ardu-badge.com/ATtiny_PWM)
+[![GitHub release](https://img.shields.io/github/release/khoih-prog/ATtiny_PWM.svg)](https://github.com/khoih-prog/ATtiny_PWM/releases)
+[![GitHub](https://img.shields.io/github/license/mashape/apistatus.svg)](https://github.com/khoih-prog/ATtiny_PWM/blob/master/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_PWM.svg)](http://github.com/khoih-prog/ATtiny_PWM/issues)
+
+---
+---
+
+## Table of Contents
+
+* [Changelog](#changelog)
+  * [Initial Releases v1.0.0](#Initial-Releases-v100)
+
+---
+---
+
+## Changelog
+
+### Initial Releases v1.0.0
+
+1. Initial coding to support Arduino **AVR ATtiny-based boards (ATtiny3217, etc.)** using [**megaTinyCore**](https://github.com/SpenceKonde/megaTinyCore)
+
+
+---
+---
+
+## Copyright
+
+Copyright 2022- Khoi Hoang
+
+

examples/PWM_Basic/PWM_Basic.ino

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+/****************************************************************************************************************************
+  PWM_Basic.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_PWM
+  Licensed under MIT license
+*****************************************************************************************************************************/
+
+#define _PWM_LOGLEVEL_       4
+
+// Select false to use PWM
+#define USING_TIMER       false   //true
+
+#include "ATtiny_PWM.h"
+
+/*
+const uint8_t digital_pin_to_timer[] = {
+  // Left side, top to bottom
+  TIMERA0,         // 0  PA4 WO4 WOA
+  TIMERA0,         // 1  PA5 WO5 WOB
+  #if defined(DAC0)
+  DACOUT,           // 2  PA6
+  #else
+  NOT_ON_TIMER,     // 2  PA6
+  #endif
+  NOT_ON_TIMER,     // 3  PA7
+  NOT_ON_TIMER,     // 4  PB7
+  NOT_ON_TIMER,     // 5  PB6
+  NOT_ON_TIMER,     // 6  PB5 WO2 Alt
+  NOT_ON_TIMER,     // 7  PB4 WO1 Alt
+  NOT_ON_TIMER,     // 8  PB3 WO0 Alt
+  TIMERA0,          // 9  PB2 WO2
+  TIMERA0,          // 10 PB1 WO1
+  // Right side, bottom to top
+  TIMERA0,          // 11 PB0 WO0
+  #if (defined(TCD0) && defined(USE_TIMERD0_PWM))
+  TIMERD0,          // 12 PC0 WOC
+  TIMERD0,          // 13 PC1 WOD
+  #else
+  NOT_ON_TIMER,     // 12 PC0
+  NOT_ON_TIMER,     // 13 PC1
+  #endif
+  NOT_ON_TIMER,     // 14 PC2
+  NOT_ON_TIMER,     // 15 PC3 WO3 Alt
+  NOT_ON_TIMER,     // 16 PC4 WO4 Alt
+  NOT_ON_TIMER,     // 17 PC5 WO5 Alt
+  NOT_ON_TIMER,     // 18 PA1
+  NOT_ON_TIMER,     // 19 PA2
+  TIMERA0,          // 20 PA3 WO3
+  NOT_ON_TIMER      // 21 PA0
+};
+ */
+
+// OK, only PIN_PA4-5:TCA0
+// PIN_PC0-1: TCD0 => not OK yet for frequency
+// Not OK, PIN_PA6, 7, PIN_PB0-2:TCA0
+
+#define pinToUse       PIN_PA5    //PIN_PB4
+
+//creates pwm instance
+ATtiny_PWM* PWM_Instance;
+
+float frequency = 1000.0f;
+
+float dutyCycle = 0.0f;
+
+void setup()
+{
+  Serial.begin(115200);
+
+  while (!Serial && millis() < 5000);
+
+  delay(500);
+
+  Serial.print(F("\nStarting PWM_Basic using PWM on "));
+  Serial.println(BOARD_NAME);
+  Serial.println(AT_TINY_PWM_VERSION);
+
+  //assigns PWM frequency of 1.0 KHz and a duty cycle of 0%
+  PWM_Instance = new ATtiny_PWM(pinToUse, frequency, dutyCycle);
+
+  if ( (!PWM_Instance) || !PWM_Instance->isPWMEnabled())
+  {
+    Serial.print(F("Stop here forever"));
+
+    while (true)
+      delay(10000);
+  }
+}
+
+void loop()
+{
+  // You can change frequency here, anytime
+  frequency = 2000.0f;
+  //frequency = 20.0f;
+  dutyCycle = 20.0f;
+
+  PWM_Instance->setPWM(pinToUse, frequency, dutyCycle);
+  analogWrite(PIN_PA3, dutyCycle * (1 << 8) / 100);
+
+  delay(10000);
+
+  // You can change frequency here, anytime
+  frequency = 5000.0f;
+  //frequency = 50.0f;
+  dutyCycle = 90.0f;
+
+  PWM_Instance->setPWM(pinToUse, frequency, dutyCycle);
+  analogWrite(PIN_PA3, dutyCycle * (1 << 8) / 100);
+
+  //while (1)
+  delay(10000);
+}

examples/PWM_DynamicDutyCycle/PWM_DynamicDutyCycle.ino

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+/****************************************************************************************************************************
+  PWM_DynamicDutyCycle.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_PWM
+  Licensed under MIT license
+*****************************************************************************************************************************/
+
+#define _PWM_LOGLEVEL_       4
+
+// Select false to use PWM
+#define USING_TIMER       false   //true
+
+#include "ATtiny_PWM.h"
+
+/*
+const uint8_t digital_pin_to_timer[] = {
+  // Left side, top to bottom
+  TIMERA0,         // 0  PA4 WO4 WOA
+  TIMERA0,         // 1  PA5 WO5 WOB
+  #if defined(DAC0)
+  DACOUT,           // 2  PA6
+  #else
+  NOT_ON_TIMER,     // 2  PA6
+  #endif
+  NOT_ON_TIMER,     // 3  PA7
+  NOT_ON_TIMER,     // 4  PB7
+  NOT_ON_TIMER,     // 5  PB6
+  NOT_ON_TIMER,     // 6  PB5 WO2 Alt
+  NOT_ON_TIMER,     // 7  PB4 WO1 Alt
+  NOT_ON_TIMER,     // 8  PB3 WO0 Alt
+  TIMERA0,          // 9  PB2 WO2
+  TIMERA0,          // 10 PB1 WO1
+  // Right side, bottom to top
+  TIMERA0,          // 11 PB0 WO0
+  #if (defined(TCD0) && defined(USE_TIMERD0_PWM))
+  TIMERD0,          // 12 PC0 WOC
+  TIMERD0,          // 13 PC1 WOD
+  #else
+  NOT_ON_TIMER,     // 12 PC0
+  NOT_ON_TIMER,     // 13 PC1
+  #endif
+  NOT_ON_TIMER,     // 14 PC2
+  NOT_ON_TIMER,     // 15 PC3 WO3 Alt
+  NOT_ON_TIMER,     // 16 PC4 WO4 Alt
+  NOT_ON_TIMER,     // 17 PC5 WO5 Alt
+  NOT_ON_TIMER,     // 18 PA1
+  NOT_ON_TIMER,     // 19 PA2
+  TIMERA0,          // 20 PA3 WO3
+  NOT_ON_TIMER      // 21 PA0
+};
+ */
+
+// OK, only PIN_PA4-5:TCA0
+// PIN_PC0-1: TCD0 => not OK yet for frequency
+// Not OK, PIN_PA6, 7, PIN_PB0-2:TCA0
+
+#define pinToUse       PIN_PA5    //PIN_PB4
+
+//creates pwm instance
+ATtiny_PWM* PWM_Instance;
+
+float frequency;
+float dutyCycle;
+
+char dashLine[] = "=====================================================================================";
+
+void printPWMInfo(ATtiny_PWM* PWM_Instance)
+{
+  Serial.println(dashLine);
+  Serial.print("Actual data: pin = ");
+  Serial.print(PWM_Instance->getPin());
+  Serial.print(", PWM DC = ");
+  Serial.print(PWM_Instance->getActualDutyCycle());
+  Serial.print(", PWMPeriod = ");
+  Serial.print(PWM_Instance->getPWMPeriod());
+  Serial.print(", PWM Freq (Hz) = ");
+  Serial.println(PWM_Instance->getActualFreq(), 4);
+  Serial.println(dashLine);
+}
+
+void setup()
+{
+  Serial.begin(115200);
+
+  while (!Serial && millis() < 5000);
+
+  delay(500);
+
+  Serial.print(F("\nStarting PWM_DynamicDutyCycle on "));
+  Serial.println(BOARD_NAME);
+  Serial.println(AT_TINY_PWM_VERSION);
+
+  frequency = 5000.0f;
+
+  PWM_Instance = new ATtiny_PWM(pinToUse, frequency, 0.0f);
+
+  if ( (!PWM_Instance) || !PWM_Instance->isPWMEnabled())
+  {
+    Serial.print(F("Stop here forever"));
+
+    while (true)
+      delay(10000);
+  }
+
+  Serial.println(dashLine);
+}
+
+void loop()
+{
+  dutyCycle = 90.0f;
+
+  Serial.print(F("Change PWM DutyCycle to "));
+  Serial.println(dutyCycle);
+  PWM_Instance->setPWM(pinToUse, frequency, dutyCycle);
+
+  printPWMInfo(PWM_Instance);
+
+  delay(5000);
+  dutyCycle = 20.0f;
+
+  Serial.print(F("Change PWM DutyCycle to "));
+  Serial.println(dutyCycle);
+  PWM_Instance->setPWM(pinToUse, frequency, dutyCycle);
+  printPWMInfo(PWM_Instance);
+
+  delay(5000);
+}