AVR_Slow_PWM Library

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Table of Contents

• Important Change from v1.2.0
• Why do we need this AVR_Slow_PWM library
  • Features
  • Why using ISR-based PWM is better
  • Currently supported Boards
  • Important Notes about ISR
• Changelog
• Prerequisites
• Installation
  • Use Arduino Library Manager
  • Manual Install
  • VS Code & PlatformIO
• HOWTO Fix Multiple Definitions Linker Error
• More useful Information
  • 1. Timer0
  • 2. Timer1
  • 3. Timer2
  • 4. Timer3, Timer4, Timer5
  • 5. Important Notes
• Usage
  • 1. Init Hardware Timer
  • 2. Set PWM Frequency, dutycycle, attach irqCallbackStartFunc and irqCallbackStopFunc functions
• Examples
  • 1. ISR_8_PWMs_Array
  • 2. ISR_8_PWMs_Array_Complex
  • 3. ISR_8_PWMs_Array_Simple
  • 4. ISR_Changing_PWM
  • 5. ISR_Modify_PWM
  • 6. multiFileProject New
• Example ISR_8_PWMs_Array_Complex
• Debug Terminal Output Samples
  • 1. ISR_8_PWMs_Array_Complex on Arduino AVR Leonardo ATMega32U4
  • 2. ISR_8_PWMs_Array on Arduino AVR Mega2560/ADK
  • 3. ISR_8_PWMs_Array_Simple on Arduino AVR Nano
  • 4. ISR_Modify_PWM on Arduino AVR Mega2560/ADK
  • 5. ISR_Changing_PWM on Arduino AVR Mega2560/ADK
• Debug
• Troubleshooting
• Issues
• TO DO
• DONE
• Contributions and Thanks
• Contributing
• License
• Copyright

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Important Change from v1.2.0

Please have a look at HOWTO Fix Multiple Definitions Linker Error

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Why do we need this AVR_Slow_PWM library

Features

This library enables you to use ISR-based PWM channels on AVR-based boards, such as Mega-2560, UNO,Nano, Leonardo, etc., using AVR core to create and output PWM any GPIO pin. Because this library doesn't use the powerful purely hardware-controlled PWM with many limitations, the maximum PWM frequency is currently limited at 500Hz, which is still suitable for many real-life applications. Now you can also modify PWM settings on-the-fly.

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This library enables you to use Interrupt from Hardware Timers on AVR-based boards to create and output PWM to pins. It now supports 16 ISR-based synchronized PWM channels, while consuming only 1 Hardware Timer. PWM interval can be very long (uint64_t microsecs / millisecs). The most important feature is they're ISR-based PWM channels. Therefore, their executions are not blocked by bad-behaving functions or tasks. This important feature is absolutely necessary for mission-critical tasks. These hardware PWM channels, 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 PWM using millis() or micros(). That's necessary if you need to measure some data requiring better accuracy.

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

Now with these new 16 ISR-based PWM-channels, the maximum interval is practically unlimited (limited only by unsigned long milliseconds) while the accuracy is nearly perfect compared to software PWM channels.

The most important feature is they're ISR-based PWM channels. Therefore, their executions are not blocked by bad-behaving functions / tasks. This important feature is absolutely necessary for mission-critical tasks.

The ISR_8_PWMs_Array_Complex example will demonstrate the nearly perfect accuracy, compared to software PWM, by printing the actual period / duty-cycle in microsecs of each of PWM-channels.

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

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

You'll see software-based SimpleTimer 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

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Why using ISR-based PWM 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 PWM channels, 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 PWM channels using millis() or micros(). That's necessary if you need to measure some data requiring better accuracy.

Functions using normal software PWM channels, 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

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Currently supported Boards

1. AVR-based boards using ATMEGA_328P, ATMEGA_2560, ATMEGA_1280, ATMEGA_640, ATMEGA_16U4, ATMEGA_32U4, etc. boards such as Mega-2560, UNO, Nano, Leonardo, etc., using Arduino, Adafruit or Sparkfun AVR core

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Important Notes about ISR

1. Inside the attached function, delay() won’t work and the value returned by millis() will not increment. Serial data received while in the function may be lost. You should declare as volatile any variables that you modify within the attached function.

2. Typically global variables are used to pass data between an ISR and the main program. To make sure variables shared between an ISR and the main program are updated correctly, declare them as volatile.

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Prerequisites

1. Arduino IDE 1.8.19+ for Arduino.

2. Arduino AVR core 1.8.6+ for Arduino AVR boards. Use Arduino Board Manager to install.

3. Adafruit AVR core 1.4.15+ for Adafruit AVR boards. Use Arduino Board Manager to install.

4. Sparkfun AVR core 1.1.13+ for Sparkfun AVR boards. Use Arduino Board Manager to install.

5. To use with certain example

• SimpleTimer library to use with some examples.

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Installation

Use Arduino Library Manager

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

Manual Install

Another way to install is to:

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

VS Code & PlatformIO

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

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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 this .hpp file

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

in many files. But be sure to use the following .h file 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 "AVR_Slow_PWM.h"           //https://github.com/khoih-prog/AVR_Slow_PWM

Check the new multiFileProject example for a HOWTO demo.

Have a look at the discussion in Different behaviour using the src_cpp or src_h lib #80

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More useful Information

From Arduino 101: Timers and Interrupts

1. Timer0:

Timer0 is a 8-bit timer.

In the Arduino world, Timer0 is been used for the timer functions, like delay(), millis() and micros(). If you change Timer0 registers, this may influence the Arduino timer function. So you should know what you are doing.

2. Timer1:

Timer1 is a 16-bit timer. In the Arduino world, the Servo library uses Timer1 on Arduino Uno (Timer5 on Arduino Mega).

3. Timer2:

Timer2 is a 8-bit timer like Timer0. This Timer2 is not available for ATMEGA_16U4, ATMEGA_32U4 boards, such as Leonardo, YUN, ESPLORA, etc. In the Arduino world, the tone() function uses Timer2.

4. Timer3, Timer4, Timer5:

Timer4 is only available on Arduino ATMEGA_2560, ATMEGA_1280, ATMEGA_640, ATMEGA_16U4, ATMEGA_32U4 boards. This Timer4 is 16-bit timer on ATMEGA_2560, ATMEGA_1280, ATMEGA_640 boards and 10-bit (but used as 8-bit in this library) Timer on ATMEGA_16U4, ATMEGA_32U4 boards

Timer3 and Timer5 are only available on Arduino Mega boards. These 2 timers are all 16-bit timers.

5. Important Notes

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

Timer1,3,4 are supported for ATMEGA_16U4, ATMEGA_32U4 boards, such as Leonardo, YUN, ESPLORA, etc.

Only Timer1 and Timer2 are supported for Nano, UNO, etc. boards possessing 3 timers.

Timer1-Timer5 are available for Arduino Mega boards.

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Usage

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

1. Init Hardware Timer

// Select the timers you're using, here ITimer1
#define USE_TIMER_1     true
#define USE_TIMER_2     false
#define USE_TIMER_3     false
#define USE_TIMER_4     false
#define USE_TIMER_5     false

// Init AVR_Slow_PWM, each can service 16 different ISR-based PWM channels
AVR_Slow_PWM ISR_PWM;

2. Set PWM Frequency, dutycycle, attach irqCallbackStartFunc and irqCallbackStopFunc functions

void irqCallbackStartFunc()
{

}

void irqCallbackStopFunc()
{

}

void setup()
{
  ....
  
  // You can use this with PWM_Freq in Hz
  ISR_PWM.setPWM(PWM_Pin, PWM_Freq, PWM_DutyCycle, irqCallbackStartFunc, irqCallbackStopFunc);
                   
  ....                 
}  

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Examples:

1. ISR_8_PWMs_Array
2. ISR_8_PWMs_Array_Complex
3. ISR_8_PWMs_Array_Simple
4. ISR_Changing_PWM
5. ISR_Modify_PWM
6. multiFileProject New

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Example ISR_8_PWMs_Array_Complex

AVR_Slow_PWM/examples/ISR_8_PWMs_Array_Complex/ISR_8_PWMs_Array_Complex.ino

Lines 22 to 508 in e52cd46

	#if ( defined(__AVR_ATmega644__) || defined(__AVR_ATmega644A__) || defined(__AVR_ATmega644P__) || defined(__AVR_ATmega644PA__) || \
	defined(ARDUINO_AVR_UNO) || defined(ARDUINO_AVR_NANO) || defined(ARDUINO_AVR_MINI) || defined(ARDUINO_AVR_ETHERNET) || \
	defined(ARDUINO_AVR_FIO) || defined(ARDUINO_AVR_BT) || defined(ARDUINO_AVR_LILYPAD) || defined(ARDUINO_AVR_PRO) || \
	defined(ARDUINO_AVR_NG) || defined(ARDUINO_AVR_UNO_WIFI_DEV_ED) || defined(ARDUINO_AVR_DUEMILANOVE) || defined(ARDUINO_AVR_FEATHER328P) || \
	defined(ARDUINO_AVR_METRO) || defined(ARDUINO_AVR_PROTRINKET5) || defined(ARDUINO_AVR_PROTRINKET3) || defined(ARDUINO_AVR_PROTRINKET5FTDI) || \
	defined(ARDUINO_AVR_PROTRINKET3FTDI) )
	#define USE_TIMER_1 true
	#else
	#define USE_TIMER_3 true
	#endif
	// These define's must be placed at the beginning before #include "AVR_Slow_PWM.h"
	// _PWM_LOGLEVEL_ from 0 to 4
	// Don't define _PWM_LOGLEVEL_ > 0. Only for special ISR debugging only. Can hang the system.
	#define _PWM_LOGLEVEL_ 3
	#if (_PWM_LOGLEVEL_ > 3)
	#if USE_TIMER_1
	#warning Using Timer1
	#elif USE_TIMER_1
	#warning Using Timer3
	#endif
	#endif
	#define USING_MICROS_RESOLUTION true //false
	// Default is true, uncomment to false
	//#define CHANGING_PWM_END_OF_CYCLE false
	// To be included only in main(), .ino with setup() to avoid `Multiple Definitions` Linker Error
	#include "AVR_Slow_PWM.h"
	#include <SimpleTimer.h> // https://github.com/jfturcot/SimpleTimer
	#define LED_OFF HIGH
	#define LED_ON LOW
	#ifndef LED_BUILTIN
	#define LED_BUILTIN 13
	#endif
	#ifndef LED_BLUE
	#define LED_BLUE 10
	#endif
	#ifndef LED_RED
	#define LED_RED 11
	#endif
	#define USING_HW_TIMER_INTERVAL_MS false //true
	// Don't change these numbers to make higher Timer freq. System can hang
	#define HW_TIMER_INTERVAL_MS 0.1f
	#define HW_TIMER_INTERVAL_FREQ 10000L
	volatile uint32_t startMicros = 0;
	// Init AVR_Slow_PWM, each can service 16 different ISR-based PWM channels
	AVR_Slow_PWM ISR_PWM;
	//////////////////////////////////////////////////////
	void TimerHandler()
	{
	ISR_PWM.run();
	}
	/////////////////////////////////////////////////
	#define PIN_D0 0
	#define PIN_D1 1
	#define PIN_D2 2
	#define PIN_D3 3
	#define PIN_D4 4
	#define PIN_D5 5
	#define PIN_D6 6
	// You can assign pins here. Be careful to select good pin to use or crash, e.g pin 6-11
	uint32_t PWM_Pin[] =
	{
	LED_BUILTIN, PIN_D0, PIN_D1, PIN_D2, PIN_D3, PIN_D4, PIN_D5, PIN_D6
	};
	#define NUMBER_ISR_PWMS ( sizeof(PWM_Pin) / sizeof(uint32_t) )
	typedef void (*irqCallback) ();
	//////////////////////////////////////////////////////
	#define USE_COMPLEX_STRUCT true
	//////////////////////////////////////////////////////
	#if USE_COMPLEX_STRUCT
	typedef struct
	{
	uint32_t PWM_Pin;
	irqCallback irqCallbackStartFunc;
	irqCallback irqCallbackStopFunc;
	float PWM_Freq;
	float PWM_DutyCycle;
	uint32_t deltaMicrosStart;
	uint32_t previousMicrosStart;
	uint32_t deltaMicrosStop;
	uint32_t previousMicrosStop;
	} ISR_PWM_Data;
	// 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 doingSomethingStart(int index);
	void doingSomethingStop(int index);
	#else // #if USE_COMPLEX_STRUCT
	volatile unsigned long deltaMicrosStart [] = { 0, 0, 0, 0, 0, 0, 0, 0 };
	volatile unsigned long previousMicrosStart [] = { 0, 0, 0, 0, 0, 0, 0, 0 };
	volatile unsigned long deltaMicrosStop [] = { 0, 0, 0, 0, 0, 0, 0, 0 };
	volatile unsigned long previousMicrosStop [] = { 0, 0, 0, 0, 0, 0, 0, 0 };
	// You can assign any interval for any timer here, in Microseconds
	uint32_t PWM_Period[] =
	{
	1000, 500, 333, 250, 200, 167, 143, 125
	};
	// You can assign any interval for any timer here, in Hz
	float PWM_Freq[] =
	{
	1.0f, 2.0f, 3.0f, 4.0f, 5.0f, 6.0f, 7.0f, 8.0f,
	};
	// You can assign any interval for any timer here, in Microseconds
	float PWM_DutyCycle[] =
	{
	5.0, 10.0, 20.0, 25.0, 30.0, 35.0, 40.0, 45.0
	};
	void doingSomethingStart(int index)
	{
	unsigned long currentMicros = micros();
	deltaMicrosStart[index] = currentMicros - previousMicrosStart[index];
	previousMicrosStart[index] = currentMicros;
	}
	void doingSomethingStop(int index)
	{
	unsigned long currentMicros = micros();
	// Count from start to stop PWM pulse
	deltaMicrosStop[index] = currentMicros - previousMicrosStart[index];
	previousMicrosStop[index] = currentMicros;
	}
	#endif // #if USE_COMPLEX_STRUCT
	////////////////////////////////////
	// Shared
	////////////////////////////////////
	void doingSomethingStart0()
	{
	doingSomethingStart(0);
	}
	void doingSomethingStart1()
	{
	doingSomethingStart(1);
	}
	void doingSomethingStart2()
	{
	doingSomethingStart(2);
	}
	void doingSomethingStart3()
	{
	doingSomethingStart(3);
	}
	void doingSomethingStart4()
	{
	doingSomethingStart(4);
	}
	void doingSomethingStart5()
	{
	doingSomethingStart(5);
	}
	void doingSomethingStart6()
	{
	doingSomethingStart(6);
	}
	void doingSomethingStart7()
	{
	doingSomethingStart(7);
	}
	//////////////////////////////////////////////////////
	void doingSomethingStop0()
	{
	doingSomethingStop(0);
	}
	void doingSomethingStop1()
	{
	doingSomethingStop(1);
	}
	void doingSomethingStop2()
	{
	doingSomethingStop(2);
	}
	void doingSomethingStop3()
	{
	doingSomethingStop(3);
	}
	void doingSomethingStop4()
	{
	doingSomethingStop(4);
	}
	void doingSomethingStop5()
	{
	doingSomethingStop(5);
	}
	void doingSomethingStop6()
	{
	doingSomethingStop(6);
	}
	void doingSomethingStop7()
	{
	doingSomethingStop(7);
	}
	//////////////////////////////////////////////////////
	#if USE_COMPLEX_STRUCT
	ISR_PWM_Data curISR_PWM_Data[] =
	{
	// pin, irqCallbackStartFunc, irqCallbackStopFunc, PWM_Freq, PWM_DutyCycle, deltaMicrosStart, previousMicrosStart, deltaMicrosStop, previousMicrosStop
	{ LED_BUILTIN, doingSomethingStart0, doingSomethingStop0, 1.0, 5.0, 0, 0, 0, 0 },
	{ PIN_D0, doingSomethingStart1, doingSomethingStop1, 2.0, 10.0, 0, 0, 0, 0 },
	{ PIN_D1, doingSomethingStart2, doingSomethingStop2, 3.0, 20.0, 0, 0, 0, 0 },
	{ PIN_D2, doingSomethingStart3, doingSomethingStop3, 4.0, 25.0, 0, 0, 0, 0 },
	{ PIN_D3, doingSomethingStart4, doingSomethingStop4, 5.0, 30.0, 0, 0, 0, 0 },
	{ PIN_D4, doingSomethingStart5, doingSomethingStop5, 6.0, 35.0, 0, 0, 0, 0 },
	{ PIN_D5, doingSomethingStart6, doingSomethingStop6, 7.0, 40.0, 0, 0, 0, 0 },
	{ PIN_D6, doingSomethingStart7, doingSomethingStop7, 8.0, 45.0, 0, 0, 0, 0 },
	};
	void doingSomethingStart(int index)
	{
	unsigned long currentMicros = micros();
	curISR_PWM_Data[index].deltaMicrosStart = currentMicros - curISR_PWM_Data[index].previousMicrosStart;
	curISR_PWM_Data[index].previousMicrosStart = currentMicros;
	}
	void doingSomethingStop(int index)
	{
	unsigned long currentMicros = micros();
	//curISR_PWM_Data[index].deltaMicrosStop = currentMicros - curISR_PWM_Data[index].previousMicrosStop;
	// Count from start to stop PWM pulse
	curISR_PWM_Data[index].deltaMicrosStop = currentMicros - curISR_PWM_Data[index].previousMicrosStart;
	curISR_PWM_Data[index].previousMicrosStop = currentMicros;
	}
	#else // #if USE_COMPLEX_STRUCT
	irqCallback irqCallbackStartFunc[] =
	{
	doingSomethingStart0, doingSomethingStart1, doingSomethingStart2, doingSomethingStart3,
	doingSomethingStart4, doingSomethingStart5, doingSomethingStart6, doingSomethingStart7
	};
	irqCallback irqCallbackStopFunc[] =
	{
	doingSomethingStop0, doingSomethingStop1, doingSomethingStop2, doingSomethingStop3,
	doingSomethingStop4, doingSomethingStop5, doingSomethingStop6, doingSomethingStop7
	};
	#endif // #if USE_COMPLEX_STRUCT
	//////////////////////////////////////////////////////
	#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 previousMicrosStart = startMicros;
	unsigned long currMicros = micros();
	Serial.print(F("SimpleTimer (us): ")); Serial.print(SIMPLE_TIMER_MS);
	Serial.print(F(", us : ")); Serial.print(currMicros);
	Serial.print(F(", Dus : ")); Serial.println(currMicros - previousMicrosStart);
	for (uint16_t i = 0; i < NUMBER_ISR_PWMS; i++)
	{
	#if USE_COMPLEX_STRUCT
	Serial.print(F("PWM Channel : ")); Serial.print(i);
	Serial.print(F(", prog Period (ms): "));
	Serial.print(1000.0f / curISR_PWM_Data[i].PWM_Freq);
	Serial.print(F(", actual (uS) : ")); Serial.print(curISR_PWM_Data[i].deltaMicrosStart);
	Serial.print(F(", prog DutyCycle : "));
	Serial.print(curISR_PWM_Data[i].PWM_DutyCycle);
	Serial.print(F(", actual : ")); Serial.println((float) curISR_PWM_Data[i].deltaMicrosStop * 100.0f / curISR_PWM_Data[i].deltaMicrosStart);
	//Serial.print(F(", actual deltaMicrosStop : ")); Serial.println(curISR_PWM_Data[i].deltaMicrosStop);
	//Serial.print(F(", actual deltaMicrosStart : ")); Serial.println(curISR_PWM_Data[i].deltaMicrosStart);
	#else
	Serial.print(F("PWM Channel : ")); Serial.print(i);
	Serial.print(1000.0f / PWM_Freq[i]);
	Serial.print(F(", prog. Period (us): ")); Serial.print(PWM_Period[i]);
	Serial.print(F(", actual : ")); Serial.print(deltaMicrosStart[i]);
	Serial.print(F(", prog DutyCycle : "));
	Serial.print(PWM_DutyCycle[i]);
	Serial.print(F(", actual : ")); Serial.println( (float) deltaMicrosStop[i] * 100.0f / deltaMicrosStart[i]);
	//Serial.print(F(", actual deltaMicrosStop : ")); Serial.println(deltaMicrosStop[i]);
	//Serial.print(F(", actual deltaMicrosStart : ")); Serial.println(deltaMicrosStart[i]);
	#endif
	}
	previousMicrosStart = currMicros;
	}
	void setup()
	{
	Serial.begin(115200);
	while (!Serial);
	delay(2000);
	Serial.print(F("\nStarting ISR_8_PWMs_Array_Complex on ")); Serial.println(BOARD_NAME);
	Serial.println(AVR_SLOW_PWM_VERSION);
	Serial.print(F("CPU Frequency = ")); Serial.print(F_CPU / 1000000); Serial.println(F(" MHz"));
	// Timer0 is used for micros(), micros(), delay(), etc and can't be used
	// Select Timer 1-2 for UNO, 1-5 for MEGA, 1,3,4 for 16u4/32u4
	// Timer 2 is 8-bit timer, only for higher frequency
	// Timer 4 of 16u4 and 32u4 is 8/10-bit timer, only for higher frequency
	#if USING_HW_TIMER_INTERVAL_MS
	#if USE_TIMER_1
	ITimer1.init();
	// Using ATmega328 used in UNO => 16MHz CPU clock ,
	if (ITimer1.attachInterruptInterval(HW_TIMER_INTERVAL_MS, TimerHandler))
	{
	Serial.print(F("Starting ITimer1 OK, micros() = ")); Serial.println(micros());
	}
	else
	Serial.println(F("Can't set ITimer1. Select another freq. or timer"));
	#elif USE_TIMER_3
	ITimer3.init();
	if (ITimer3.attachInterruptInterval(HW_TIMER_INTERVAL_MS, TimerHandler))
	{
	Serial.print(F("Starting ITimer3 OK, micros() = ")); Serial.println(micros());
	}
	else
	Serial.println(F("Can't set ITimer3. Select another freq. or timer"));
	#endif
	#else
	#if USE_TIMER_1
	ITimer1.init();
	// Using ATmega328 used in UNO => 16MHz CPU clock ,
	if (ITimer1.attachInterrupt(HW_TIMER_INTERVAL_FREQ, TimerHandler))
	{
	Serial.print(F("Starting ITimer1 OK, micros() = ")); Serial.println(micros());
	}
	else
	Serial.println(F("Can't set ITimer1. Select another freq. or timer"));
	#elif USE_TIMER_3
	ITimer3.init();
	if (ITimer3.attachInterrupt(HW_TIMER_INTERVAL_FREQ, TimerHandler))
	{
	Serial.print(F("Starting ITimer3 OK, micros() = ")); Serial.println(micros());
	}
	else
	Serial.println(F("Can't set ITimer3. Select another freq. or timer"));
	#endif
	#endif
	startMicros = micros();
	// Just to demonstrate, don't use too many ISR Timers if not absolutely necessary
	// You can use up to 16 timer for each ISR_PWM
	for (uint16_t i = 0; i < NUMBER_ISR_PWMS; i++)
	{
	#if USE_COMPLEX_STRUCT
	curISR_PWM_Data[i].previousMicrosStart = startMicros;
	//ISR_PWM.setInterval(curISR_PWM_Data[i].PWM_Period, curISR_PWM_Data[i].irqCallbackStartFunc);
	//void setPWM(uint32_t pin, float frequency, float dutycycle
	// , timer_callback_p StartCallback = nullptr, timer_callback_p StopCallback = nullptr)
	// You can use this with PWM_Freq in Hz
	ISR_PWM.setPWM(curISR_PWM_Data[i].PWM_Pin, curISR_PWM_Data[i].PWM_Freq, curISR_PWM_Data[i].PWM_DutyCycle,
	curISR_PWM_Data[i].irqCallbackStartFunc, curISR_PWM_Data[i].irqCallbackStopFunc);
	#else
	previousMicrosStart[i] = micros();
	// You can use this with PWM_Freq in Hz
	ISR_PWM.setPWM(PWM_Pin[i], PWM_Freq[i], PWM_DutyCycle[i], irqCallbackStartFunc[i], irqCallbackStopFunc[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_PWM 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_PWM 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_PWM.run() here in the loop(). It's already handled by ISR timer.
	simpleTimer.run();
	}

---

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Debug Terminal Output Samples

1. ISR_8_PWMs_Array_Complex on Arduino AVR Leonardo ATMega32U4

The following is the sample terminal output when running example ISR_8_PWMs_Array_Complex to demonstrate how to use multiple PWM channels with complex callback functions, the accuracy of ISR Hardware PWM-channels, especially when system is very busy. The ISR PWM-channels is running exactly according to corresponding programmed periods and duty-cycles

Starting ISR_8_PWMs_Array_Complex on Arduino AVR ATMega32U4
AVR_Slow_PWM v1.2.3
CPU Frequency = 16 MHz
[PWM] T3
[PWM] Freq * 1000 = 10000000.00
[PWM] F_CPU = 16000000 , preScalerDiv = 1
[PWM] OCR = 1599 , preScalerIndex = 1
[PWM] OK in loop => _OCR = 1599
[PWM] _preScalerIndex = 1 , preScalerDiv = 1
Starting  ITimer3 OK, micros() = 3520328
Channel : 0	Period : 1000000		OnTime : 50000	Start_Time : 3520968
Channel : 1	Period : 500000		OnTime : 50000	Start_Time : 3520968
Channel : 2	Period : 333333		OnTime : 66666	Start_Time : 3520968
Channel : 3	Period : 250000		OnTime : 62500	Start_Time : 3520968
Channel : 4	Period : 200000		OnTime : 60000	Start_Time : 3520968
Channel : 5	Period : 166666		OnTime : 58333	Start_Time : 3520968
Channel : 6	Period : 142857		OnTime : 57142	Start_Time : 3520968
Channel : 7	Period : 125000		OnTime : 56250	Start_Time : 3520968
SimpleTimer (us): 2000, us : 13547548, Dus : 10026624
PWM Channel : 0, prog Period (ms): 1000.00, actual (uS) : 1000000, prog DutyCycle : 5, actual : 5.00
PWM Channel : 1, prog Period (ms): 500.00, actual (uS) : 500016, prog DutyCycle : 10, actual : 10.00
PWM Channel : 2, prog Period (ms): 333.33, actual (uS) : 333396, prog DutyCycle : 20, actual : 19.98
PWM Channel : 3, prog Period (ms): 250.00, actual (uS) : 250028, prog DutyCycle : 25, actual : 24.96
PWM Channel : 4, prog Period (ms): 200.00, actual (uS) : 200192, prog DutyCycle : 30, actual : 29.87
PWM Channel : 5, prog Period (ms): 166.67, actual (uS) : 166792, prog DutyCycle : 35, actual : 34.89
PWM Channel : 6, prog Period (ms): 142.86, actual (uS) : 142992, prog DutyCycle : 40, actual : 39.87
PWM Channel : 7, prog Period (ms): 125.00, actual (uS) : 125192, prog DutyCycle : 45, actual : 44.89
SimpleTimer (us): 2000, us : 23596540, Dus : 10048992
PWM Channel : 0, prog Period (ms): 1000.00, actual (uS) : 1000000, prog DutyCycle : 5, actual : 5.00
PWM Channel : 1, prog Period (ms): 500.00, actual (uS) : 500012, prog DutyCycle : 10, actual : 10.00
PWM Channel : 2, prog Period (ms): 333.33, actual (uS) : 333396, prog DutyCycle : 20, actual : 19.98
PWM Channel : 3, prog Period (ms): 250.00, actual (uS) : 250028, prog DutyCycle : 25, actual : 24.95
PWM Channel : 4, prog Period (ms): 200.00, actual (uS) : 200192, prog DutyCycle : 30, actual : 29.88
PWM Channel : 5, prog Period (ms): 166.67, actual (uS) : 166796, prog DutyCycle : 35, actual : 34.90
PWM Channel : 6, prog Period (ms): 142.86, actual (uS) : 142992, prog DutyCycle : 40, actual : 39.87
PWM Channel : 7, prog Period (ms): 125.00, actual (uS) : 125192, prog DutyCycle : 45, actual : 44.89

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2. ISR_8_PWMs_Array on AVR Mega2560/ADK

The following is the sample terminal output when running example ISR_8_PWMs_Array on AVR Mega2560/ADK to demonstrate how to use multiple PWM channels with simple callback functions.

Starting ISR_8_PWMs_Array on Arduino AVR Mega2560/ADK
AVR_Slow_PWM v1.2.3
CPU Frequency = 16 MHz
[PWM] T3
[PWM] Freq * 1000 = 10000000.00
[PWM] F_CPU = 16000000 , preScalerDiv = 1
[PWM] OCR = 1599 , preScalerIndex = 1
[PWM] OK in loop => _OCR = 1599
[PWM] _preScalerIndex = 1 , preScalerDiv = 1
Starting  ITimer3 OK, micros() = 2023732
Channel : 0	    Period : 1000000		OnTime : 50000	Start_Time : 2031420
Channel : 1	    Period : 500000		OnTime : 50000	Start_Time : 2042728
Channel : 2	    Period : 333333		OnTime : 66666	Start_Time : 2054724
Channel : 3	    Period : 250000		OnTime : 62500	Start_Time : 2067932
Channel : 4	    Period : 200000		OnTime : 60000	Start_Time : 2084232
Channel : 5	    Period : 166666		OnTime : 58333	Start_Time : 2115432
Channel : 6	    Period : 142857		OnTime : 57142	Start_Time : 3075536
Channel : 7	    Period : 125000		OnTime : 56250	Start_Time : 4221280

---

3. ISR_8_PWMs_Array_Simple on Arduino AVR Nano

The following is the sample terminal output when running example ISR_8_PWMs_Array_Simple on Arduino AVR UNO to demonstrate how to use multiple PWM channels.

Starting ISR_8_PWMs_Array_Complex on Arduino AVR UNO, Nano, etc.
AVR_Slow_PWM v1.2.3
CPU Frequency = 16 MHz
[PWM] T1
[PWM] Freq * 1000 = 10000000.00
[PWM] F_CPU = 16000000 , preScalerDiv = 1
[PWM] OCR = 1599 , preScalerIndex = 1
[PWM] OK in loop => _OCR = 1599
[PWM] _preScalerIndex = 1 , preScalerDiv = 1
[PWM] TCCR1B = 9
Starting  ITimer1 OK, micros() = 2025876
Channel : 0	Period : 1000000		OnTime : 50000	Start_Time : 2026740
Channel : 1	Period : 500000		OnTime : 50000	Start_Time : 2026740
Channel : 2	Period : 333333		OnTime : 66666	Start_Time : 2026740
Channel : 3	Period : 250000		OnTime : 62500	Start_Time : 2026740
Channel : 4	Period : 200000		OnTime : 60000	Start_Time : 2026740
Channel : 5	Period : 166666		OnTime : 58333	Start_Time : 2026740
Channel : 6	Period : 142857		OnTime : 57142	Start_Time : 2026740
Channel : 7	Period : 125000		OnTime : 56250	Start_Time : 2026740
SimpleTimer (us): 2000, us : 12072128, Dus : 10045452
PWM Channel : 0, prog Period (ms): 1000.00, actual (uS) : 1000000, prog DutyCycle : 5, actual : 5.00
PWM Channel : 1, prog Period (ms): 500.00, actual (uS) : 500012, prog DutyCycle : 10, actual : 10.00
PWM Channel : 2, prog Period (ms): 333.33, actual (uS) : 333396, prog DutyCycle : 20, actual : 19.98
PWM Channel : 3, prog Period (ms): 250.00, actual (uS) : 250024, prog DutyCycle : 25, actual : 24.95
PWM Channel : 4, prog Period (ms): 200.00, actual (uS) : 200208, prog DutyCycle : 30, actual : 29.96
PWM Channel : 5, prog Period (ms): 166.67, actual (uS) : 166792, prog DutyCycle : 35, actual : 34.90
PWM Channel : 6, prog Period (ms): 142.86, actual (uS) : 142992, prog DutyCycle : 40, actual : 39.87
PWM Channel : 7, prog Period (ms): 125.00, actual (uS) : 125192, prog DutyCycle : 45, actual : 44.89
SimpleTimer (us): 2000, us : 22147164, Dus : 10075036
PWM Channel : 0, prog Period (ms): 1000.00, actual (uS) : 1000000, prog DutyCycle : 5, actual : 5.00
PWM Channel : 1, prog Period (ms): 500.00, actual (uS) : 500012, prog DutyCycle : 10, actual : 10.00
PWM Channel : 2, prog Period (ms): 333.33, actual (uS) : 333396, prog DutyCycle : 20, actual : 19.98
PWM Channel : 3, prog Period (ms): 250.00, actual (uS) : 250196, prog DutyCycle : 25, actual : 24.94
PWM Channel : 4, prog Period (ms): 200.00, actual (uS) : 199996, prog DutyCycle : 30, actual : 30.00
PWM Channel : 5, prog Period (ms): 166.67, actual (uS) : 166792, prog DutyCycle : 35, actual : 34.90
PWM Channel : 6, prog Period (ms): 142.86, actual (uS) : 143012, prog DutyCycle : 40, actual : 39.87
PWM Channel : 7, prog Period (ms): 125.00, actual (uS) : 125012, prog DutyCycle : 45, actual : 44.95

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4. ISR_Modify_PWM on AVR Mega2560/ADK

The following is the sample terminal output when running example ISR_Modify_PWM on AVR Mega2560/ADK to demonstrate how to modify PWM settings on-the-fly without deleting the PWM channel

Starting ISR_Modify_PWM on Arduino AVR Mega2560/ADK
AVR_Slow_PWM v1.2.3
CPU Frequency = 16 MHz
[PWM] T3
[PWM] Freq * 1000 = 10000000.00
[PWM] F_CPU = 16000000 , preScalerDiv = 1
[PWM] OCR = 1599 , preScalerIndex = 1
[PWM] OK in loop => _OCR = 1599
[PWM] _preScalerIndex = 1 , preScalerDiv = 1
Starting  ITimer3 OK, micros() = 2023764
Using PWM Freq = 200.00, PWM DutyCycle = 1.00
Channel : 0	    Period : 5000		OnTime : 50	Start_Time : 2038456
Channel : 0	    Period : 10000		OnTime : 555	Start_Time : 12052172
Channel : 0	    Period : 5000		OnTime : 50	Start_Time : 22052172
Channel : 0	    Period : 10000		OnTime : 555	Start_Time : 32052172
Channel : 0	    Period : 5000		OnTime : 50	Start_Time : 42057172
Channel : 0	    Period : 10000		OnTime : 555	Start_Time : 52057180
Channel : 0	    Period : 5000		OnTime : 50	Start_Time : 62057372
Channel : 0	    Period : 10000		OnTime : 555	Start_Time : 72057372
Channel : 0	    Period : 5000		OnTime : 50	Start_Time : 82057376
Channel : 0	    Period : 10000		OnTime : 555	Start_Time : 92057572
Channel : 0	    Period : 5000		OnTime : 50	Start_Time : 102062572
Channel : 0	    Period : 10000		OnTime : 555	Start_Time : 112062572
Channel : 0	    Period : 5000		OnTime : 50	Start_Time : 122062572
Channel : 0	    Period : 10000		OnTime : 555	Start_Time : 132062572
Channel : 0	    Period : 5000		OnTime : 50	Start_Time : 142067572
Channel : 0	    Period : 10000		OnTime : 555	Start_Time : 152062572

---

5. ISR_Changing_PWM on AVR Mega2560/ADK

The following is the sample terminal output when running example ISR_Changing_PWM on AVR Mega2560/ADK to demonstrate how to modify PWM settings on-the-fly by deleting the PWM channel and reinit the PWM channel

Starting ISR_Changing_PWM on Arduino AVR Mega2560/ADK
AVR_Slow_PWM v1.2.3
CPU Frequency = 16 MHz
[PWM] T3
[PWM] Freq * 1000 = 10000000.00
[PWM] F_CPU = 16000000 , preScalerDiv = 1
[PWM] OCR = 1599 , preScalerIndex = 1
[PWM] OK in loop => _OCR = 1599
[PWM] _preScalerIndex = 1 , preScalerDiv = 1
Starting  ITimer3 OK, micros() = 2023844
Using PWM Freq = 1.00, PWM DutyCycle = 50.00
Using PWM Freq = 2.00, PWM DutyCycle = 90.00
Using PWM Freq = 1.00, PWM DutyCycle = 50.00
Using PWM Freq = 2.00, PWM DutyCycle = 90.00
Using PWM Freq = 1.00, PWM DutyCycle = 50.00
Using PWM Freq = 2.00, PWM DutyCycle = 90.00

---

---

Debug

Debug is enabled by default on Serial.

You can also change the debugging level _PWM_LOGLEVEL_ from 0 to 4

// Don't define _PWM_LOGLEVEL_ > 0. Only for special ISR debugging only. Can hang the system.
#define _PWM_LOGLEVEL_     0

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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.

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Issues

Submit issues to: AVR_Slow_PWM issues

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TO DO

1. Search for bug and improvement.
2. Similar features for remaining Arduino boards

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DONE

1. Basic hardware multi-channel PWM for AVR boards, such as Mega-2560, UNO,Nano, Leonardo, etc. using AVR core
2. Add Table of Contents
3. Add functions to modify PWM settings on-the-fly
4. Fix multiple-definitions linker error. Drop src_cpp and src_h directories
5. Add example multiFileProject to demo for multiple-file project
6. Improve accuracy by using float, instead of uint32_t for dutycycle
7. Optimize library code by using reference-passing instead of value-passing
8. DutyCycle to be optionally updated at the end current PWM period instead of immediately.
9. Display informational warning only when _PWM_LOGLEVEL_ > 3

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Contributions and Thanks

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

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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

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License

• The library is licensed under MIT

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Copyright

Copyright (c) 2021- Khoi Hoang