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This library enables you to use ISR-based PWM channels on Teensy boards, such as Teensy 2.x, Teensy LC, Teensy 3.x, Teensy 4.x, Teensy MicroMod, etc., to create and output PWM any GPIO pin. It now supports 16 ISR-based PWM channels, while consuming only 1 Hardware Timer. PWM channel interval can be very long (ulong microsecs / millisecs). The most important feature is they're ISR-based PWM channels, supporting lower PWM frequencies with suitable accuracy. Their executions are not blocked by bad-behaving functions or tasks. This important feature is absolutely necessary for mission-critical tasks. These ISR-based PWMs, still work even if other software functions are blocking. Moreover, they are much more precise (certainly depending on clock frequency accuracy) than other software-based PWM using millis() or micros(). That's necessary if you need to control devices requiring high precision

License: MIT License

C++ 77.57% C 22.24% Shell 0.19%
isr pwm pwm-driver duty-cycle timer-interrupt hardware-timer isr-based isr-based-pmw multi-channel-pwm synchronized-pwm

teensy_slow_pwm's Introduction

Teensy_Slow_PWM Library

arduino-library-badge GitHub release GitHub contributions welcome GitHub issues

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Table of Contents

Important Change from v1.2.0

Please have a look at HOWTO Fix Multiple Definitions Linker Error

As more complex calculation and check inside ISR are introduced from v1.2.0, there is possibly some crash depending on use-case.

You can modify to use larger HW_TIMER_INTERVAL_US, (from current 10 / 20 / 100uS), according to your board and use-case if crash happens.

#if defined(__IMXRT1062__)
  // For Teensy 4.0 and 4.1
  // Don't change these numbers to make higher Timer freq. System can hang
  #define HW_TIMER_INTERVAL_MS        0.01f
  #define HW_TIMER_INTERVAL_FREQ      100000L
#elif defined(__MK66FX1M0__)
  // For Teensy 3.6
  // Don't change these numbers to make higher Timer freq. System can hang
  #define HW_TIMER_INTERVAL_MS        0.05f
  #define HW_TIMER_INTERVAL_FREQ      20000L
#else
  // 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
#endif

Why do we need this Teensy_Slow_PWM library

Features

This library enables you to use ISR-based PWM channels on Teensy boards, such as Teensy 2.x, Teensy LC, Teensy 3.x, Teensy 4.x, Teensy MicroMod, etc., etc. using Teensyduno 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 change the PWM settings on-the-fly

This library enables you to use Interrupt from Hardware Timers on Teensy 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).

You'd certainly experienced that if using other Hardware Timer Libraries, such as TimerOne or TimerThree, the interval is short, in milliseconds range.

For example, Teensy 4.x, with super-high clock frequency of 600MHz and Timer1 and Timer3 clock of 150MHz, the maximum interval / frequency is only 55922.3467 us / 17.881939 Hz. This Teensy_Slow_PWM library will provide you up to 16 super-long (ulong millisecs) ISR-based PWM-channels for each used Timer1 or Timer3.

For Teensy 4.x, this library will be expanded to use other available hardware timers, such as FTM, GPT, QUAD, PIT, in addition to current Timer1 and Timer3.

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

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

Currently supported Boards

  1. Teensy boards such as :
  • Teensy 4.1, Teensy MicroMod, Teensy 4.0
  • Teensy 3.6, 3.5, 3.2/3.1, 3.0
  • Teensy LC
  • Teensy++ 2.0 and Teensy 2.0

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.

Prerequisites

  1. Arduino IDE 1.8.19+ for Arduino. GitHub release

  2. Teensy Core 1.57+ for Teensy.

  3. To use with certain example

Installation

Use Arduino Library Manager

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

Manual Install

Another way to install is to:

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

VS Code & PlatformIO

  1. Install VS Code
  2. Install PlatformIO
  3. Install Teensy_Slow_PWM library by using Library Manager. Search for Teensy_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

Packages' Patches

1. For Teensy boards

To be able to compile and run on Teensy boards, you have to copy the file Teensy boards.txt into Teensy hardware directory (./arduino-1.8.19/hardware/teensy/avr/boards.txt).

Supposing the Arduino version is 1.8.19. These files must be copied into the directory:

  • ./arduino-1.8.19/hardware/teensy/avr/boards.txt
  • ./arduino-1.8.19/hardware/teensy/avr/cores/teensy/Stream.h
  • ./arduino-1.8.19/hardware/teensy/avr/cores/teensy3/Stream.h
  • ./arduino-1.8.19/hardware/teensy/avr/cores/teensy4/Stream.h

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:

  • ./arduino-x.yy.zz/hardware/teensy/avr/boards.txt
  • ./arduino-x.yy.zz/hardware/teensy/avr/cores/teensy/Stream.h
  • ./arduino-x.yy.zz/hardware/teensy/avr/cores/teensy3/Stream.h
  • ./arduino-x.yy.zz/hardware/teensy/avr/cores/teensy4/Stream.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 this .hpp file

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

Usage

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

1. Init Hardware Timer

// You can select Teensy Hardware Timer from TEENSY_TIMER_1 or TEENSY_TIMER_3

// Init Teensy timer TEENSY_TIMER_1
TeensyTimer ITimer(TEENSY_TIMER_1);

// Init Teensy_SLOW_PWM, each can service 16 different ISR-based PWM channels
Teensy_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);
                   
  ....                 
}

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

Teensy_Slow_PWM/examples/ISR_8_PWMs_Array_Complex/ISR_8_PWMs_Array_Complex.ino

Lines 16 to 469 in cdd23d2

#if !( defined(CORE_TEENSY) || defined(TEENSYDUINO) )
#error This code is designed to run on Teensy platform! Please check your Tools->Board setting.
#endif
// These define's must be placed at the beginning before #include "Teensy_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
#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 "Teensy_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
#if defined(__IMXRT1062__)
// For Teensy 4.0 and 4.1
// Don't change these numbers to make higher Timer freq. System can hang
#define HW_TIMER_INTERVAL_MS 0.01f
#define HW_TIMER_INTERVAL_FREQ 100000L
#elif defined(__MK66FX1M0__)
// For Teensy 3.6
// Don't change these numbers to make higher Timer freq. System can hang
#define HW_TIMER_INTERVAL_MS 0.05f
#define HW_TIMER_INTERVAL_FREQ 20000L
#else
// 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
#endif
volatile uint32_t startMicros = 0;
// You can select Teensy Hardware Timer from TEENSY_TIMER_1 or TEENSY_TIMER_3
// Init Teensy timer TEENSY_TIMER_1
TeensyTimer ITimer(TEENSY_TIMER_1);
// Init Teensy_SLOW_PWM, each can service 16 different ISR-based PWM channels
Teensy_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[] =
{
1000L, 500L, 333L, 250L, 200L, 166L, 142L, 125L
};
// You can assign any interval for any timer here, in Hz
// 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, 30.0, 40.0, 45.0, 50.0, 55.0
};
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, 5, 0, 0, 0, 0 },
{ PIN_D0, doingSomethingStart1, doingSomethingStop1, 2, 10, 0, 0, 0, 0 },
{ PIN_D1, doingSomethingStart2, doingSomethingStop2, 3, 20, 0, 0, 0, 0 },
{ PIN_D2, doingSomethingStart3, doingSomethingStop3, 4, 30, 0, 0, 0, 0 },
{ PIN_D3, doingSomethingStart4, doingSomethingStop4, 5, 40, 0, 0, 0, 0 },
{ PIN_D4, doingSomethingStart5, doingSomethingStop5, 6, 45, 0, 0, 0, 0 },
{ PIN_D5, doingSomethingStart6, doingSomethingStop6, 7, 50, 0, 0, 0, 0 },
{ PIN_D6, doingSomethingStart7, doingSomethingStop7, 8, 55, 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.f / curISR_PWM_Data[i].PWM_Freq);
Serial.print(F(", actual : ")); Serial.print((uint32_t) 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 / 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(TEENSY_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
// Interval in microsecs
if (ITimer.attachInterruptInterval(HW_TIMER_INTERVAL_MS * 1000, TimerHandler))
{
startMicros = micros();
Serial.print(F("Starting ITimer OK, micros() = ")); Serial.println(startMicros);
}
else
Serial.println(F("Can't set ITimer correctly. Select another freq. or interval"));
#else
if (ITimer.attachInterrupt(HW_TIMER_INTERVAL_FREQ, TimerHandler))
{
Serial.print(F("Starting ITimer OK, micros() = ")); Serial.println(micros());
}
else
Serial.println(F("Can't set ITimer. Select another freq. or timer"));
#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();
}

Debug Terminal Output Samples

1. ISR_8_PWMs_Array_Complex on Teensy 4.1

The following is the sample terminal output when running example ISR_8_PWMs_Array_Complex on Teensy 4.1 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 Teensy 4.1
Teensy_Slow_PWM v1.2.1
CPU Frequency = 600 MHz
[PWM] TEENSY_TIMER_1: , F_BUS_ACTUAL (MHz) = 150
[PWM] Request interval = 10 , actual interval (us) = 10
[PWM] Prescale = 0 , _timerCount = 750
Starting  ITimer OK, micros() = 3017009
Channel : 0	    Period : 1000000		OnTime : 50000	Start_Time : 3017012
Channel : 1	    Period : 500000		OnTime : 50000	Start_Time : 3017017
Channel : 2	    Period : 333333		OnTime : 66666	Start_Time : 3017022
Channel : 3	    Period : 250000		OnTime : 75000	Start_Time : 3017027
Channel : 4	    Period : 200000		OnTime : 80000	Start_Time : 3017032
Channel : 5	    Period : 166666		OnTime : 74999	Start_Time : 3017037
Channel : 6	    Period : 142857		OnTime : 71428	Start_Time : 3017043
Channel : 7	    Period : 125000		OnTime : 68750	Start_Time : 3017048
SimpleTimer (us): 2000, us : 13017053, Dus : 10000043
PWM Channel : 0, prog Period (ms): 1000.00, actual : 1000006, prog DutyCycle : 5.00, actual : 5.00
PWM Channel : 1, prog Period (ms): 500.00, actual : 500003, prog DutyCycle : 10.00, actual : 10.00
PWM Channel : 2, prog Period (ms): 333.33, actual : 333342, prog DutyCycle : 20.00, actual : 20.00
PWM Channel : 3, prog Period (ms): 250.00, actual : 250006, prog DutyCycle : 30.00, actual : 30.00
PWM Channel : 4, prog Period (ms): 200.00, actual : 200004, prog DutyCycle : 40.00, actual : 40.00
PWM Channel : 5, prog Period (ms): 166.67, actual : 166671, prog DutyCycle : 45.00, actual : 44.99
PWM Channel : 6, prog Period (ms): 142.86, actual : 142865, prog DutyCycle : 50.00, actual : 50.00
PWM Channel : 7, prog Period (ms): 125.00, actual : 125003, prog DutyCycle : 55.00, actual : 55.00
SimpleTimer (us): 2000, us : 23017098, Dus : 10000045
PWM Channel : 0, prog Period (ms): 1000.00, actual : 1000006, prog DutyCycle : 5.00, actual : 5.00
PWM Channel : 1, prog Period (ms): 500.00, actual : 500003, prog DutyCycle : 10.00, actual : 10.00
PWM Channel : 2, prog Period (ms): 333.33, actual : 333342, prog DutyCycle : 20.00, actual : 20.00
PWM Channel : 3, prog Period (ms): 250.00, actual : 250007, prog DutyCycle : 30.00, actual : 30.00
PWM Channel : 4, prog Period (ms): 200.00, actual : 200003, prog DutyCycle : 40.00, actual : 40.00
PWM Channel : 5, prog Period (ms): 166.67, actual : 166671, prog DutyCycle : 45.00, actual : 44.99
PWM Channel : 6, prog Period (ms): 142.86, actual : 142866, prog DutyCycle : 50.00, actual : 50.00
PWM Channel : 7, prog Period (ms): 125.00, actual : 125003, prog DutyCycle : 55.00, actual : 55.00
SimpleTimer (us): 2000, us : 33017142, Dus : 10000044
PWM Channel : 0, prog Period (ms): 1000.00, actual : 1000006, prog DutyCycle : 5.00, actual : 5.00
PWM Channel : 1, prog Period (ms): 500.00, actual : 500003, prog DutyCycle : 10.00, actual : 10.00
PWM Channel : 2, prog Period (ms): 333.33, actual : 333342, prog DutyCycle : 20.00, actual : 20.00
PWM Channel : 3, prog Period (ms): 250.00, actual : 250006, prog DutyCycle : 30.00, actual : 30.00
PWM Channel : 4, prog Period (ms): 200.00, actual : 200003, prog DutyCycle : 40.00, actual : 40.00
PWM Channel : 5, prog Period (ms): 166.67, actual : 166671, prog DutyCycle : 45.00, actual : 44.99
PWM Channel : 6, prog Period (ms): 142.86, actual : 142865, prog DutyCycle : 50.00, actual : 50.00
PWM Channel : 7, prog Period (ms): 125.00, actual : 125004, prog DutyCycle : 55.00, actual : 54.99
SimpleTimer (us): 2000, us : 43017187, Dus : 10000045
PWM Channel : 0, prog Period (ms): 1000.00, actual : 1000006, prog DutyCycle : 5.00, actual : 5.00
PWM Channel : 1, prog Period (ms): 500.00, actual : 500003, prog DutyCycle : 10.00, actual : 10.00
PWM Channel : 2, prog Period (ms): 333.33, actual : 333342, prog DutyCycle : 20.00, actual : 20.00
PWM Channel : 3, prog Period (ms): 250.00, actual : 250007, prog DutyCycle : 30.00, actual : 30.00
PWM Channel : 4, prog Period (ms): 200.00, actual : 200004, prog DutyCycle : 40.00, actual : 40.00
PWM Channel : 5, prog Period (ms): 166.67, actual : 166671, prog DutyCycle : 45.00, actual : 44.99
PWM Channel : 6, prog Period (ms): 142.86, actual : 142865, prog DutyCycle : 50.00, actual : 50.00
PWM Channel : 7, prog Period (ms): 125.00, actual : 125003, prog DutyCycle : 55.00, actual : 55.00

2. ISR_8_PWMs_Array on Teensy 4.1

The following is the sample terminal output when running example ISR_8_PWMs_Array on on Teensy 4.1 to demonstrate how to use multiple PWM channels with simple callback functions.

Starting ISR_8_PWMs_Array on Teensy 4.1
Teensy_Slow_PWM v1.2.1
CPU Frequency = 600 MHz
[PWM] TEENSY_TIMER_1: , F_BUS_ACTUAL (MHz) = 150
[PWM] Request interval = 10 , actual interval (us) = 10
[PWM] Prescale = 0 , _timerCount = 750
Starting ITimer OK, micros() = 2938009
Channel : 0	    Period : 1000000		OnTime : 50000	Start_Time : 2938012
Channel : 1	    Period : 500000		OnTime : 50000	Start_Time : 2938017
Channel : 2	    Period : 333333		OnTime : 66666	Start_Time : 2938022
Channel : 3	    Period : 250000		OnTime : 75000	Start_Time : 2938027
Channel : 4	    Period : 200000		OnTime : 80000	Start_Time : 2938032
Channel : 5	    Period : 166666		OnTime : 74999	Start_Time : 2938037
Channel : 6	    Period : 142857		OnTime : 71428	Start_Time : 2938042
Channel : 7	    Period : 125000		OnTime : 68750	Start_Time : 2938047

3. ISR_8_PWMs_Array_Simple on Teensy 4.1

The following is the sample terminal output when running example ISR_8_PWMs_Array_Simple on on Teensy 4.1 to demonstrate how to use multiple PWM channels.

Starting ISR_8_PWMs_Array_Simple on Teensy 4.1
Teensy_Slow_PWM v1.2.1
CPU Frequency = 600 MHz
[PWM] TEENSY_TIMER_1: , F_BUS_ACTUAL (MHz) = 150
[PWM] Request interval = 10 , actual interval (us) = 10
[PWM] Prescale = 0 , _timerCount = 750
Starting ITimer OK, micros() = 3220009
Channel : 0	    Period : 1000000		OnTime : 50000	Start_Time : 3220012
Channel : 1	    Period : 500000		OnTime : 50000	Start_Time : 3220017
Channel : 2	    Period : 333333		OnTime : 66666	Start_Time : 3220022
Channel : 3	    Period : 250000		OnTime : 75000	Start_Time : 3220027
Channel : 4	    Period : 200000		OnTime : 80000	Start_Time : 3220032
Channel : 5	    Period : 166666		OnTime : 74999	Start_Time : 3220037
Channel : 6	    Period : 142857		OnTime : 71428	Start_Time : 3220043
Channel : 7	    Period : 125000		OnTime : 68750	Start_Time : 3220048

4. ISR_Modify_PWM on Teensy 4.1

The following is the sample terminal output when running example ISR_Modify_PWM on Teensy 4.1 to demonstrate how to modify PWM settings on-the-fly without deleting the PWM channel

Starting ISR_Modify_PWM on Teensy 4.1
Teensy_Slow_PWM v1.2.1
CPU Frequency = 600 MHz
[PWM] TEENSY_TIMER_1: , F_BUS_ACTUAL (MHz) = 150
[PWM] Request interval = 33 , actual interval (us) = 33
[PWM] Prescale = 0 , _timerCount = 2475
Starting ITimer OK, micros() = 2531009
Using PWM Freq = 200.00, PWM DutyCycle = 1.00
Channel : 0	    Period : 5000		OnTime : 50	Start_Time : 2531014
Channel : 0	New Period : 10000		OnTime : 555	Start_Time : 12529921
Channel : 0	New Period : 5000		OnTime : 50	Start_Time : 22525957
Channel : 0	New Period : 10000		OnTime : 555	Start_Time : 32529848
Channel : 0	New Period : 5000		OnTime : 50	Start_Time : 42525884
Channel : 0	New Period : 10000		OnTime : 555	Start_Time : 52534793
Channel : 0	New Period : 5000		OnTime : 50	Start_Time : 62530829
Channel : 0	New Period : 10000		OnTime : 555	Start_Time : 72534720
Channel : 0	New Period : 5000		OnTime : 50	Start_Time : 82530756
Channel : 0	New Period : 10000		OnTime : 555	Start_Time : 92539665
Channel : 0	New Period : 5000		OnTime : 50	Start_Time : 102535701
Channel : 0	New Period : 10000		OnTime : 555	Start_Time : 112539593
Channel : 0	New Period : 5000		OnTime : 50	Start_Time : 122535629

5. ISR_Changing_PWM on Teensy 4.1

The following is the sample terminal output when running example ISR_Changing_PWM on Teensy 4.1 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 Teensy 4.1
Teensy_Slow_PWM v1.2.1
CPU Frequency = 600 MHz
[PWM] TEENSY_TIMER_1: , F_BUS_ACTUAL (MHz) = 150
[PWM] Request interval = 33 , actual interval (us) = 33
[PWM] Prescale = 0 , _timerCount = 2475
Starting ITimer OK, micros() = 3617009
Using PWM Freq = 1.00, PWM DutyCycle = 50.00
Channel : 0	    Period : 1000000		OnTime : 500000	Start_Time : 3617014
Using PWM Freq = 2.00, PWM DutyCycle = 90.00
Channel : 0	    Period : 500000		OnTime : 450000	Start_Time : 13617022
Using PWM Freq = 1.00, PWM DutyCycle = 50.00
Channel : 0	    Period : 1000000		OnTime : 500000	Start_Time : 23617030
Using PWM Freq = 2.00, PWM DutyCycle = 90.00
Channel : 0	    Period : 500000		OnTime : 450000	Start_Time : 33617038
Using PWM Freq = 1.00, PWM DutyCycle = 50.00
Channel : 0	    Period : 1000000		OnTime : 500000	Start_Time : 43617046
Using PWM Freq = 2.00, PWM DutyCycle = 90.00
Channel : 0	    Period : 500000		OnTime : 450000	Start_Time : 53617054
Using PWM Freq = 1.00, PWM DutyCycle = 50.00
Channel : 0	    Period : 1000000		OnTime : 500000	Start_Time : 63617062
Using PWM Freq = 2.00, PWM DutyCycle = 90.00
Channel : 0	    Period : 500000		OnTime : 450000	Start_Time : 73617070

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

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: Teensy_Slow_PWM issues

TO DO

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

DONE

  1. Basic hardware multi-channel PWM for Teensy boards, such as Teensy 2.x, Teensy LC, Teensy 3.x, Teensy 4.x, Teensy MicroMod, etc., etc. using Teensyduno core
  2. Add Table of Contents
  3. Add functions to modify PWM settings on-the-fly
  4. Fix multiple-definitions linker error
  5. Optimize library code by using reference-passing instead of value-passing
  6. Improve accuracy by using float, instead of uint32_t for dutycycle
  7. DutyCycle to be optionally updated at the end current PWM period instead of immediately.
  8. Display informational warning only when _PWM_LOGLEVEL_ > 3

Contributions and Thanks

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

Contributing

If you want to contribute to this project:

  • Report bugs and errors
  • Ask for enhancements
  • Create issues and pull requests
  • Tell other people about this library

License

  • The library is licensed under MIT

Copyright

Copyright (c) 2021- Khoi Hoang

teensy_slow_pwm's People

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teensy_slow_pwm's Issues

Unable to set duty cycle to zero

Describe the bug

I need to set and modify 16 PWM channels in order to create 16 PID controllers for heaters. The frequency is 5 Hz and I need to set the duty cycle in 1 ms steps, 0 to 200 ms.

If I set the duty cycle to 0%, I get a pulse 1 ms long every 200 ms (which is wrong as there should be no pulse at all). For the duty cycle = 1%, I get a pulse 3 ms (again wrong, it should be 2 ms), 2% -- 5 ms, …. 99% -- 199 ms, 100% -- 200 ms

Steps to Reproduce

https://github.com/snagaitsev/PWM_slow/blob/main/slow-pwm-test.ino

Expected behavior

There should not be any pulse at 0% duty cycle.

Actual behavior

At 5 Hz (same behavior happens at other frequencies like 50 Hz):
For the duty cycle of 0%, I get a pulse 1 ms long every 200 ms (which is wrong as there should be no pulse at all). For the duty cycle = 1%, I get a pulse 3 ms (again wrong, it should be 2 ms), 2% -- 5 ms, …. 99% -- 199 ms, 100% -- 200 ms

Debug and AT-command log (if applicable)

A clear and concise description of what you expected to happen.

Screenshots

If applicable, add screenshots to help explain your problem.

Information

Please ensure to specify the following:

Arduino 1.18.19
Teensyduino 1.56
Teensy slow PWM library 1.2.1
Teensy 4.0, 600 MHz
OS: Mint 20

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