ISR_Changing_PWM.ino

/****************************************************************************************************************************
  ISR_Changing_PWM.ino
  For Teensy boards (Teensy 2.x, Teensy LC, Teensy 3.x, Teensy 4.x, etc.)
  Written by Khoi Hoang

  Built by Khoi Hoang https://github.com/khoih-prog/Teensy_Slow_PWM
  Licensed under MIT license

  Now even you use all these new 16 ISR-based timers,with their maximum interval practically unlimited (limited only by
  unsigned long miliseconds), you just consume only one  RP2040-based timer and avoid conflicting with other cores' tasks.
  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.
*****************************************************************************************************************************/

#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"

#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        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        0.0333f
  #define HW_TIMER_INTERVAL_FREQ      30000L
#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 USING_PWM_FREQUENCY     true

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

// You can assign pins here. Be carefull to select good pin to use or crash
//uint32_t PWM_Pin    = LED_BUILTIN;
uint32_t PWM_Pin    = 3;    //LED_BUILTIN;

// You can assign any interval for any timer here, in Hz
float PWM_Freq1   = 1.0f;
// You can assign any interval for any timer here, in Hz
float PWM_Freq2   = 2.0f;

// You can assign any interval for any timer here, in microseconds
uint32_t PWM_Period1 = 1000000 / PWM_Freq1;
// You can assign any interval for any timer here, in microseconds
uint32_t PWM_Period2 = 1000000 / PWM_Freq2;

// You can assign any duty_cycle for any PWM here, from 0-100
float PWM_DutyCycle1  = 50.0;
// You can assign any duty_cycle for any PWM here, from 0-100
float PWM_DutyCycle2  = 90.0;

// Channel number used to identify associated channel
int channelNum;

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

void setup()
{
  Serial.begin(115200);

  while (!Serial);

  delay(2000);

  Serial.print(F("\nStarting ISR_Changing_PWM 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
}

void loop()
{
  Serial.print(F("Using PWM Freq = "));
  Serial.print(PWM_Freq1);
  Serial.print(F(", PWM DutyCycle = "));
  Serial.println(PWM_DutyCycle1);

#if USING_PWM_FREQUENCY

  // You can use this with PWM_Freq in Hz
  channelNum = ISR_PWM.setPWM(PWM_Pin, PWM_Freq1, PWM_DutyCycle1);

#else
#if USING_MICROS_RESOLUTION
  // Or using period in microsecs resolution
  channelNum = ISR_PWM.setPWM_Period(PWM_Pin, PWM_Period1, PWM_DutyCycle1);
#else
  // Or using period in millisecs resolution
  channelNum = ISR_PWM.setPWM_Period(PWM_Pin, PWM_Period1 / 1000, PWM_DutyCycle1);
#endif
#endif

  delay(10000);

  ISR_PWM.deleteChannel((unsigned) channelNum);

  Serial.print(F("Using PWM Freq = "));
  Serial.print(PWM_Freq2);
  Serial.print(F(", PWM DutyCycle = "));
  Serial.println(PWM_DutyCycle2);

#if USING_PWM_FREQUENCY

  // You can use this with PWM_Freq in Hz
  channelNum = ISR_PWM.setPWM(PWM_Pin, PWM_Freq2, PWM_DutyCycle2);

#else
#if USING_MICROS_RESOLUTION
  // Or using period in microsecs resolution
  channelNum = ISR_PWM.setPWM_Period(PWM_Pin, PWM_Period2, PWM_DutyCycle2);
#else
  // Or using period in millisecs resolution
  channelNum = ISR_PWM.setPWM_Period(PWM_Pin, PWM_Period2 / 1000, PWM_DutyCycle2);
#endif
#endif

  delay(10000);

  ISR_PWM.deleteChannel((unsigned) channelNum);
}