MBED_RP2040_PWM Library

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Table of Contents

• Why do we need this MBED_RP2040_PWM library
  • Features
  • Currently supported Boards
• Changelog
• Prerequisites
• Installation
  • Use Arduino Library Manager
  • Manual Install
  • VS Code & PlatformIO
• HOWTO Fix Multiple Definitions Linker Error
• Usage
  • 1. Prepare PWM settings
  • 2. Set PWM Frequency and dutycycle
  • 3. Read actual PWM Parameters
• Examples
  • 1. PWM_Multi
  • 2. PWM_Single
  • 3. multiFileProject. New
• Example PWM_Multi
• Debug Terminal Output Samples
  • 1. PWM_Single on RaspberryPi Pico
  • 2. PWM_Multi on RaspberryPi Pico
• Debug
• Troubleshooting
• Issues
• TO DO
• DONE
• Contributions and Thanks
• Contributing
• License
• Copyright

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Why do we need this MBED_RP2040_PWM library

Features

This library enables you to use Hardware-based PWM to create and output PWM to pins on MBED RP2040-based boards such as Nano_RP2040_Connect, RASPBERRY_PI_PICO, using Arduino-mbed mbed_rp2040 or mbed_nano core

This library is using the same or similar functions as other FastPWM libraries, as follows, to enable you to port your PWM code easily between platforms

1. RP2040_PWM
2. AVR_PWM
3. megaAVR_PWM
4. ESP32_FastPWM
5. SAMD_PWM
6. SAMDUE_PWM
7. nRF52_PWM
8. Teensy_PWM
9. ATtiny_PWM
10. Dx_PWM
11. Portenta_H7_PWM
12. MBED_RP2040_PWM
13. nRF52_MBED_PWM
14. STM32_PWM

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The most important feature is they're purely hardware-based PWM channels. Therefore, the frequency can be higher than hybrid or software-based PWM, and their executions are not blocked by bad-behaving functions / tasks. This important feature is absolutely necessary for mission-critical tasks.

The PWM_Multi will demonstrate the usage of multichannel PWM using multiple Hardware Timers. The 4 independent Hardware Timers are used to control 4 different PWM outputs, with totally independent frequencies and dutycycles. You can start, stop, change and restore the settings of any PWM channel on-the-fly.

Being hardware-based PWM, their executions are not blocked by bad-behaving functions / tasks, such as connecting to WiFi, Internet or Blynk services.

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

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Currently supported Boards

1. RP2040-based boards such as Nano_RP2040_Connect, RASPBERRY_PI_PICO, ADAFRUIT_FEATHER_RP2040 and GENERIC_RP2040, etc. using Arduino-mbed RP2040 core

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Prerequisites

1. Arduino IDE 1.8.19+ for Arduino.
2. Arduino mbed_rp2040 core 3.4.1+ for Arduino (Use Arduino Board Manager) RP2040-based boards, such as Arduino Nano RP2040 Connect, RASPBERRY_PI_PICO, etc..

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Installation

Use Arduino Library Manager

The best and easiest way is to use Arduino Library Manager. Search for MBED_RP2040_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 MBED_RP2040_PWM page.
2. Download the latest release MBED_RP2040_PWM-main.zip.
3. Extract the zip file to MBED_RP2040_PWM-main directory
4. Copy whole MBED_RP2040_PWM-main folder to Arduino libraries' directory such as ~/Arduino/libraries/.

VS Code & PlatformIO

1. Install VS Code
2. Install PlatformIO
3. Install MBED_RP2040_PWM library by using Library Manager. Search for MBED_RP2040_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 "MBED_RP2040_PWM.hpp"    //https://github.com/khoih-prog/MBED_RP2040_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 "MBED_RP2040_PWM.h"      //https://github.com/khoih-prog/MBED_RP2040_PWM

Check the new multiFileProject example for a HOWTO demo.

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Usage

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

1. Prepare PWM settings

// Valid pins from 0-29 (GP0-GP29)
uint32_t myPin  = 15;    // GP15

float dutyCycle = 50.0f;

float freq      = 5000.0f;

mbed::PwmOut* pwm   = NULL;

2. Set PWM Frequency and dutycycle

void setup()
{
  ....
  
  setPWM(pwm, myPin, freq, dutyCycle);
}  

3. Read actual PWM Parameters

Use these functions

float getFreq(mbed::PwmOut* &pwm);

float getDutyCycle(mbed::PwmOut* &pwm);

float getPulseWidth_uS(mbed::PwmOut* &pwm);

float getPeriod_uS(mbed::PwmOut* &pwm);

For example

// Valid pins from 0-29 (GP0-GP29)
uint32_t myPin  = 15;    // GP15

float dutyCycle = 50.0f;

float freq      = 5000.0f;

mbed::PwmOut* pwm   = NULL;

setPWM(pwm, myPin, freq, dutyCycle);

if (pwm)
{
  Serial.print(getPulseWidth_uS(pwm)); Serial.print(F("\t\t"));
  Serial.print(getDutyCycle(pwm)); Serial.print(F("\t\t"));
  Serial.print(getPeriod_uS(pwm));
}

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Examples:

1. PWM_Multi
2. PWM_Single
3. multiFileProject New

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Example PWM_Multi

#if !( defined(ARDUINO_NANO_RP2040_CONNECT) || defined(ARDUINO_RASPBERRY_PI_PICO) || defined(ARDUINO_ADAFRUIT_FEATHER_RP2040) || \
      defined(ARDUINO_GENERIC_RP2040) ) && defined(ARDUINO_ARCH_MBED)
  #error This code is intended to run on the MBED RP2040 platform! Please check your Tools->Board setting.
#endif

#define _PWM_LOGLEVEL_       1

// To be included only in main(), .ino with setup() to avoid `Multiple Definitions` Linker Error
#include "MBED_RP2040_PWM.h"

#define LED_ON        LOW
#define LED_OFF       HIGH

#ifndef LED_BUILTIN
  #define LED_BUILTIN       25
#endif

#ifndef LED_BLUE
  #define LED_BLUE          10
#endif

#ifndef LED_RED
  #define LED_RED           11
#endif

// Valid pins from 0-29 (GP0-GP29)
uint32_t pins[]       = { 12, 13, 14, 15 };

#define NUM_OF_PINS       ( sizeof(pins) / sizeof(uint32_t) )

float dutyCycle[]      = { 50.0f, 50.0f, 50.0f, 50.0f };

float freq[]           = { 1000.0f, 2500.0f, 4000.0f, 5000.0f };

float curDutyCycle[]   = { 50.0f, 50.0f, 50.0f, 50.0f };

float curFreq[]        = { 1000.0f, 2500.0f, 4000.0f, 5000.0f };

mbed::PwmOut* pwm[]    = { NULL, NULL, NULL, NULL };

void startAllPWM()
{
  digitalWrite(LED_BUILTIN, LED_ON);
  digitalWrite(LED_BLUE, LED_OFF);
  digitalWrite(LED_RED, LED_OFF);
  
  for (uint8_t index = 0; index < NUM_OF_PINS; index++)
  {
    PWM_LOGERROR7("Freq = ", freq[index], ", \tDutyCycle % = ", dutyCycle[index], ", \tDutyCycle = ", dutyCycle[index] / 100, ", \tPin = GP", pins[index]);
    
    // setPWM(mbed::PwmOut* &pwm, pinsize_t pin, float frequency, float dutyCycle)
    setPWM(pwm[index], pins[index], freq[index], dutyCycle[index]);
  }
}

void restoreAllPWM()
{
  digitalWrite(LED_BUILTIN, LED_ON);
  digitalWrite(LED_BLUE, LED_OFF);
  digitalWrite(LED_RED, LED_OFF);
  
  for (uint8_t index = 0; index < NUM_OF_PINS; index++)
  {
    curFreq[index]      = freq[index];
    curDutyCycle[index] = dutyCycle[index];
    
    // setPWM(mbed::PwmOut* &pwm, pinsize_t pin, float frequency, float dutyCycle)
    setPWM(pwm[index], pins[index], freq[index], dutyCycle[index]);
  }
}

void changeAllPWM()
{
  digitalWrite(LED_BUILTIN, LED_OFF);
  digitalWrite(LED_BLUE, LED_ON);
  digitalWrite(LED_RED, LED_OFF);
  
  for (uint8_t index = 0; index < NUM_OF_PINS; index++)
  {
    curFreq[index]      = freq[index] * 2;
    curDutyCycle[index] = dutyCycle[index] / 2;
    
    // setPWM(mbed::PwmOut* &pwm, pinsize_t pin, float frequency, float dutyCycle)
    setPWM(pwm[index], pins[index], curFreq[index], curDutyCycle[index]);
  }
}

void stopAllPWM()
{
  digitalWrite(LED_BUILTIN, LED_OFF);
  digitalWrite(LED_BLUE, LED_OFF);
  digitalWrite(LED_RED, LED_ON);
  
  for (uint8_t index = 0; index < NUM_OF_PINS; index++)
  {
    curFreq[index]      = 1000.0f;
    curDutyCycle[index] = 0.0f;
    
    //stopPWM(mbed::PwmOut* &pwm, pinsize_t pin)
    stopPWM(pwm[index], pins[index]);
  }
}

void printLine()
{
  Serial.println(F("\n========================================================="));
}

void printPulseWidth()
{
  static uint32_t num = 0;

  if (num++ % 50 == 0)
  {
    printLine();
    
    for (uint8_t index = 0; index < NUM_OF_PINS; index++)
    {
      Serial.print(F("PW (us) ")); Serial.print(index); Serial.print(F("\t"));  
    }

    printLine();
  }
 
  if (num > 1)
  {
    for (uint8_t index = 0; index < NUM_OF_PINS; index++)
    {
      if (pwm[index])
      {
        Serial.print(getPulseWidth_uS(pwm[index])); Serial.print(F("\t\t"));
      }
    }

    Serial.println();
  }
}

#define PRINT_INTERVAL      10000L
#define CHANGE_INTERVAL     20000L

void check_status()
{
  static unsigned long checkstatus_timeout  = 0;
  static unsigned long changePWM_timeout    = 0;

  static bool PWM_orig  = true;
  static uint32_t count = 0;

  // Print every PRINT_INTERVAL (10) seconds.
  if ((millis() > checkstatus_timeout) || (checkstatus_timeout == 0))
  {
    printPulseWidth();
    checkstatus_timeout = millis() + PRINT_INTERVAL;
  }

  if ( (millis() > changePWM_timeout) && (millis() > CHANGE_INTERVAL) )
  {
    
    if (PWM_orig)
    {
      if (count++ %2 == 0)
      {
        Serial.println("Stop all PWM");
        stopAllPWM();
      }
      else
      {
        Serial.println("Change all PWM");
        
        changeAllPWM();

        PWM_orig = !PWM_orig;
      }
    }
    else
    {
      Serial.println("Restore all PWM");
      
      restoreAllPWM();

      PWM_orig = !PWM_orig;
    }
      
    changePWM_timeout = millis() + CHANGE_INTERVAL;
  }
}

void setup()
{
  pinMode(LED_BUILTIN, OUTPUT);
  pinMode(LED_BLUE, OUTPUT);
  pinMode(LED_RED, OUTPUT);

  digitalWrite(LED_BUILTIN, LED_OFF);
  digitalWrite(LED_BLUE, LED_OFF);
  digitalWrite(LED_RED, LED_OFF);

  for (uint8_t index = 0; index < NUM_OF_PINS; index++)
  {
    pinMode(pins[index], OUTPUT);
    digitalWrite(pins[index], LOW);
  }

  Serial.begin(115200);
  while (!Serial);

  delay(100);

  Serial.print(F("\nStarting PWM_Multi on ")); Serial.println(BOARD_NAME);
  Serial.println(MBED_RP2040_PWM_VERSION);

  // Automatically retrieve TIM instance and channel associated to pin
  // This is used to be compatible with all STM32 series automatically.

  startAllPWM();
}

void loop()
{
  check_status();
}

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Debug Terminal Output Samples

1. PWM_Single on RaspberryPi Pico

The following is the sample terminal output when running example PWM_Single on RaspberryPi Pico to demonstrate how to start a single PWM channel, then stop, change, restore the PWM settings on-the-fly.

Starting PWM_Single on RaspberryPi Pico
MBED_RP2040_PWM v1.0.0
[PWM] Freq = 5000.00, DutyCycle % = 50.00, DutyCycle = 0.50, Pin = 15

============================================
PW (us)		DutyCycle	Period (uS)
============================================
100.00		50.00		200.00
Stop PWM
0.00		0.00		1000.00
0.00		0.00		1000.00
Change PWM
25.00		25.00		100.00
25.00		25.00		100.00
Restore PWM
100.00		50.00		200.00
100.00		50.00		200.00
Stop PWM
0.00		0.00		1000.00
0.00		0.00		1000.00
Change PWM
25.00		25.00		100.00
25.00		25.00		100.00

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2. PWM_Multi on RaspberryPi Pico

The following is the sample terminal output when running example PWM_Multi on RaspberryPi Pico to demonstrate how to start multiple PWM channels, then stop, change, restore the PWM settings on-the-fly.

Starting PWM_Multi on RaspberryPi Pico
MBED_RP2040_PWM v1.0.0
[PWM] Freq = 1000.00, 	DutyCycle % = 50.00, 	DutyCycle = 0.50, 	Pin = GP12
[PWM] Freq = 2500.00, 	DutyCycle % = 50.00, 	DutyCycle = 0.50, 	Pin = GP13
[PWM] Freq = 4000.00, 	DutyCycle % = 50.00, 	DutyCycle = 0.50, 	Pin = GP14
[PWM] Freq = 5000.00, 	DutyCycle % = 50.00, 	DutyCycle = 0.50, 	Pin = GP15

=========================================================
PW (us) 0	PW (us) 1	PW (us) 2	PW (us) 3	
=========================================================
500.00		200.00		125.00		100.00		
Stop all PWM
0.00		0.00		0.00		0.00		
0.00		0.00		0.00		0.00		
Change all PWM
125.00		50.00		31.25		25.00		
125.00		50.00		31.25		25.00		
Restore all PWM
500.00		200.00		125.00		100.00		
500.00		200.00		125.00		100.00		
Stop all PWM
0.00		0.00		0.00		0.00		
0.00		0.00		0.00		0.00		
Change all PWM
125.00		50.00		31.25		25.00		
125.00		50.00		31.25		25.00		
Restore all PWM
500.00		200.00		125.00		100.00		
500.00		200.00		125.00		100.00		

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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: MBED_RP2040_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 Nano_RP2040_Connect and RASPBERRY_PI_PICO, etc. using Arduino-mbed core
2. Add Table of Contents
3. Permit to start, stop, modify, restore PWM settings on-the-fly
4. Optimize library code by using reference-passing instead of value-passing
5. Use h-only style
6. Add functions to read PWM parameters.

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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) 2022- Khoi Hoang