PWMAudioMBED.h

 
#pragma once
#if defined(ARDUINO_ARCH_MBED)
#include "AudioPWM/PWMAudioBase.h"
#include "AudioTimer/AudioTimer.h"
#include "mbed.h"
 
namespace audio_tools {
 
// forward declaration
class PWMDriverMBED;
using PWMDriver = PWMDriverMBED;
 
class PWMDriverMBED : public DriverPWMBase {
 public:
  PWMDriverMBED() = default;
 
  // Ends the output
  virtual void end() override {
    TRACED();
    ticker.end();  // it does not hurt to call this even if it has not been
                   // started
    is_timer_started = false;
 
    // stop and release pins
    for (int j = 0; j < audio_config.channels; j++) {
      if (pins[j] != nullptr) {
        pins[j]->suspend();
        delete pins[j];
        pins[j] = nullptr;
      }
    }
    pins.clear();
    // pins.shrink_to_fit();
    deleteBuffer();
  }
 
 protected:
  Vector<mbed::PwmOut*> pins;
  TimerAlarmRepeating ticker;  // calls a callback repeatedly with a timeout
 
  virtual void startTimer() override {
    if (!is_timer_started) {
      TRACED();
      long wait_time = 1000000l / audio_config.sample_rate;
      ticker.setCallbackParameter(this);
      ticker.begin(defaultPWMAudioOutputCallback, wait_time, US);
      is_timer_started = true;
    }
  }
 
  virtual void setupPWM() {
    TRACED();
    unsigned long period =
        1000000l / audio_config.pwm_frequency;  // -> 30.517578125 microseconds
    pins.resize(audio_config.channels);
    for (int j = 0; j < audio_config.channels; j++) {
      LOGD("Processing channel %d", j);
      auto gpio = audio_config.pins()[j];
      mbed::PwmOut* pin = new mbed::PwmOut(digitalPinToPinName(gpio));
      LOGI("PWM Pin: %d", gpio);
      pin->period_us(period);
      pin->write(0.0f);  // 0% duty cycle ->
      pin->resume();     // in case it was suspended before
      pins[j] = pin;
    }
  }
 
  virtual void setupTimer() {}
 
  virtual int maxChannels() { return 16; };
 
  virtual int maxOutputValue() { return 1000; }
 
  virtual void pwmWrite(int channel, int value) {
    float float_value = static_cast<float>(value) / maxOutputValue();
    pins[channel]->write(float_value);  // pwm the value is between 0.0 and 1.0
  }
 
  static void defaultPWMAudioOutputCallback(void* obj) {
    PWMDriverMBED* accessAudioPWM = (PWMDriverMBED*)obj;
    if (accessAudioPWM != nullptr) {
      accessAudioPWM->playNextFrame();
    }
  }
};
 
}  // namespace audio_tools
 
#endif