PWM driver with Beep and PlayNote functionality. More...

#include <bsp_pwm.hpp>

Public Types
enum class	NoteName { C = 0 , Cs , D , Ds , E , F , Fs , G , Gs , A , As , B }
	Musical note names used for MIDI note calculation. More...

Public Member Functions
	PWM (int channel, int frequency_hz=1000, float duty_percent=0.0f, int chip=2)
	Constructor: initializes PWM channel, sets initial frequency and duty cycle.

	~PWM ()
	Destructor: disables PWM output.

void	SetFrequency (uint32_t hz)
	Set the output frequency of PWM.

void	SetDutyCycle (float percent)
	Set the duty cycle of PWM output.

void	Enable ()
	Enable the PWM output signal.

void	Disable ()
	Disable the PWM output signal.

void	Beep (uint32_t freq, uint32_t duration_ms)
	Output a beep with specific frequency and duration.

void	PlayNote (NoteName note, uint32_t octave, uint32_t duration_ms)
	Play a musical note based on note name and octave.

void	SetAlarmConfig (uint32_t freq, uint32_t duration_ms, uint32_t delay_ms)
	Set configuration parameters for alarm beep.

void	TriggerAlarm ()
	Trigger an alarm sound followed by a delay.

Private Member Functions
int	WriteSysfs (const std::string &path, int value) const
	Write an integer value to a sysfs file.

Private Attributes
std::string	chip_path_
	Sysfs path to the PWM chip.

std::string	pwm_path_
	Sysfs path to the PWM channel.

int	period_ns_
	PWM period in nanoseconds.

int	channel_
	PWM channel number.

uint32_t	alarm_freq_ = 1500
	Default alarm frequency in Hz.

uint32_t	alarm_duration_ = 300
	Default alarm duration in ms.

uint32_t	alarm_delay_ = 300
	Default alarm delay in ms.

std::thread	note_thread_
	Background thread for playing notes.

NoteName	note_
	Current note name.

uint32_t	octave_
	Current octave.

uint32_t	duration_ms_
	Duration of note in ms.

std::binary_semaphore	note_sem_ {0}
	Semaphore to trigger note play.

Detailed Description

PWM driver with Beep and PlayNote functionality.

This class controls PWM output on Raspberry Pi 5 using GPIO12 (channel 0) and GPIO13 (channel 1).

⚠️ Requires enabling the following overlay in /boot/firmware/config.txt: dtoverlay=pwm-2chan

Definition at line 21 of file bsp_pwm.hpp.

Member Enumeration Documentation

◆ NoteName

enum class PWM::NoteName

strong

Musical note names used for MIDI note calculation.

Definition at line 27 of file bsp_pwm.hpp.

27{ C = 0, Cs, D, Ds, E, F, Fs, G, Gs, A, As, B };

Constructor & Destructor Documentation

◆ PWM()

PWM::PWM	(	int	channel,
		int	frequency_hz = `1000`,
		float	duty_percent = `0.0f`,
		int	chip = `2`
	)

inline

Constructor: initializes PWM channel, sets initial frequency and duty cycle.

Parameters

channel	PWM channel number (0 or 1).
frequency_hz	Initial frequency in Hz. Default is 1000 Hz.
duty_percent	Initial duty cycle (range: 0.0 ~ 1.0).
chip	PWM chip number. Default is 2 for Raspberry Pi 5.

Definition at line 37 of file bsp_pwm.hpp.

      : channel_(channel), period_ns_(static_cast<int>(1e9 / frequency_hz)) {
    chip_path_ = "/sys/class/pwm/pwmchip" + std::to_string(chip);
    pwm_path_ = chip_path_ + "/pwm" + std::to_string(channel);
 
    // Export the PWM channel if it has not been exported yet.
    if (access(pwm_path_.c_str(), F_OK) != 0) {
      FILE* fp = fopen((chip_path_ + "/export").c_str(), "w");
      if (fp) {
        (void)(fprintf(fp, "%d", channel));
        (void)(fclose(fp));
        usleep(100000);  // Allow sysfs to initialize.
      }
    }
 
    WriteSysfs(pwm_path_ + "/period", period_ns_);
    SetDutyCycle(duty_percent);
    Enable();
 
    // Launch background thread to play notes asynchronously.
    note_thread_ = std::thread([this]() {
      while (true) {
        note_sem_.acquire();
        float midi = static_cast<float>(note_) +
                     (static_cast<float>(octave_) + 1.0f) * 12.0f;
        float freq = 440.0f * std::pow(2.0f, (midi - 69.0f) / 12.0f);
        Beep(static_cast<uint32_t>(freq), duration_ms_);
      }
    });
  }

◆ ~PWM()

PWM::~PWM ( )

inline

Destructor: disables PWM output.

Definition at line 72 of file bsp_pwm.hpp.

72{ Disable(); }

PWM::Disable

void Disable()

Disable the PWM output signal.

Definition bsp_pwm.hpp:100

Member Function Documentation

◆ Beep()

void PWM::Beep	(	uint32_t	freq,
		uint32_t	duration_ms
	)

inline

Output a beep with specific frequency and duration.

Parameters

freq	Frequency in Hz.
duration_ms	Duration in milliseconds.

Definition at line 107 of file bsp_pwm.hpp.

                                                 {
    SetFrequency(freq);
    SetDutyCycle(0.5f);
    Enable();
    usleep(duration_ms * 1000);
    Disable();
  }

◆ Disable()

void PWM::Disable ( )

inline

Disable the PWM output signal.

Definition at line 100 of file bsp_pwm.hpp.

100{ WriteSysfs(pwm_path_ + "/enable", 0); }

◆ Enable()

void PWM::Enable ( )

inline

Enable the PWM output signal.

Definition at line 95 of file bsp_pwm.hpp.

95{ WriteSysfs(pwm_path_ + "/enable", 1); }

◆ PlayNote()

void PWM::PlayNote	(	NoteName	note,
		uint32_t	octave,
		uint32_t	duration_ms
	)

inline

Play a musical note based on note name and octave.

Parameters

note	Note (C, D, E, etc.).
octave	Octave number (e.g., 4 for A4 = 440 Hz).
duration_ms	Duration of the note in milliseconds.

Definition at line 121 of file bsp_pwm.hpp.

                                                                      {
    note_ = note;
    octave_ = octave;
    duration_ms_ = duration_ms;
    note_sem_.release();
  }

◆ SetAlarmConfig()

void PWM::SetAlarmConfig	(	uint32_t	freq,
		uint32_t	duration_ms,
		uint32_t	delay_ms
	)

inline

Set configuration parameters for alarm beep.

Parameters

freq	Alarm frequency in Hz.
duration_ms	Duration of tone in milliseconds.
delay_ms	Delay after the tone in milliseconds.

Definition at line 134 of file bsp_pwm.hpp.

                                                                              {
    alarm_freq_ = freq;
    alarm_duration_ = duration_ms;
    alarm_delay_ = delay_ms;
  }

◆ SetDutyCycle()

void PWM::SetDutyCycle ( float percent )

inline

Set the duty cycle of PWM output.

Parameters

percent Duty cycle as a float between 0.0 and 1.0.

Definition at line 87 of file bsp_pwm.hpp.

                                   {
    int duty_ns = static_cast<int>(percent * static_cast<float>(period_ns_));
    WriteSysfs(pwm_path_ + "/duty_cycle", duty_ns);
  }

◆ SetFrequency()

void PWM::SetFrequency ( uint32_t hz )

inline

Set the output frequency of PWM.

Parameters

hz	Desired frequency in Hz.

Definition at line 78 of file bsp_pwm.hpp.

                                 {
    period_ns_ = static_cast<int>(1e9 / hz);
    WriteSysfs(pwm_path_ + "/period", period_ns_);
  }

◆ TriggerAlarm()

void PWM::TriggerAlarm ( )

inline

Trigger an alarm sound followed by a delay.

Definition at line 143 of file bsp_pwm.hpp.

                      {
    Beep(alarm_freq_, alarm_duration_);
    usleep(alarm_delay_ * 1000);
  }

◆ WriteSysfs()

int PWM::WriteSysfs	(	const std::string &	path,
		int	value
	)		const

inlineprivate

Write an integer value to a sysfs file.

Parameters

path	Full path to the sysfs file.
value	Integer value to write.

Returns: Write result (number of characters written) or -1 on error.

Definition at line 170 of file bsp_pwm.hpp.

                                                         {
    FILE* fp = fopen(path.c_str(), "w");
    if (!fp) {
      return -1;
    }
    int result = fprintf(fp, "%d", value);
    (void)(fclose(fp));
    return result;
  }

Field Documentation

◆ alarm_delay_

uint32_t PWM::alarm_delay_ = 300

private

Default alarm delay in ms.

Definition at line 156 of file bsp_pwm.hpp.

◆ alarm_duration_

uint32_t PWM::alarm_duration_ = 300

private

Default alarm duration in ms.

Definition at line 155 of file bsp_pwm.hpp.

◆ alarm_freq_

uint32_t PWM::alarm_freq_ = 1500

private

Default alarm frequency in Hz.

Definition at line 154 of file bsp_pwm.hpp.

◆ channel_

int PWM::channel_

private

PWM channel number.

Definition at line 152 of file bsp_pwm.hpp.

◆ chip_path_

std::string PWM::chip_path_

private

Sysfs path to the PWM chip.

Definition at line 149 of file bsp_pwm.hpp.

◆ duration_ms_

uint32_t PWM::duration_ms_

private

Duration of note in ms.

Definition at line 161 of file bsp_pwm.hpp.

◆ note_

NoteName PWM::note_

private

Current note name.

Definition at line 159 of file bsp_pwm.hpp.

◆ note_sem_

std::binary_semaphore PWM::note_sem_ {0}

private

Semaphore to trigger note play.

Definition at line 162 of file bsp_pwm.hpp.

162{0};

◆ note_thread_

std::thread PWM::note_thread_

private

Background thread for playing notes.

Definition at line 158 of file bsp_pwm.hpp.

◆ octave_

uint32_t PWM::octave_

private

Current octave.

Definition at line 160 of file bsp_pwm.hpp.

◆ period_ns_

int PWM::period_ns_

private

PWM period in nanoseconds.

Definition at line 151 of file bsp_pwm.hpp.

◆ pwm_path_

std::string PWM::pwm_path_

private

Sysfs path to the PWM channel.

Definition at line 150 of file bsp_pwm.hpp.

The documentation for this class was generated from the following file:

src/bsp/bsp_pwm.hpp

Public Types

Public Member Functions

Private Member Functions

Private Attributes

Detailed Description

Member Enumeration Documentation

◆ NoteName

Constructor & Destructor Documentation

◆ PWM()

◆ ~PWM()

Member Function Documentation

◆ Beep()

◆ Disable()

◆ Enable()

◆ PlayNote()

◆ SetAlarmConfig()

◆ SetDutyCycle()

◆ SetFrequency()

◆ TriggerAlarm()

◆ WriteSysfs()

Field Documentation

◆ alarm_delay_

◆ alarm_duration_

◆ alarm_freq_

◆ channel_

◆ chip_path_

◆ duration_ms_

◆ note_

◆ note_sem_

◆ note_thread_

◆ octave_

◆ period_ns_

◆ pwm_path_