Audio output to PWM pins for the ESP32. The ESP32 supports up to 16 channels. More...
#include <PWMComplementaryDriverESP32.h>
Public Member Functions | |
| PWMConfig & | audioInfo () |
| virtual int | availableForWrite () |
| bool | begin (PWMConfig cfg) |
| virtual PWMConfig | defaultConfig () |
| virtual int | effectiveOutputSampleRate () |
| Provides the effective sample rate. | |
| virtual void | end () |
| uint32_t | framesPerSecond () |
| bool | isTimerStarted () |
| virtual void | pwmWrite (int channel, int value) |
| void | setBuffer (BaseBuffer< uint8_t > *buffer) |
| virtual void | setupPWM () |
| Setup complementary MCPWM. | |
| virtual void | setupTimer () |
| Setup ESP32 timer with callback. | |
| virtual void | startTimer () |
| uint32_t | underflowsPerSecond () |
| void | updateStatistics () |
| virtual size_t | write (const uint8_t *data, size_t len) |
Protected Member Functions | |
| virtual int | decimation () |
| Decimation factor to reduce the sample rate. | |
| void | deleteBuffer () |
| float | frequency (int resolution) |
| determiens the PWM frequency based on the requested resolution | |
| virtual bool | isDecimateActive () |
| virtual int | maxChannels () |
| virtual int | maxOutputValue () |
| provides the max value for the configured resulution | |
| virtual int | maxSampleRate () |
| Provides the max working sample rate. | |
| int | maxUnsignedValue (int resolution) |
| provides the max value for the indicated resulution | |
| virtual int | nextValue () |
| determines the next scaled value | |
| void | playNextFrame () |
| writes the next frame to the output pins | |
Static Protected Member Functions | |
| static void | pwm_callback (void *ptr) |
| timer callback: write the next frame to the pins | |
Protected Attributes | |
| AudioInfo | actual_info |
| uint32_t | actual_timer_frequency = 0 |
| PWMConfig | audio_config |
| BaseBuffer< uint8_t > * | buffer = nullptr |
| Decimate | decimate |
| int | decimation_factor = 0 |
| uint32_t | frame_count = 0 |
| uint32_t | frame_size = 0 |
| uint32_t | frames_per_second = 0 |
| bool | is_blocking_write = true |
| bool | is_timer_started = false |
| Vector< PinInfoESP32Compl > | pins |
| uint32_t | time_1_sec |
| TimerAlarmRepeating | timer |
| uint32_t | underflow_count = 0 |
| uint32_t | underflow_per_second = 0 |
Detailed Description
Audio output to PWM pins for the ESP32. The ESP32 supports up to 16 channels.
- Copyright
- GPLv3
Complementary (half‑bridge) PWM audio driver for ESP32 using the legacy MCPWM driver API.
This driver produces audio by modulating one or more complementary PWM pairs (high / low outputs) using the ESP32 MCPWM peripheral. Each audio channel occupies one MCPWM timer (up to 3 timers per MCPWM unit, and 2 units → maximum of 6 complementary channels). For every channel two GPIOs are driven 180° out of phase. Optional hardware dead time can be inserted to protect external half‑bridge power stages.
The duty cycle is derived from the (optionally decimated) audio samples in the base class buffer. The effective output sample rate equals the rate at which new duty values are pushed to the MCPWM hardware (timer interrupt / alarm frequency) and may differ from the nominal input sample rate due to decimation (see DriverPWMBase).
Resolution & PWM Frequency: The requested bit resolution (e.g. 8–11 bits) determines the PWM carrier frequency using empirically chosen values (see frequency()). If PWMConfig::pwm_frequency is left as 0 the driver derives it from the resolution. Otherwise the provided frequency is used.
Dead Time: If PWMConfig::dead_time_us > 0 the driver configures hardware complementary mode with symmetric dead time (rising & falling) in ticks computed from the APB clock (assumed 80 MHz). For very large dead time requests relative to the PWM period the value is limited to maintain a usable duty range. Without dead time the driver emulates complementary operation by inverting the B duty in software (B = 100% - A).
Pin Assignment: Provide either 2 * channels GPIO values (high0, low0, high1, low1, ...). If only one pin per channel is supplied the low pin is assumed to be high+1.
Limitations:
- Uses the legacy MCPWM API (driver/mcpwm.h). ESP-IDF v5+ introduces a new prelude API which is not covered here.
- Maximum 6 complementary channels (2 units * 3 timers).
- Dead time calculation assumes 80 MHz APB clock.
- No dynamic reconfiguration of frequency / dead time while running; call end() and begin() again to change.
Thread Safety: Access from a single task context; ISR only invokes playNextFrame().
Member Function Documentation
◆ decimation()
|
inlineprotectedvirtualinherited |
Decimation factor to reduce the sample rate.
Reimplemented in PWMDriverRenesas.
◆ end()
|
inlinevirtual |
Reimplemented from DriverPWMBase.
◆ isDecimateActive()
|
inlineprotectedvirtualinherited |
The requested sampling rate is too hight: we only process half of the samples so we can half the sampling rate
◆ maxChannels()
|
inlineprotectedvirtual |
Implements DriverPWMBase.
◆ maxOutputValue()
|
inlineprotectedvirtual |
provides the max value for the configured resulution
Implements DriverPWMBase.
◆ maxSampleRate()
|
inlineprotectedvirtualinherited |
Provides the max working sample rate.
Reimplemented in PWMDriverRenesas.
◆ pwmWrite()
|
inlinevirtual |
write a pwm value to the indicated channel. The max value depends on the resolution
Implements DriverPWMBase.
◆ setBuffer()
|
inlineinherited |
You can assign your own custom buffer impelementation: must be allocated on the heap and will be cleaned up by this class
◆ setupPWM()
|
inlinevirtual |
Setup complementary MCPWM.
Implements DriverPWMBase.
◆ setupTimer()
|
inlinevirtual |
Setup ESP32 timer with callback.
Implements DriverPWMBase.
◆ startTimer()
|
inlinevirtual |
when we get the first write -> we activate the timer to start with the output of data
Implements DriverPWMBase.
The documentation for this class was generated from the following file:
- src/AudioTools/CoreAudio/AudioPWM/PWMComplementaryDriverESP32.h
