machine/esp32: add PWM support using LEDC peripheral #5186
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Add PWM support for ESP32 using the LEDC (LED Control) peripheral. Features: - 4 high-speed timers (PWM0-PWM3) with glitch-free duty updates - Up to 8 channels shared across timers - Configurable duty resolution (1-20 bits) - Flexible frequency control via period setting - Any GPIO can be used via GPIO matrix routing The implementation follows the standard TinyGo PWM interface with Configure, Channel, Set, SetPeriod, Top, and SetInverting methods. Co-authored-by: Ona <no-reply@ona.com>
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Fix several issues with the LEDC PWM implementation: 1. Timer reset: The reset bit must be set then cleared (not just set) 2. CONF1 register: For non-fading operation, duty_cycle and duty_num must be set to 1, and duty_inc must be enabled 3. Duty update: Properly configure CONF1 when updating duty values These fixes align with the ESP-IDF LEDC driver implementation. Co-authored-by: Ona <no-reply@ona.com>
The LEDC clock divider register uses 8 fractional bits, meaning the register value is actual_divider * 256. The previous implementation was setting the divider directly without accounting for this, resulting in a divider that was 256x smaller than intended. Also added: - Set LEDC.CONF.APB_CLK_SEL = 1 to select APB clock source - Updated Period() calculation to account for fractional bits Co-authored-by: Ona <no-reply@ona.com>
- Always write full CONF1 register value when updating duty - Re-enable sig_out_en on each duty update (matching ESP-IDF behavior) This should improve the smoothness of duty cycle transitions. Co-authored-by: Ona <no-reply@ona.com>
The duty_resolution register stores the bit width directly, not bit width - 1. Setting resolution-1 caused the timer counter to wrap at half the expected value, resulting in duty cycle glitches when the duty value exceeded the actual counter range. For example, with 20-bit resolution intended: - Before: register = 19, counter wraps at 524287 - After: register = 20, counter wraps at 1048575 This fixes the 'reset in the middle' behavior during fades. Co-authored-by: Ona <no-reply@ona.com>
Improvements: - Fix SetPeriod using resolution-1 instead of resolution - Refactor channel tracking to properly associate channels with timers - Add pwmChannelInfo struct to track pin, timer, and usage state - Prevent same pin from being used on different timers - Add ReleaseChannel() method to free channels - Add Get() method to read current duty value - Fix SetInverting to use GPIO matrix inversion (bit 9) - SetPeriod now only scales channels bound to this timer - Remove unused constants, add named constants for defaults - Add bounds checking in Period() for zero values Co-authored-by: Ona <no-reply@ona.com>
Additional improvements: - Add errPWMPeriodTooShort error for periods that are too short - Add pwmChannelCount constant and use it consistently - Add gpioMatrixInvertBit constant for clarity - Use dividerFracBits constant in calculations instead of magic 256 - Add isValidChannel() helper for centralized validation - Add IsConnected() method to check if channel is in use - Add SetCounter() method for timer synchronization (API compatibility) - Handle unconfigured timer in Set() by using default resolution - Improve Enable() documentation - Remove unused chanIdleLvMask constant Co-authored-by: Ona <no-reply@ona.com>
Additional improvements: - Add pwmTimerCount constant and use it for pwmStates array - Use pwmChannelCount constant for pwmChannels array declaration - Add IsEnabled() method to check if timer is running - Add Frequency() method to get current PWM frequency in Hz - Add Resolution() method to get current duty resolution in bits - Add GetPin() method to get pin assigned to a channel - Rename SetCounter() to ResetCounter() (ESP32 only supports reset to 0) - Fix Period() to use dividerFracBits constant instead of magic 256 - Remove misleading 'Idle level low' comment in Channel() Co-authored-by: Ona <no-reply@ona.com>
Final improvements: - Add apbClockMHz constant (80) instead of hardcoded values - Add timerRegisterStride and channelRegisterStride constants - Add SetFrequency() method for convenience - Add ChannelCount() method to query available channels - Optimize Channel() to use single-pass loop instead of three loops - Add error documentation to Channel() function comment - Simplify register access helper comments Co-authored-by: Ona <no-reply@ona.com>
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Summary
Add PWM support for ESP32 using the LEDC (LED Control) peripheral. We are not including Motor control PWM because it would probably require a different API and the current existing LEDC should work well for leds and basic motors and servos.
Features
PWM0-PWM3) with glitch-free duty updatesImplementation Details
The implementation uses the ESP32's LEDC peripheral which is designed for LED dimming but works well for general PWM applications. Key characteristics:
API
Follows the standard TinyGo PWM interface:
Files Changed
src/machine/machine_esp32_pwm.go- Main PWM implementationsrc/examples/pwm/esp32.go- Example configuration for ESP32 boardsTesting
gofmt