The LED control (LEDC) peripheral is primarily designed to control the intensity of LEDs, although it can also be used to generate PWM signals for other purposes. It has 8 channels which can generate independent waveforms that can be used, for example, to drive RGB LED devices.
LEDC channels are divided into two groups of 8 channels each. One group of LEDC channels operates in high speed mode. This mode is implemented in hardware and offers automatic and glitch-free changing of the PWM duty cycle. The other group of channels operate in low speed mode, the PWM duty cycle must be changed by the driver in software. Each group of channels is also able to use different clock sources.
The PWM controller can automatically increase or decrease the duty cycle gradually, allowing for fades without any processor interference.
Functionality OverviewïSetting up a channel of the LEDC in either high or low speed mode is done in three steps:
Timer Configuration by specifying the PWM signal's frequency and duty cycle resolution.
Channel Configuration by associating it with the timer and GPIO to output the PWM signal.
Change PWM Signal that drives the output in order to change LED's intensity. This can be done under the full control of software or with hardware fading functions.
As an optional step, it is also possible to set up an interrupt on fade end.
Key Settings of LED PWM Controller's APIï
Note
For an initial setup, it is recommended to configure for the timers first (by calling ledc_timer_config()), and then for the channels (by calling ledc_channel_config()). This ensures the PWM frequency is at the desired value since the appearance of the PWM signal from the IO pad.
Setting the timer is done by calling the function ledc_timer_config() and passing the data structure ledc_timer_config_t that contains the following configuration settings:
Speed mode ledc_mode_t
Timer number ledc_timer_t
PWM signal frequency in Hz
Resolution of PWM duty
Source clock ledc_clk_cfg_t
The frequency and the duty resolution are interdependent. The higher the PWM frequency, the lower the duty resolution which is available, and vice versa. This relationship might be important if you are planning to use this API for purposes other than changing the intensity of LEDs. For more details, see Section Supported Range of Frequency and Duty Resolutions.
The source clock can also limit the PWM frequency. The higher the source clock frequency, the higher the maximum PWM frequency can be configured.
Characteristics of ESP32 LEDC source clocksïClock name
Clock freq
Speed mode
Clock capabilities
APB_CLK
80 MHz
High / Low
/
REF_TICK
1 MHz
High / Low
Dynamic Frequency Scaling compatible
RC_FAST_CLK
~ 8 MHz
Low
Dynamic Frequency Scaling compatible, Light-sleep compatible
Note
On ESP32, if RC_FAST_CLK is chosen as the LEDC clock source, an internal calibration will be performed to get the exact frequency of the clock. This ensures the accuracy of output PWM signal frequency.
The LEDC driver offers a helper function ledc_find_suitable_duty_resolution() to find the maximum possible resolution for the timer, given the source clock frequency and the desired PWM signal frequency.
When a timer is no longer needed by any channel, it can be deconfigured by calling the same function ledc_timer_config(). The configuration structure ledc_timer_config_t passes in should be:
ledc_timer_config_t::speed_mode The speed mode of the timer which wants to be deconfigured belongs to (ledc_mode_t)
ledc_timer_config_t::timer_num The ID of the timers which wants to be deconfigured (ledc_timer_t)
ledc_timer_config_t::deconfigure Set this to true so that the timer specified can be deconfigured
When the timer is set up, configure the desired channel (one out of ledc_channel_t). This is done by calling the function ledc_channel_config().
Similar to the timer configuration, the channel setup function should be passed a structure ledc_channel_config_t that contains the channel's configuration parameters.
At this point, the channel should start operating and generating the PWM signal on the selected GPIO, as configured in ledc_channel_config_t, with the frequency specified in the timer settings and the given duty cycle. The channel operation (signal generation) can be suspended at any time by calling the function ledc_stop().
Once the channel starts operating and generating the PWM signal with the constant duty cycle and frequency, there are a couple of ways to change this signal. When driving LEDs, primarily the duty cycle is changed to vary the light intensity.
The following two sections describe how to change the duty cycle using software and hardware fading. If required, the signal's frequency can also be changed; it is covered in Section Change PWM Frequency.
Change PWM Duty Cycle Using SoftwareïTo set the duty cycle, use the dedicated function ledc_set_duty(). After that, call ledc_update_duty() to activate the changes. To check the currently set value, use the corresponding _get_ function ledc_get_duty().
Another way to set the duty cycle, as well as some other channel parameters, is by calling ledc_channel_config() covered in Section Channel Configuration.
The range of the duty cycle values passed to functions depends on selected duty_resolution and should be from 0 to (2 ** duty_resolution). For example, if the selected duty resolution is 10, then the duty cycle values can range from 0 to 1024. This provides the resolution of ~ 0.1%.
Warning
On ESP32, when channel's binded timer selects its maximum duty resolution, the duty cycle value cannot be set to (2 ** duty_resolution). Otherwise, the internal duty counter in the hardware will overflow and be messed up.
The LEDC hardware provides the means to gradually transition from one duty cycle value to another. To use this functionality, enable fading with ledc_fade_func_install() and then configure it by calling one of the available fading functions:
Start fading with ledc_fade_start(). A fade can be operated in blocking or non-blocking mode, please check ledc_fade_mode_t for the difference between the two available fade modes. Note that with either fade mode, the next fade or fixed-duty update will not take effect until the last fade finishes. Due to hardware limitations, there is no way to stop a fade before it reaches its target duty.
To get a notification about the completion of a fade operation, a fade end callback function can be registered for each channel by calling ledc_cb_register() after the fade service being installed. The fade end callback prototype is defined in ledc_cb_t, where you should return a boolean value from the callback function, indicating whether a high priority task is woken up by this callback function. It is worth mentioning, the callback and the function invoked by itself should be placed in IRAM, as the interrupt service routine is in IRAM. ledc_cb_register() will print a warning message if it finds the addresses of callback and user context are incorrect.
If not required anymore, fading and an associated interrupt can be disabled with ledc_fade_func_uninstall().
The LEDC API provides several ways to change the PWM frequency "on the fly":
More Control Over PWMï
There are several individual timer-specific functions that can be used to change PWM output:
The first function is called "behind the scenes" by ledc_timer_config() to provide a startup of a timer after it is configured.
LEDC driver does not utilize power management lock to prevent the system from going into Light-sleep. Instead, the LEDC peripheral power domain state and the PWM signal output behavior during sleep can be chosen by configuring ledc_channel_config_t::sleep_mode. The default mode is LEDC_SLEEP_MODE_NO_ALIVE_NO_PD, which stands for no signal output and LEDC power domain will not be powered down during sleep.
If signal output needs to be maintained in Light-sleep, then select LEDC_SLEEP_MODE_KEEP_ALIVE. As long as the binded LEDC timer clock source is Light-sleep compatible, the PWM signal can continue its output even the system enters Light-sleep. The cost is a higher power consumption in sleep, since the clock source and the power domain where LEDC belongs to cannot be powered down. Note that, if there is an unfinished fade before entering sleep, the fade can also continue during sleep, but the target duty might not be reached exactly. It will adjust to the target duty after wake-up.
High speed mode enables a glitch-free changeover of timer settings. This means that if the timer settings are modified, the changes will be applied automatically on the next overflow interrupt of the timer. In contrast, when updating the low-speed timer, the change of settings should be explicitly triggered by software. The LEDC driver handles it in the background, e.g., when ledc_timer_config() is called.
For additional details regarding speed modes, see ESP32 Technical Reference Manual > LED PWM Controller (LEDC) [PDF].
Supported Range of Frequency and Duty ResolutionsïThe LED PWM Controller is designed primarily to drive LEDs. It provides a large flexibility of PWM duty cycle settings. For instance, the PWM frequency of 5 kHz can have the maximum duty resolution of 13 bits. This means that the duty can be set anywhere from 0 to 100% with a resolution of ~ 0.012% (2 ** 13 = 8192 discrete levels of the LED intensity). Note, however, that these parameters depend on the clock signal clocking the LED PWM Controller timer which in turn clocks the channel (see timer configuration and the ESP32 Technical Reference Manual > LED PWM Controller (LEDC) [PDF]).
The LEDC can be used for generating signals at much higher frequencies that are sufficient enough to clock other devices, e.g., a digital camera module. In this case, the maximum available frequency is 40 MHz with duty resolution of 1 bit. This means that the duty cycle is fixed at 50% and cannot be adjusted.
The LEDC API is designed to report an error when trying to set a frequency and a duty resolution that exceed the range of LEDC's hardware. For example, an attempt to set the frequency to 20 MHz and the duty resolution to 3 bits results in the following error reported on a serial monitor:
E (196) ledc: requested frequency and duty resolution cannot be achieved, try reducing freq_hz or duty_resolution. div_param=128
In such a situation, either the duty resolution or the frequency must be reduced. For example, setting the duty resolution to 2 resolves this issue and makes it possible to set the duty cycle at 25% steps, i.e., at 25%, 50% or 75%.
The LEDC driver also captures and reports attempts to configure frequency/duty resolution combinations that are below the supported minimum, e.g.,:
E (196) ledc: requested frequency and duty resolution cannot be achieved, try increasing freq_hz or duty_resolution. div_param=128000000
The duty resolution is normally set using ledc_timer_bit_t. This enumeration covers the range from 10 to 15 bits. If a smaller duty resolution is required (from 10 down to 1), enter the equivalent numeric values directly.
peripherals/ledc/ledc_basic demonstrates how to use the LEDC to generate a PWM signal in LOW SPEED mode.
peripherals/ledc/ledc_fade demonstrates how to control the intensity of LEDs using the LEDC fade functionality.
LEDC channel configuration Configure LEDC channel with the given channel/output gpio_num/interrupt/source timer/frequency(Hz)/LEDC duty.
ledc_conf -- Pointer of LEDC channel configure struct
ESP_OK Success
ESP_ERR_INVALID_ARG Parameter error
Helper function to find the maximum possible duty resolution in bits for ledc_timer_config()
src_clk_freq -- LEDC timer source clock frequency (Hz) (See doxygen comments of ledc_clk_cfg_t or get from esp_clk_tree_src_get_freq_hz)
timer_freq -- Desired LEDC timer frequency (Hz)
0 The timer frequency cannot be achieved
Others The largest duty resolution value to be set
LEDC timer configuration Configure LEDC timer with the given source timer/frequency(Hz)/duty_resolution.
timer_conf -- Pointer of LEDC timer configure struct
ESP_OK Success
ESP_ERR_INVALID_ARG Parameter error
ESP_FAIL Can not find a proper pre-divider number base on the given frequency and the current duty_resolution.
ESP_ERR_INVALID_STATE Timer cannot be de-configured because timer is not configured or is not paused
LEDC update channel parameters.
Note
Call this function to activate the LEDC updated parameters. After ledc_set_duty, we need to call this function to update the settings. And the new LEDC parameters don't take effect until the next PWM cycle.
Note
ledc_set_duty, ledc_set_duty_with_hpoint and ledc_update_duty are not thread-safe, do not call these functions to control one LEDC channel in different tasks at the same time. A thread-safe version of API is ledc_set_duty_and_update
Note
If CONFIG_LEDC_CTRL_FUNC_IN_IRAM is enabled, this function will be placed in the IRAM by linker, makes it possible to execute even when the Cache is disabled.
Note
This function is allowed to run within ISR context.
speed_mode -- Select the LEDC channel group with specified speed mode. Note that not all targets support high speed mode.
channel -- LEDC channel (0 - LEDC_CHANNEL_MAX-1), select from ledc_channel_t
ESP_OK Success
ESP_ERR_INVALID_ARG Parameter error
Set LEDC output gpio.
Note
This function only routes the LEDC signal to GPIO through matrix, other LEDC resources initialization are not involved. Please use ledc_channel_config() instead to fully configure a LEDC channel.
gpio_num -- The LEDC output gpio
speed_mode -- Select the LEDC channel group with specified speed mode. Note that not all targets support high speed mode.
channel -- LEDC channel (0 - LEDC_CHANNEL_MAX-1), select from ledc_channel_t
ESP_OK Success
ESP_ERR_INVALID_ARG Parameter error
LEDC stop. Disable LEDC output, and set idle level.
Note
If CONFIG_LEDC_CTRL_FUNC_IN_IRAM is enabled, this function will be placed in the IRAM by linker, makes it possible to execute even when the Cache is disabled.
Note
This function is allowed to run within ISR context.
speed_mode -- Select the LEDC channel group with specified speed mode. Note that not all targets support high speed mode.
channel -- LEDC channel (0 - LEDC_CHANNEL_MAX-1), select from ledc_channel_t
idle_level -- Set output idle level after LEDC stops.
ESP_OK Success
ESP_ERR_INVALID_ARG Parameter error
LEDC set channel frequency (Hz)
speed_mode -- Select the LEDC channel group with specified speed mode. Note that not all targets support high speed mode.
timer_num -- LEDC timer index (0-3), select from ledc_timer_t
freq_hz -- Set the LEDC frequency
ESP_OK Success
ESP_ERR_INVALID_ARG Parameter error
ESP_FAIL Can not find a proper pre-divider number base on the given frequency and the current duty_resolution.
LEDC get channel frequency (Hz)
speed_mode -- Select the LEDC channel group with specified speed mode. Note that not all targets support high speed mode.
timer_num -- LEDC timer index (0-3), select from ledc_timer_t
0 error
Others Current LEDC frequency
LEDC set duty and hpoint value Only after calling ledc_update_duty will the duty update.
Note
ledc_set_duty, ledc_set_duty_with_hpoint and ledc_update_duty are not thread-safe, do not call these functions to control one LEDC channel in different tasks at the same time. A thread-safe version of API is ledc_set_duty_and_update
Note
For ESP32, hardware does not support any duty change while a fade operation is running in progress on that channel. Other duty operations will have to wait until the fade operation has finished.
speed_mode -- Select the LEDC channel group with specified speed mode. Note that not all targets support high speed mode.
channel -- LEDC channel (0 - LEDC_CHANNEL_MAX-1), select from ledc_channel_t
duty -- Set the LEDC duty, the range of duty setting is [0, (2**duty_resolution)]
hpoint -- Set the LEDC hpoint value, the range is [0, (2**duty_resolution)-1]
ESP_OK Success
ESP_ERR_INVALID_ARG Parameter error
LEDC get hpoint value, the counter value when the output is set high level.
speed_mode -- Select the LEDC channel group with specified speed mode. Note that not all targets support high speed mode.
channel -- LEDC channel (0 - LEDC_CHANNEL_MAX-1), select from ledc_channel_t
LEDC_ERR_VAL if parameter error
Others Current hpoint value of LEDC channel
LEDC set duty This function do not change the hpoint value of this channel. if needed, please call ledc_set_duty_with_hpoint. only after calling ledc_update_duty will the duty update.
Note
ledc_set_duty, ledc_set_duty_with_hpoint and ledc_update_duty are not thread-safe, do not call these functions to control one LEDC channel in different tasks at the same time. A thread-safe version of API is ledc_set_duty_and_update.
Note
For ESP32, hardware does not support any duty change while a fade operation is running in progress on that channel. Other duty operations will have to wait until the fade operation has finished.
speed_mode -- Select the LEDC channel group with specified speed mode. Note that not all targets support high speed mode.
channel -- LEDC channel (0 - LEDC_CHANNEL_MAX-1), select from ledc_channel_t
duty -- Set the LEDC duty, the range of duty setting is [0, (2**duty_resolution)]
ESP_OK Success
ESP_ERR_INVALID_ARG Parameter error
LEDC get duty This function returns the duty at the present PWM cycle. You shouldn't expect the function to return the new duty in the same cycle of calling ledc_update_duty, because duty update doesn't take effect until the next cycle.
speed_mode -- Select the LEDC channel group with specified speed mode. Note that not all targets support high speed mode.
channel -- LEDC channel (0 - LEDC_CHANNEL_MAX-1), select from ledc_channel_t
LEDC_ERR_DUTY if parameter error
Others Current LEDC duty
LEDC set gradient Set LEDC gradient, After the function calls the ledc_update_duty function, the function can take effect.
Note
For ESP32, hardware does not support any duty change while a fade operation is running in progress on that channel. Other duty operations will have to wait until the fade operation has finished.
speed_mode -- Select the LEDC channel group with specified speed mode. Note that not all targets support high speed mode.
channel -- LEDC channel (0 - LEDC_CHANNEL_MAX-1), select from ledc_channel_t
duty -- Set the start of the gradient duty, the range of duty setting is [0, (2**duty_resolution)]
fade_direction -- Set the direction of the gradient
step_num -- Set the number of the gradient
duty_cycle_num -- Set how many LEDC tick each time the gradient lasts
duty_scale -- Set gradient change amplitude
ESP_OK Success
ESP_ERR_INVALID_ARG Parameter error
Register LEDC interrupt handler, the handler is an ISR. The handler will be attached to the same CPU core that this function is running on.
fn -- Interrupt handler function.
arg -- User-supplied argument passed to the handler function.
intr_alloc_flags -- Flags used to allocate the interrupt. One or multiple (ORred) ESP_INTR_FLAG_* values. See esp_intr_alloc.h for more info.
handle -- Pointer to return handle. If non-NULL, a handle for the interrupt will be returned here.
ESP_OK Success
ESP_ERR_INVALID_ARG Parameter error
ESP_ERR_NOT_FOUND Failed to find available interrupt source
Reset LEDC timer.
speed_mode -- Select the LEDC channel group with specified speed mode. Note that not all targets support high speed mode.
timer_sel -- LEDC timer index (0-3), select from ledc_timer_t
ESP_ERR_INVALID_ARG Parameter error
ESP_OK Success
Pause LEDC timer counter.
speed_mode -- Select the LEDC channel group with specified speed mode. Note that not all targets support high speed mode.
timer_sel -- LEDC timer index (0-3), select from ledc_timer_t
ESP_ERR_INVALID_ARG Parameter error
ESP_OK Success
Resume LEDC timer.
speed_mode -- Select the LEDC channel group with specified speed mode. Note that not all targets support high speed mode.
timer_sel -- LEDC timer index (0-3), select from ledc_timer_t
ESP_ERR_INVALID_ARG Parameter error
ESP_OK Success
Bind LEDC channel with the selected timer.
speed_mode -- Select the LEDC channel group with specified speed mode. Note that not all targets support high speed mode.
channel -- LEDC channel index (0 - LEDC_CHANNEL_MAX-1), select from ledc_channel_t
timer_sel -- LEDC timer index (0-3), select from ledc_timer_t
ESP_ERR_INVALID_ARG Parameter error
ESP_OK Success
Set LEDC fade function.
Note
Call ledc_fade_func_install() once before calling this function. Call ledc_fade_start() after this to start fading.
Note
ledc_set_fade_with_step, ledc_set_fade_with_time and ledc_fade_start are not thread-safe, do not call these functions to control one LEDC channel in different tasks at the same time. A thread-safe version of API is ledc_set_fade_step_and_start
Note
For ESP32, hardware does not support any duty change while a fade operation is running in progress on that channel. Other duty operations will have to wait until the fade operation has finished.
speed_mode -- Select the LEDC channel group with specified speed mode. Note that not all targets support high speed mode.
channel -- LEDC channel index (0 - LEDC_CHANNEL_MAX-1), select from ledc_channel_t
target_duty -- Target duty of fading [0, (2**duty_resolution)]
scale -- Controls the increase or decrease step scale.
cycle_num -- increase or decrease the duty every cycle_num cycles
ESP_OK Success
ESP_ERR_INVALID_ARG Parameter error
ESP_ERR_INVALID_STATE Channel not initialized
ESP_FAIL Fade function init error
Set LEDC fade function, with a limited time.
Note
Call ledc_fade_func_install() once before calling this function. Call ledc_fade_start() after this to start fading.
Note
ledc_set_fade_with_step, ledc_set_fade_with_time and ledc_fade_start are not thread-safe, do not call these functions to control one LEDC channel in different tasks at the same time. A thread-safe version of API is ledc_set_fade_step_and_start
Note
For ESP32, hardware does not support any duty change while a fade operation is running in progress on that channel. Other duty operations will have to wait until the fade operation has finished.
speed_mode -- Select the LEDC channel group with specified speed mode. Note that not all targets support high speed mode.
channel -- LEDC channel index (0 - LEDC_CHANNEL_MAX-1), select from ledc_channel_t
target_duty -- Target duty of fading [0, (2**duty_resolution)]
desired_fade_time_ms -- The intended time of the fading ( ms ). Note that the actual time it takes to complete the fade could vary by a factor of up to 2x shorter or longer than the expected time due to internal rounding errors in calculations. Specifically:
The total number of cycles (total_cycle_num = desired_fade_time_ms * freq / 1000)
The difference in duty cycle (duty_delta = |target_duty - current_duty|) The fade may complete faster than expected if total_cycle_num larger than duty_delta. Conversely, it may take longer than expected if total_cycle_num is less than duty_delta. The closer the ratio of total_cycle_num/duty_delta (or its inverse) is to a whole number (the floor value), the more accurately the actual fade duration will match the intended time. If an exact fade time is expected, please consider to split the entire fade into several smaller linear fades. The split should make each fade step has a divisible total_cycle_num/duty_delta (or its inverse) ratio.
ESP_OK Success
ESP_ERR_INVALID_ARG Parameter error
ESP_ERR_INVALID_STATE Channel not initialized
ESP_FAIL Fade function init error
Install LEDC fade function. This function will occupy interrupt of LEDC module.
intr_alloc_flags -- Flags used to allocate the interrupt. One or multiple (ORred) ESP_INTR_FLAG_* values. See esp_intr_alloc.h for more info.
ESP_OK Success
ESP_ERR_INVALID_ARG Intr flag error
ESP_ERR_NOT_FOUND Failed to find available interrupt source
ESP_ERR_INVALID_STATE Fade function already installed
Uninstall LEDC fade function.
Start LEDC fading.
Note
Call ledc_fade_func_install() once before calling this function. Call this API right after ledc_set_fade_with_time or ledc_set_fade_with_step before to start fading.
Note
Starting fade operation with this API is not thread-safe, use with care.
Note
For ESP32, hardware does not support any duty change while a fade operation is running in progress on that channel. Other duty operations will have to wait until the fade operation has finished.
speed_mode -- Select the LEDC channel group with specified speed mode. Note that not all targets support high speed mode.
channel -- LEDC channel number
fade_mode -- Whether to block until fading done. See ledc_types.h ledc_fade_mode_t for more info. Note that this function will not return until fading to the target duty if LEDC_FADE_WAIT_DONE mode is selected.
ESP_OK Success
ESP_ERR_INVALID_STATE Channel not initialized or fade function not installed.
ESP_ERR_INVALID_ARG Parameter error.
A thread-safe API to set duty for LEDC channel and return when duty updated.
Note
For ESP32, hardware does not support any duty change while a fade operation is running in progress on that channel. Other duty operations will have to wait until the fade operation has finished.
speed_mode -- Select the LEDC channel group with specified speed mode. Note that not all targets support high speed mode.
channel -- LEDC channel (0 - LEDC_CHANNEL_MAX-1), select from ledc_channel_t
duty -- Set the LEDC duty, the range of duty setting is [0, (2**duty_resolution)]
hpoint -- Set the LEDC hpoint value, the range is [0, (2**duty_resolution)-1]
ESP_OK Success
ESP_ERR_INVALID_STATE Channel not initialized
ESP_ERR_INVALID_ARG Parameter error
ESP_FAIL Fade function init error
A thread-safe API to set and start LEDC fade function, with a limited time.
Note
Call ledc_fade_func_install() once, before calling this function.
Note
For ESP32, hardware does not support any duty change while a fade operation is running in progress on that channel. Other duty operations will have to wait until the fade operation has finished.
speed_mode -- Select the LEDC channel group with specified speed mode. Note that not all targets support high speed mode.
channel -- LEDC channel index (0 - LEDC_CHANNEL_MAX-1), select from ledc_channel_t
target_duty -- Target duty of fading [0, (2**duty_resolution)]
desired_fade_time_ms -- The intended time of the fading ( ms ). Note that the actual time it takes to complete the fade could vary by a factor of up to 2x shorter or longer than the expected time due to internal rounding errors in calculations. Specifically:
The total number of cycles (total_cycle_num = desired_fade_time_ms * freq / 1000)
The difference in duty cycle (duty_delta = |target_duty - current_duty|) The fade may complete faster than expected if total_cycle_num larger than duty_delta. Conversely, it may take longer than expected if total_cycle_num is less than duty_delta. The closer the ratio of total_cycle_num/duty_delta (or its inverse) is to a whole number (the floor value), the more accurately the actual fade duration will match the intended time. If an exact fade time is expected, please consider to split the entire fade into several smaller linear fades. The split should make each fade step has a divisible total_cycle_num/duty_delta (or its inverse) ratio.
fade_mode -- choose blocking or non-blocking mode
ESP_OK Success
ESP_ERR_INVALID_ARG Parameter error
ESP_ERR_INVALID_STATE Channel not initialized
ESP_FAIL Fade function init error
A thread-safe API to set and start LEDC fade function.
Note
Call ledc_fade_func_install() once before calling this function.
Note
For ESP32, hardware does not support any duty change while a fade operation is running in progress on that channel. Other duty operations will have to wait until the fade operation has finished.
speed_mode -- Select the LEDC channel group with specified speed mode. Note that not all targets support high speed mode.
channel -- LEDC channel index (0 - LEDC_CHANNEL_MAX-1), select from ledc_channel_t
target_duty -- Target duty of fading [0, (2**duty_resolution)]
scale -- Controls the increase or decrease step scale.
cycle_num -- increase or decrease the duty every cycle_num cycles
fade_mode -- choose blocking or non-blocking mode
ESP_OK Success
ESP_ERR_INVALID_ARG Parameter error
ESP_ERR_INVALID_STATE Channel not initialized
ESP_FAIL Fade function init error
LEDC callback registration function.
Note
The callback is called from an ISR, it must never attempt to block, and any FreeRTOS API called must be ISR capable.
speed_mode -- Select the LEDC channel group with specified speed mode. Note that not all targets support high speed mode.
channel -- LEDC channel index (0 - LEDC_CHANNEL_MAX-1), select from ledc_channel_t
cbs -- Group of LEDC callback functions
user_arg -- user registered data for the callback function
ESP_OK Success
ESP_ERR_INVALID_ARG Parameter error
ESP_ERR_INVALID_STATE Channel not initialized
ESP_FAIL Fade function init error
Configuration parameters of LEDC channel for ledc_channel_config function.
Public Members
the LEDC output gpio_num, if you want to use gpio16, gpio_num = 16
LEDC speed speed_mode, high-speed mode (only exists on esp32) or low-speed mode
LEDC channel (0 - LEDC_CHANNEL_MAX-1)
, no need to explicitly configure interrupt, handled in the driver
Select the timer source of channel (0 - LEDC_TIMER_MAX-1)
LEDC channel duty, the range of duty setting is [0, (2**duty_resolution)]
LEDC channel hpoint value, the range is [0, (2**duty_resolution)-1]
choose the desired behavior for the LEDC channel in Light-sleep
Enable (1) or disable (0) gpio output invert
LEDC flags
Configuration parameters of LEDC timer for ledc_timer_config function.
Public Members
LEDC speed speed_mode, high-speed mode (only exists on esp32) or low-speed mode
LEDC channel duty resolution
The timer source of channel (0 - LEDC_TIMER_MAX-1)
LEDC timer frequency (Hz)
Configure LEDC source clock from ledc_clk_cfg_t. Note that LEDC_USE_RC_FAST_CLK and LEDC_USE_XTAL_CLK are non-timer-specific clock sources. You can not have one LEDC timer uses RC_FAST_CLK as the clock source and have another LEDC timer uses XTAL_CLK as its clock source. All chips except esp32 and esp32s2 do not have timer-specific clock sources, which means clock source for all timers must be the same one.
Set this field to de-configure a LEDC timer which has been configured before Note that it will not check whether the timer wants to be de-configured is binded to any channel. Also, the timer has to be paused first before it can be de-configured. When this field is set, duty_resolution, freq_hz, clk_cfg fields are ignored.
LEDC callback parameter.
Public Members
Event name
Speed mode of the LEDC channel group
LEDC channel (0 - LEDC_CHANNEL_MAX-1)
LEDC current duty of the channel, the range of duty is [0, (2**duty_resolution)]
Group of supported LEDC callbacks.
Note
The callbacks are all running under ISR environment
Public Members
LEDC fade_end callback function
Type of LEDC event callback.
LEDC callback parameter
User registered data
Whether a high priority task has been waken up by this function
Strategies to be applied to the LEDC channel during system Light-sleep period.
Values:
The default mode: no LEDC output, and no power off the LEDC power domain.
The low-power-consumption mode: no LEDC output, and allow to power off the LEDC power domain. This can save power, but at the expense of more RAM being consumed to save register context. This option is only available on targets that support TOP domain to be powered down.
The high-power-consumption mode: keep LEDC output when the system enters Light-sleep.
Invalid LEDC sleep mode strategy
LEDC callback event type.
Values:
LEDC fade end event
This header file can be included with:
#include "hal/ledc_types.h"
LEDC clock source configuration struct.
In theory, the following enumeration shall be placed in LEDC driver's header. However, as the next enumeration, ledc_clk_src_t, makes the use of some of these values and to avoid mutual inclusion of the headers, we must define it here.
Values:
LEDC high speed speed_mode
LEDC low speed speed_mode
LEDC speed limit
Values:
Disable LEDC interrupt
Enable LEDC interrupt
Values:
LEDC duty decrease direction
LEDC duty increase direction
LEDC global clock sources.
Values:
LEDC low speed timer clock source is RC_FAST clock
LEDC low speed timer clock source is 80MHz APB clock
Alias of 'LEDC_SLOW_CLK_RC_FAST'
LEDC timer-specific clock sources.
Note: Setting numeric values to match ledc_clk_cfg_t values are a hack to avoid collision with LEDC_AUTO_CLK in the driver, as these enums have very similar names and user may pass one of these by mistake.
Values:
LEDC timer clock divided from reference tick (1Mhz)
LEDC timer clock divided from APB clock (80Mhz)
Selecting this value for LEDC_TICK_SEL_TIMER let the hardware take its source clock from LEDC_APB_CLK_SEL
Values:
LEDC timer 0
LEDC timer 1
LEDC timer 2
LEDC timer 3
Values:
LEDC channel 0
LEDC channel 1
LEDC channel 2
LEDC channel 3
LEDC channel 4
LEDC channel 5
LEDC channel 6
LEDC channel 7
Values:
LEDC PWM duty resolution of 1 bits
LEDC PWM duty resolution of 2 bits
LEDC PWM duty resolution of 3 bits
LEDC PWM duty resolution of 4 bits
LEDC PWM duty resolution of 5 bits
LEDC PWM duty resolution of 6 bits
LEDC PWM duty resolution of 7 bits
LEDC PWM duty resolution of 8 bits
LEDC PWM duty resolution of 9 bits
LEDC PWM duty resolution of 10 bits
LEDC PWM duty resolution of 11 bits
LEDC PWM duty resolution of 12 bits
LEDC PWM duty resolution of 13 bits
LEDC PWM duty resolution of 14 bits
LEDC PWM duty resolution of 15 bits
LEDC PWM duty resolution of 16 bits
LEDC PWM duty resolution of 17 bits
LEDC PWM duty resolution of 18 bits
LEDC PWM duty resolution of 19 bits
LEDC PWM duty resolution of 20 bits
Values:
LEDC fade function will return immediately
LEDC fade function will block until fading to the target duty
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