fix(ledc): fix ledc driver 100% duty cycle configuration

Update ledc duty cycle value range in doxygen.
Fix duty configuration error at 100% duty cycle for ESP32.
Improve LEDC API doxygen.

Closes https://github.com/espressif/esp-idf/pull/11516
Closes https://github.com/espressif/esp-idf/issues/12593
Closes https://github.com/espressif/esp-idf/issues/12083

components/driver/include/driver/ledc.h

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2015-2021 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2015-2023 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -27,12 +27,12 @@ extern "C" {
  */
 typedef struct {
     int gpio_num;                   /*!< the LEDC output gpio_num, if you want to use gpio16, gpio_num = 16 */
-    ledc_mode_t speed_mode;         /*!< LEDC speed speed_mode, high-speed mode or low-speed mode */
+    ledc_mode_t speed_mode;         /*!< LEDC speed speed_mode, high-speed mode (only exists on esp32) or low-speed mode */
     ledc_channel_t channel;         /*!< LEDC channel (0 - 7) */
     ledc_intr_type_t intr_type;     /*!< configure interrupt, Fade interrupt enable  or Fade interrupt disable */
     ledc_timer_t timer_sel;         /*!< Select the timer source of channel (0 - 3) */
     uint32_t duty;                  /*!< LEDC channel duty, the range of duty setting is [0, (2**duty_resolution)] */
-    int hpoint;                     /*!< LEDC channel hpoint value, the max value is 0xfffff */
+    int hpoint;                     /*!< LEDC channel hpoint value, the range is [0, (2**duty_resolution)-1] */
     struct {
         unsigned int output_invert: 1;/*!< Enable (1) or disable (0) gpio output invert */
     } flags;                        /*!< LEDC flags */
@@ -43,7 +43,7 @@ typedef struct {
  * @brief Configuration parameters of LEDC Timer timer for ledc_timer_config function
  */
 typedef struct {
-    ledc_mode_t speed_mode;                /*!< LEDC speed speed_mode, high-speed mode or low-speed mode */
+    ledc_mode_t speed_mode;                /*!< LEDC speed speed_mode, high-speed mode (only exists on esp32) or low-speed mode */
     union {
         ledc_timer_bit_t duty_resolution;  /*!< LEDC channel duty resolution */
         ledc_timer_bit_t bit_num __attribute__((deprecated)); /*!< Deprecated in ESP-IDF 3.0. This is an alias to 'duty_resolution' for backward compatibility with ESP-IDF 2.1 */
@@ -71,7 +71,7 @@ typedef struct {
     ledc_cb_event_t event;              /**< Event name */
     uint32_t speed_mode;                /**< Speed mode of the LEDC channel group */
     uint32_t channel;                   /**< LEDC channel (0 - LEDC_CHANNEL_MAX-1) */
-    uint32_t duty;                      /**< LEDC current duty of the channel, the range of duty is [0, (2**duty_resolution) - 1] */
+    uint32_t duty;                      /**< LEDC current duty of the channel, the range of duty is [0, (2**duty_resolution)] */
 } ledc_cb_param_t;
 
 /**
@@ -117,6 +117,7 @@ esp_err_t ledc_timer_config(const ledc_timer_config_t *timer_conf);
 
 /**
  * @brief 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.
@@ -129,7 +130,6 @@ esp_err_t ledc_timer_config(const ledc_timer_config_t *timer_conf);
  * @return
  *     - ESP_OK Success
  *     - ESP_ERR_INVALID_ARG Parameter error
- *
  */
 esp_err_t ledc_update_duty(ledc_mode_t speed_mode, ledc_channel_t channel);
 
@@ -190,15 +190,17 @@ uint32_t ledc_get_freq(ledc_mode_t speed_mode, ledc_timer_t timer_num);
 /**
  * @brief 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  If a fade operation is running in progress on that channel, the driver would not allow it to be stopped.
  *        Other duty operations will have to wait until the fade operation has finished.
+ *
  * @param speed_mode Select the LEDC channel group with specified speed mode. Note that not all targets support high speed mode.
  * @param channel LEDC channel (0 - LEDC_CHANNEL_MAX-1), select from ledc_channel_t
- * @param duty Set the LEDC duty, the range of duty setting is [0, (2**duty_resolution) - 1]
- * @param hpoint Set the LEDC hpoint value(max: 0xfffff)
+ * @param duty Set the LEDC duty, the range of duty setting is [0, (2**duty_resolution)]
+ * @param hpoint Set the LEDC hpoint value, the range is [0, (2**duty_resolution)-1]
  *
  * @return
  *     - ESP_OK Success
@@ -211,6 +213,7 @@ esp_err_t ledc_set_duty_with_hpoint(ledc_mode_t speed_mode, ledc_channel_t chann
  *
  * @param speed_mode Select the LEDC channel group with specified speed mode. Note that not all targets support high speed mode.
  * @param channel LEDC channel (0 - LEDC_CHANNEL_MAX-1), select from ledc_channel_t
+ *
  * @return
  *     - LEDC_ERR_VAL if parameter error
  *     - Others Current hpoint value of LEDC channel
@@ -221,14 +224,16 @@ int ledc_get_hpoint(ledc_mode_t speed_mode, ledc_channel_t channel);
  * @brief 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  If a fade operation is running in progress on that channel, the driver would not allow it to be stopped.
  *        Other duty operations will have to wait until the fade operation has finished.
+ *
  * @param speed_mode Select the LEDC channel group with specified speed mode. Note that not all targets support high speed mode.
  * @param channel LEDC channel (0 - LEDC_CHANNEL_MAX-1), select from ledc_channel_t
- * @param duty Set the LEDC duty, the range of duty setting is [0, (2**duty_resolution) - 1]
+ * @param duty Set the LEDC duty, the range of duty setting is [0, (2**duty_resolution)]
  *
  * @return
  *     - ESP_OK Success
@@ -256,9 +261,10 @@ uint32_t ledc_get_duty(ledc_mode_t speed_mode, ledc_channel_t channel);
  *        Set LEDC gradient, After the function calls the ledc_update_duty function, the function can take effect.
  * @note  If a fade operation is running in progress on that channel, the driver would not allow it to be stopped.
  *        Other duty operations will have to wait until the fade operation has finished.
+ *
  * @param speed_mode Select the LEDC channel group with specified speed mode. Note that not all targets support high speed mode.
  * @param channel LEDC channel (0 - LEDC_CHANNEL_MAX-1), select from ledc_channel_t
- * @param duty Set the start of the gradient duty, the range of duty setting is [0, (2**duty_resolution) - 1]
+ * @param duty Set the start of the gradient duty, the range of duty setting is [0, (2**duty_resolution)]
  * @param fade_direction Set the direction of the gradient
  * @param step_num Set the number of the gradient
  * @param duty_cycle_num Set how many LEDC tick each time the gradient lasts
@@ -284,7 +290,8 @@ esp_err_t ledc_set_fade(ledc_mode_t speed_mode, ledc_channel_t channel, uint32_t
  *
  * @return
  *     - ESP_OK Success
- *     - ESP_ERR_INVALID_ARG Function pointer error.
+ *     - ESP_ERR_INVALID_ARG Parameter error
+ *     - ESP_ERR_NOT_FOUND Failed to find available interrupt source
  */
 esp_err_t ledc_isr_register(void (*fn)(void *), void *arg, int intr_alloc_flags, ledc_isr_handle_t *handle);
 
@@ -294,7 +301,7 @@ esp_err_t ledc_isr_register(void (*fn)(void *), void *arg, int intr_alloc_flags,
  * @param speed_mode Select the LEDC channel group with specified speed mode. Note that not all targets support high speed mode.
  * @param timer_sel  Timer index (0-3), there are 4 timers in LEDC module
  * @param clock_divider Timer clock divide value, the timer clock is divided from the selected clock source
- * @param duty_resolution Resolution of duty setting in number of bits. The range of duty values is [0, (2**duty_resolution)]
+ * @param duty_resolution Resolution of duty setting in number of bits. The range is [1, SOC_LEDC_TIMER_BIT_WIDTH]
  * @param clk_src Select LEDC source clock.
  *
  * @return
@@ -324,7 +331,6 @@ esp_err_t ledc_timer_rst(ledc_mode_t speed_mode, ledc_timer_t timer_sel);
  * @return
  *     - ESP_ERR_INVALID_ARG Parameter error
  *     - ESP_OK Success
- *
  */
 esp_err_t ledc_timer_pause(ledc_mode_t speed_mode, ledc_timer_t timer_sel);
 
@@ -355,6 +361,7 @@ esp_err_t ledc_bind_channel_timer(ledc_mode_t speed_mode, ledc_channel_t channel
 
 /**
  * @brief 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
@@ -362,22 +369,24 @@ esp_err_t ledc_bind_channel_timer(ledc_mode_t speed_mode, ledc_channel_t channel
  *        A thread-safe version of API is ledc_set_fade_step_and_start
  * @note  If a fade operation is running in progress on that channel, the driver would not allow it to be stopped.
  *        Other duty operations will have to wait until the fade operation has finished.
- * @param speed_mode Select the LEDC channel group with specified speed mode. Note that not all targets support high speed mode. ,
+ *
+ * @param speed_mode Select the LEDC channel group with specified speed mode. Note that not all targets support high speed mode.
  * @param channel LEDC channel index (0 - LEDC_CHANNEL_MAX-1), select from ledc_channel_t
- * @param target_duty Target duty of fading [0, (2**duty_resolution) - 1]
+ * @param target_duty Target duty of fading [0, (2**duty_resolution)]
  * @param scale Controls the increase or decrease step scale.
  * @param cycle_num increase or decrease the duty every cycle_num cycles
  *
  * @return
- *     - ESP_ERR_INVALID_ARG Parameter error
  *     - ESP_OK Success
- *     - ESP_ERR_INVALID_STATE Fade function not installed.
+ *     - ESP_ERR_INVALID_ARG Parameter error
+ *     - ESP_ERR_INVALID_STATE Channel not initialized
  *     - ESP_FAIL Fade function init error
  */
 esp_err_t ledc_set_fade_with_step(ledc_mode_t speed_mode, ledc_channel_t channel, uint32_t target_duty, uint32_t scale, uint32_t cycle_num);
 
 /**
  * @brief 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
@@ -385,42 +394,47 @@ esp_err_t ledc_set_fade_with_step(ledc_mode_t speed_mode, ledc_channel_t channel
  *        A thread-safe version of API is ledc_set_fade_step_and_start
  * @note  If a fade operation is running in progress on that channel, the driver would not allow it to be stopped.
  *        Other duty operations will have to wait until the fade operation has finished.
- * @param speed_mode Select the LEDC channel group with specified speed mode. Note that not all targets support high speed mode. ,
+ *
+ * @param speed_mode Select the LEDC channel group with specified speed mode. Note that not all targets support high speed mode.
  * @param channel LEDC channel index (0 - LEDC_CHANNEL_MAX-1), select from ledc_channel_t
- * @param target_duty Target duty of fading [0, (2**duty_resolution) - 1]
+ * @param target_duty Target duty of fading [0, (2**duty_resolution)]
  * @param max_fade_time_ms The maximum time of the fading ( ms ).
  *
  * @return
- *     - ESP_ERR_INVALID_ARG Parameter error
  *     - ESP_OK Success
- *     - ESP_ERR_INVALID_STATE Fade function not installed.
+ *     - ESP_ERR_INVALID_ARG Parameter error
+ *     - ESP_ERR_INVALID_STATE Channel not initialized
  *     - ESP_FAIL Fade function init error
  */
 esp_err_t ledc_set_fade_with_time(ledc_mode_t speed_mode, ledc_channel_t channel, uint32_t target_duty, int max_fade_time_ms);
 
 /**
  * @brief Install LEDC fade function. This function will occupy interrupt of LEDC module.
+ *
  * @param 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.
  *
  * @return
  *     - ESP_OK Success
- *     - ESP_ERR_INVALID_STATE Fade function already installed.
+ *     - 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
  */
 esp_err_t ledc_fade_func_install(int intr_alloc_flags);
 
 /**
  * @brief Uninstall LEDC fade function.
- *
  */
 void ledc_fade_func_uninstall(void);
 
 /**
  * @brief 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  If a fade operation is running in progress on that channel, the driver would not allow it to be stopped.
  *        Other duty operations will have to wait until the fade operation has finished.
+ *
  * @param speed_mode Select the LEDC channel group with specified speed mode. Note that not all targets support high speed mode.
  * @param channel LEDC channel number
  * @param fade_mode Whether to block until fading done. See ledc_types.h ledc_fade_mode_t for more info.
@@ -428,7 +442,7 @@ void ledc_fade_func_uninstall(void);
  *
  * @return
  *     - ESP_OK Success
- *     - ESP_ERR_INVALID_STATE Fade function not installed.
+ *     - ESP_ERR_INVALID_STATE Channel not initialized or fade function not installed.
  *     - ESP_ERR_INVALID_ARG Parameter error.
  */
 esp_err_t ledc_fade_start(ledc_mode_t speed_mode, ledc_channel_t channel, ledc_fade_mode_t fade_mode);
@@ -440,60 +454,74 @@ esp_err_t ledc_fade_start(ledc_mode_t speed_mode, ledc_channel_t channel, ledc_f
  *
  * @param speed_mode Select the LEDC channel group with specified speed mode. Note that not all targets support high speed mode.
  * @param channel LEDC channel (0 - LEDC_CHANNEL_MAX-1), select from ledc_channel_t
- * @param duty Set the LEDC duty, the range of duty setting is [0, (2**duty_resolution) - 1]
- * @param hpoint Set the LEDC hpoint value(max: 0xfffff)
+ * @param duty Set the LEDC duty, the range of duty setting is [0, (2**duty_resolution)]
+ * @param hpoint Set the LEDC hpoint value, the range is [0, (2**duty_resolution)-1]
  *
+ * @return
+ *      - ESP_OK Success
+ *      - ESP_ERR_INVALID_STATE Channel not initialized
+ *      - ESP_ERR_INVALID_ARG Parameter error
+ *      - ESP_FAIL Fade function init error
  */
 esp_err_t ledc_set_duty_and_update(ledc_mode_t speed_mode, ledc_channel_t channel, uint32_t duty, uint32_t hpoint);
 
 /**
  * @brief 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  If a fade operation is running in progress on that channel, the driver would not allow it to be stopped.
  *        Other duty operations will have to wait until the fade operation has finished.
+ *
  * @param speed_mode Select the LEDC channel group with specified speed mode. Note that not all targets support high speed mode.
  * @param channel LEDC channel index (0 - LEDC_CHANNEL_MAX-1), select from ledc_channel_t
- * @param target_duty Target duty of fading [0, (2**duty_resolution) - 1]
+ * @param target_duty Target duty of fading [0, (2**duty_resolution)]
  * @param max_fade_time_ms The maximum time of the fading ( ms ).
  * @param fade_mode choose blocking or non-blocking mode
+ *
  * @return
- *     - ESP_ERR_INVALID_ARG Parameter error
  *     - ESP_OK Success
- *     - ESP_ERR_INVALID_STATE Fade function not installed.
+ *     - ESP_ERR_INVALID_ARG Parameter error
+ *     - ESP_ERR_INVALID_STATE Channel not initialized
  *     - ESP_FAIL Fade function init error
  */
 esp_err_t ledc_set_fade_time_and_start(ledc_mode_t speed_mode, ledc_channel_t channel, uint32_t target_duty, uint32_t max_fade_time_ms, ledc_fade_mode_t fade_mode);
 
 /**
  * @brief A thread-safe API to set and start LEDC fade function.
+ *
  * @note  Call ledc_fade_func_install() once before calling this function.
  * @note  If a fade operation is running in progress on that channel, the driver would not allow it to be stopped.
  *        Other duty operations will have to wait until the fade operation has finished.
+ *
  * @param speed_mode Select the LEDC channel group with specified speed mode. Note that not all targets support high speed mode.
  * @param channel LEDC channel index (0 - LEDC_CHANNEL_MAX-1), select from ledc_channel_t
- * @param target_duty Target duty of fading [0, (2**duty_resolution) - 1]
+ * @param target_duty Target duty of fading [0, (2**duty_resolution)]
  * @param scale Controls the increase or decrease step scale.
  * @param cycle_num increase or decrease the duty every cycle_num cycles
  * @param fade_mode choose blocking or non-blocking mode
+ *
  * @return
- *     - ESP_ERR_INVALID_ARG Parameter error
  *     - ESP_OK Success
- *     - ESP_ERR_INVALID_STATE Fade function not installed.
+ *     - ESP_ERR_INVALID_ARG Parameter error
+ *     - ESP_ERR_INVALID_STATE Channel not initialized
  *     - ESP_FAIL Fade function init error
  */
 esp_err_t ledc_set_fade_step_and_start(ledc_mode_t speed_mode, ledc_channel_t channel, uint32_t target_duty, uint32_t scale, uint32_t cycle_num, ledc_fade_mode_t fade_mode);
 
 /**
  * @brief 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.
+ *
  * @param speed_mode Select the LEDC channel group with specified speed mode. Note that not all targets support high speed mode.
  * @param channel LEDC channel index (0 - LEDC_CHANNEL_MAX-1), select from ledc_channel_t
  * @param cbs Group of LEDC callback functions
  * @param user_arg user registered data for the callback function
+ *
  * @return
- *     - ESP_ERR_INVALID_ARG Parameter error
  *     - ESP_OK Success
- *     - ESP_ERR_INVALID_STATE Fade function not installed.
+ *     - ESP_ERR_INVALID_ARG Parameter error
+ *     - ESP_ERR_INVALID_STATE Channel not initialized
  *     - ESP_FAIL Fade function init error
  */
 esp_err_t ledc_cb_register(ledc_mode_t speed_mode, ledc_channel_t channel, ledc_cbs_t *cbs, void *user_arg);

components/driver/ledc.c

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2015-2021 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2015-2023 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -621,8 +621,13 @@ esp_err_t ledc_channel_config(const ledc_channel_config_t* ledc_conf)
     }
 
     /*set channel parameters*/
-    /*   channel parameters decide how the waveform looks like in one period*/
-    /*   set channel duty and hpoint value, duty range is (0 ~ ((2 ** duty_resolution) - 1)), max hpoint value is 0xfffff*/
+    /*   channel parameters decide how the waveform looks like in one period */
+    /*   set channel duty and hpoint value, duty range is [0, (2**duty_res)], hpoint range is [0, (2**duty_res)-1] */
+    /*   Note: On ESP32, ESP32S2, ESP32S3, ESP32C3 due to a hardware bug,
+     *         100% duty cycle (i.e. 2**duty_res) is not reachable when the binded timer selects the maximum duty
+     *         resolution. For example, the max duty resolution on ESP32C3 is 14-bit width, then set duty to (2**14)
+     *         will mess up the duty calculation in hardware.
+    */
     ledc_set_duty_with_hpoint(speed_mode, ledc_channel, duty, hpoint);
     /*update duty settings*/
     ledc_update_duty(speed_mode, ledc_channel);
@@ -790,7 +795,7 @@ static inline void ledc_calc_fade_end_channel(uint32_t *fade_end_status, uint32_
     *channel = i;
 }
 
-void IRAM_ATTR ledc_fade_isr(void* arg)
+static void IRAM_ATTR ledc_fade_isr(void* arg)
 {
     bool cb_yield = false;
     portBASE_TYPE HPTaskAwoken = pdFALSE;
@@ -953,7 +958,8 @@ static esp_err_t _ledc_set_fade_with_step(ledc_mode_t speed_mode, ledc_channel_t
         ESP_LOGD(LEDC_TAG, "cur duty: %d; target: %d, step: %d, cycle: %d; scale: %d; dir: %d\n",
                 duty_cur, target_duty, step_num, cycle_num, scale, dir);
     } else {
-        ledc_duty_config(speed_mode, channel, LEDC_VAL_NO_CHANGE, target_duty, dir, 0, 1, 0);
+        // Directly set duty to the target, does not care on the dir
+        ledc_duty_config(speed_mode, channel, LEDC_VAL_NO_CHANGE, target_duty, 1, 0, 1, 0);
         ESP_LOGD(LEDC_TAG, "Set to target duty: %d", target_duty);
     }
     return ESP_OK;
@@ -1054,6 +1060,7 @@ esp_err_t ledc_fade_start(ledc_mode_t speed_mode, ledc_channel_t channel, ledc_f
 
 esp_err_t ledc_fade_func_install(int intr_alloc_flags)
 {
+    LEDC_CHECK(s_ledc_fade_isr_handle == NULL, "fade function already installed", ESP_ERR_INVALID_STATE);
     //OR intr_alloc_flags with ESP_INTR_FLAG_IRAM because the fade isr is in IRAM
     return ledc_isr_register(ledc_fade_isr, NULL, intr_alloc_flags | ESP_INTR_FLAG_IRAM, &s_ledc_fade_isr_handle);
 }

docs/en/api-reference/peripherals/ledc.rst

@@ -96,7 +96,13 @@ To set the duty cycle, use the dedicated function :cpp:func:`ledc_set_duty`. Aft
 
 Another way to set the duty cycle, as well as some other channel parameters, is by calling :cpp:func:`ledc_channel_config` covered in Section :ref:`ledc-api-configure-channel`.
 
-The range of the duty cycle values passed to functions depends on selected ``duty_resolution`` and should be from ``0`` to ``(2 ** duty_resolution) - 1``. For example, if the selected duty resolution is 10, then the duty cycle values can range from 0 to 1023. This provides the resolution of ~0.1%.
+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%.
+
+.. only:: esp32 or esp32s2 or esp32s3 or esp32c3
+
+    .. warning::
+
+        On {IDF_TARGET_NAME}, 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.
 
 
 Change PWM Duty Cycle using Hardware

docs/zh_CN/api-reference/peripherals/ledc.rst

@@ -96,7 +96,13 @@ LED PWM 控制器可在无需 CPU 干预的情况下自动改变占空比，实
 
 另外一种设置占空比和其他通道参数的方式是调用 :ref:`ledc-api-configure-channel` 一节提到的函数 :cpp:func:`ledc_channel_config`。
 
-传递给函数的占空比数值范围取决于选定的 ``duty_resolution``，应为 ``0`` 至 ``(2 ** duty_resolution) - 1``。例如，如选定的占空比分辨率为 10，则占空比的数值范围为 0 至 1023。此时分辨率为 ~0.1%。
+传递给函数的占空比数值范围取决于选定的 ``duty_resolution``，应为 ``0`` 至 ``(2 ** duty_resolution)``。例如，如选定的占空比分辨率为 10，则占空比的数值范围为 0 至 1024。此时分辨率为 ~ 0.1%。
+
+.. only:: esp32 or esp32s2 or esp32s3 or esp32c3
+
+    .. warning::
+
+        在 {IDF_TARGET_NAME} 上，当通道绑定的定时器配置了其最大 PWM 占空比分辨率（ ``MAX_DUTY_RES`` ），通道的占空比不能被设置到 ``(2 ** MAX_DUTY_RES)`` 。否则，硬件内部占空比计数器会溢出，并导致占空比计算错误。
 
 
 使用硬件改变 PWM 占空比

examples/peripherals/ledc/ledc_basic/README.md

@@ -24,7 +24,7 @@ The example uses fixed PWM frequency of 5 kHz, duty cycle in 50%, and output GPI
 
 Depending on the selected `LEDC_FREQUENCY`, you will need to change the `LEDC_DUTY_RES`.
 
-To dinamicaly set the duty and frequency, you can use the following functions:
+To dynamically set the duty and frequency, you can use the following functions:
 
 To set the frequency to 2.5 kHZ i.e:
 
@@ -32,10 +32,10 @@ To set the frequency to 2.5 kHZ i.e:
 ledc_set_freq(LEDC_MODE, LEDC_TIMER, 2500);
 ```
 
-Now the duty to 100% i.e:
+Now set the duty to 100% i.e:
 
 ```c
-ledc_set_duty(LEDC_MODE, LEDC_CHANNEL, 8191);
+ledc_set_duty(LEDC_MODE, LEDC_CHANNEL, 8192);
 ledc_update_duty(LEDC_MODE, LEDC_CHANNEL);
 ```
 
@@ -43,7 +43,7 @@ To change the duty cycle you need to calculate the duty range according to the d
 
 If duty resolution is 13 bits:
 
-Duty range: `0 to (2 ** 13) - 1 = 8191` where 0 is 0% and 8191 is 100%.
+Duty range: `0 to (2 ** 13) = 8192` where 0 is 0% and 8192 is 100%.
 
 ### Build and Flash
 

examples/peripherals/ledc/ledc_basic/main/ledc_basic_example_main.c

@@ -15,9 +15,15 @@
 #define LEDC_OUTPUT_IO          (5) // Define the output GPIO
 #define LEDC_CHANNEL            LEDC_CHANNEL_0
 #define LEDC_DUTY_RES           LEDC_TIMER_13_BIT // Set duty resolution to 13 bits
-#define LEDC_DUTY               (4095) // Set duty to 50%. ((2 ** 13) - 1) * 50% = 4095
+#define LEDC_DUTY               (4096) // Set duty to 50%. (2 ** 13) * 50% = 4096
 #define LEDC_FREQUENCY          (5000) // Frequency in Hertz. Set frequency at 5 kHz
 
+/* Warning:
+ * For ESP32, ESP32S2, ESP32S3, ESP32C3 targets,
+ * when LEDC_DUTY_RES selects the maximum duty resolution (i.e. value equal to SOC_LEDC_TIMER_BIT_WIDTH),
+ * 100% duty cycle is not reachable (duty cannot be set to (2 ** SOC_LEDC_TIMER_BIT_WIDTH)).
+ */
+
 static void example_ledc_init(void)
 {
     // Prepare and then apply the LEDC PWM timer configuration