Add some comments in pcnt.h.

components/driver/include/driver/pcnt.h

@@ -98,6 +98,8 @@ typedef intr_handle_t pcnt_isr_handle_t;
 
 /**
  * @brief Configure Pulse Counter unit
+ *        @note
+ *        This function will disable three events: PCNT_EVT_L_LIM, PCNT_EVT_H_LIM, PCNT_EVT_ZERO.
  *
  * @param pcnt_config Pointer of Pulse Counter unit configure parameter
  *
@@ -233,16 +235,19 @@ esp_err_t pcnt_get_event_value(pcnt_unit_t unit, pcnt_evt_type_t evt_type, int16
 /**
  * @brief Register PCNT interrupt handler, the handler is an ISR.
  *        The handler will be attached to the same CPU core that this function is running on.
+ *        Please do not use pcnt_isr_service_install if this function was called.
  *
  * @param fn Interrupt handler function.
  * @param arg Parameter for handler function
  * @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.
  * @param handle Pointer to return handle. If non-NULL, a handle for the interrupt will
- *        be returned here.
+ *        be returned here. Calling esp_intr_free to unregister this ISR service if needed,
+ *        but only if the handle is not NULL.
  *
  * @return
  *     - ESP_OK Success
+ *     - ESP_ERR_NOT_FOUND Can not find the interrupt that matches the flags.
  *     - ESP_ERR_INVALID_ARG Function pointer error.
  */
 esp_err_t pcnt_isr_register(void (*fn)(void*), void * arg, int intr_alloc_flags, pcnt_isr_handle_t *handle);
@@ -358,7 +363,8 @@ esp_err_t pcnt_isr_handler_add(pcnt_unit_t unit, void(*isr_handler)(void *), voi
 /**
  * @brief Install PCNT ISR service.
  * @note We can manage different interrupt service for each unit.
- *       Please do not use pcnt_isr_register if this function was called.
+ *       This function will use the default ISR handle service, Calling pcnt_isr_service_uninstall to
+ *       uninstall the default service if needed. Please do not use pcnt_isr_register if this function was called. 
  *
  * @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.

components/driver/pcnt.c

@@ -24,6 +24,7 @@
 #define PCNT_COUNT_MODE_ERR_STR "PCNT COUNTER MODE ERROR"
 #define PCNT_CTRL_MODE_ERR_STR  "PCNT CTRL MODE ERROR"
 #define PCNT_EVT_TYPE_ERR_STR   "PCNT value type error"
+#define PCNT_LIMT_VAL_ERR_STR   "PCNT limit value error"
 
 #define PCNT_ENTER_CRITICAL(mux)    portENTER_CRITICAL(mux)
 #define PCNT_EXIT_CRITICAL(mux)     portEXIT_CRITICAL(mux)
@@ -221,6 +222,8 @@ esp_err_t pcnt_set_event_value(pcnt_unit_t unit, pcnt_evt_type_t evt_type, int16
 {
     PCNT_CHECK(unit < PCNT_UNIT_MAX, PCNT_UNIT_ERR_STR, ESP_ERR_INVALID_ARG);
     PCNT_CHECK(evt_type < PCNT_EVT_MAX, PCNT_EVT_TYPE_ERR_STR, ESP_ERR_INVALID_ARG);
+    PCNT_CHECK(!(evt_type == PCNT_EVT_L_LIM && value > 0), PCNT_LIMT_VAL_ERR_STR, ESP_ERR_INVALID_ARG);
+    PCNT_CHECK(!(evt_type == PCNT_EVT_H_LIM && value < 0), PCNT_LIMT_VAL_ERR_STR, ESP_ERR_INVALID_ARG);
     if(evt_type == PCNT_EVT_L_LIM) {
         PCNT.conf_unit[unit].conf2.cnt_l_lim = value;
     } else if(evt_type == PCNT_EVT_H_LIM) {

examples/peripherals/pcnt/main/pcnt_example_main.c

@@ -54,6 +54,7 @@
 #define LEDC_OUTPUT_IO      18 // Output GPIO of a sample 1 Hz pulse generator
 
 xQueueHandle pcnt_evt_queue;   // A queue to handle pulse counter events
+pcnt_isr_handle_t user_isr_handle = NULL; //user's ISR service handle
 
 /* A sample structure to pass events from the PCNT
  * interrupt handler to the main program.
@@ -159,7 +160,7 @@ static void pcnt_example_init(void)
     pcnt_counter_clear(PCNT_TEST_UNIT);
 
     /* Register ISR handler and enable interrupts for PCNT unit */
-    pcnt_isr_register(pcnt_example_intr_handler, NULL, 0, NULL);
+    pcnt_isr_register(pcnt_example_intr_handler, NULL, 0, &user_isr_handle);
     pcnt_intr_enable(PCNT_TEST_UNIT);
 
     /* Everything is set up, now go to counting */
@@ -206,4 +207,9 @@ void app_main()
             printf("Current counter value :%d\n", count);
         }
     }
+    if(user_isr_handle) {
+        //Free the ISR service handle.
+        esp_intr_free(user_isr_handle);
+        user_isr_handle = NULL;
+    }
 }