diff --git a/README.md b/README.md
index c74d19b..41ee54d 100644
--- a/README.md
+++ b/README.md
@@ -118,7 +118,7 @@ int main()
 	button_attach(&btn1, SINGLE_CLICK,     BTN1_SINGLE_Click_Handler);
 	button_attach(&btn1, DOUBLE_CLICK,     BTN1_DOUBLE_Click_Handler);
 	button_attach(&btn1, LONG_PRESS_START, BTN1_LONG_PRESS_START_Handler);
-	button_attach(&btn2, LONG_PRESS_HOLD,  BTN1_LONG_PRESS_HOLD_Handler);
+	button_attach(&btn1, LONG_PRESS_HOLD,  BTN1_LONG_PRESS_HOLD_Handler);
 	button_start(&btn1);
 
 	//make the timer invoking the button_ticks() interval 5ms.
@@ -129,5 +129,3 @@ int main()
 	{}
 }
 ```
-
-
diff --git a/examples/example_poll.c b/examples/example_poll.c
index eb06029..8dec531 100644
--- a/examples/example_poll.c
+++ b/examples/example_poll.c
@@ -18,7 +18,7 @@ uint8_t read_button_GPIO(uint8_t button_id)
 
 int main()
 {
-	static uint8_t btn1_event_val;
+	static PressEvent btn1_event_val;
 
 	button_init(&btn1, read_button_GPIO, 0, btn1_id);
 	button_start(&btn1);
diff --git a/multi_button.c b/multi_button.c
index 6b09dc8..d1861e3 100644
--- a/multi_button.c
+++ b/multi_button.c
@@ -10,10 +10,12 @@
 //button handle list head.
 static struct Button* head_handle = NULL;
 
+static void button_handler(struct Button* handle);
+
 /**
   * @brief  Initializes the button struct handle.
-  * @param  handle: the button handle strcut.
-  * @param  pin_level: read the HAL GPIO of the connet button level.
+  * @param  handle: the button handle struct.
+  * @param  pin_level: read the HAL GPIO of the connected button level.
   * @param  active_level: pressed GPIO level.
   * @param  button_id: the button id.
   * @retval None
@@ -30,7 +32,7 @@ void button_init(struct Button* handle, uint8_t(*pin_level)(uint8_t), uint8_t ac
 
 /**
   * @brief  Attach the button event callback function.
-  * @param  handle: the button handle strcut.
+  * @param  handle: the button handle struct.
   * @param  event: trigger event type.
   * @param  cb: callback function.
   * @retval None
@@ -42,7 +44,7 @@ void button_attach(struct Button* handle, PressEvent event, BtnCallback cb)
 
 /**
   * @brief  Inquire the button event happen.
-  * @param  handle: the button handle strcut.
+  * @param  handle: the button handle struct.
   * @retval button event.
   */
 PressEvent get_button_event(struct Button* handle)
@@ -52,10 +54,10 @@ PressEvent get_button_event(struct Button* handle)
 
 /**
   * @brief  Button driver core function, driver state machine.
-  * @param  handle: the button handle strcut.
+  * @param  handle: the button handle struct.
   * @retval None
   */
-void button_handler(struct Button* handle)
+static void button_handler(struct Button* handle)
 {
 	uint8_t read_gpio_level = handle->hal_button_Level(handle->button_id);
 
@@ -69,7 +71,7 @@ void button_handler(struct Button* handle)
 			handle->button_level = read_gpio_level;
 			handle->debounce_cnt = 0;
 		}
-	} else { //leved not change ,counter reset.
+	} else { //level not change ,counter reset.
 		handle->debounce_cnt = 0;
 	}
 
@@ -93,7 +95,6 @@ void button_handler(struct Button* handle)
 			EVENT_CB(PRESS_UP);
 			handle->ticks = 0;
 			handle->state = 2;
-
 		} else if(handle->ticks > LONG_TICKS) {
 			handle->event = (uint8_t)LONG_PRESS_START;
 			EVENT_CB(LONG_PRESS_START);
@@ -131,7 +132,7 @@ void button_handler(struct Button* handle)
 			} else {
 				handle->state = 0;
 			}
-		}else if(handle->ticks > SHORT_TICKS){ // long press up
+		} else if(handle->ticks > SHORT_TICKS) { // long press up
 			handle->state = 0;
 		}
 		break;
@@ -141,22 +142,21 @@ void button_handler(struct Button* handle)
 			//continue hold trigger
 			handle->event = (uint8_t)LONG_PRESS_HOLD;
 			EVENT_CB(LONG_PRESS_HOLD);
-
 		} else { //releasd
 			handle->event = (uint8_t)PRESS_UP;
 			EVENT_CB(PRESS_UP);
 			handle->state = 0; //reset
 		}
 		break;
-    default:
-        handle->state = 0; //reset
-        break;
+	default:
+		handle->state = 0; //reset
+		break;
 	}
 }
 
 /**
   * @brief  Start the button work, add the handle into work list.
-  * @param  handle: target handle strcut.
+  * @param  handle: target handle struct.
   * @retval 0: succeed. -1: already exist.
   */
 int button_start(struct Button* handle)
@@ -173,7 +173,7 @@ int button_start(struct Button* handle)
 
 /**
   * @brief  Stop the button work, remove the handle off work list.
-  * @param  handle: target handle strcut.
+  * @param  handle: target handle struct.
   * @retval None
   */
 void button_stop(struct Button* handle)
@@ -181,12 +181,13 @@ void button_stop(struct Button* handle)
 	struct Button** curr;
 	for(curr = &head_handle; *curr; ) {
 		struct Button* entry = *curr;
-		if (entry == handle) {
+		if(entry == handle) {
 			*curr = entry->next;
 //			free(entry);
 			return;//glacier add 2021-8-18
-		} else
+		} else {
 			curr = &entry->next;
+		}
 	}
 }
 
@@ -195,7 +196,7 @@ void button_stop(struct Button* handle)
   * @param  None.
   * @retval None
   */
-void button_ticks()
+void button_ticks(void)
 {
 	struct Button* target;
 	for(target=head_handle; target; target=target->next) {
diff --git a/multi_button.h b/multi_button.h
index c468458..a5bfc99 100644
--- a/multi_button.h
+++ b/multi_button.h
@@ -11,7 +11,7 @@
 
 //According to your need to modify the constants.
 #define TICKS_INTERVAL    5	//ms
-#define DEBOUNCE_TICKS    3	//MAX 8
+#define DEBOUNCE_TICKS    3	//MAX 7 (0 ~ 7)
 #define SHORT_TICKS       (300 /TICKS_INTERVAL)
 #define LONG_TICKS        (1000 /TICKS_INTERVAL)