diff --git a/exp1/Core/Inc/main.h b/exp1/Core/Inc/main.h
index 2c97d0a..c92ef5c 100644
--- a/exp1/Core/Inc/main.h
+++ b/exp1/Core/Inc/main.h
@@ -46,14 +46,14 @@ extern "C" {
 
 /* Exported macro ------------------------------------------------------------*/
 /* USER CODE BEGIN EM */
-
+#define SYSTICKCLK 170  // Systick Frequency 170MHz
 /* USER CODE END EM */
 
 /* Exported functions prototypes ---------------------------------------------*/
 void Error_Handler(void);
 
 /* USER CODE BEGIN EFP */
-
+void delay_us(uint32_t nus);
 /* USER CODE END EFP */
 
 /* Private defines -----------------------------------------------------------*/
diff --git a/exp1/Core/Src/main.c b/exp1/Core/Src/main.c
index 56a05b5..ba0990f 100644
--- a/exp1/Core/Src/main.c
+++ b/exp1/Core/Src/main.c
@@ -56,7 +56,24 @@ void SystemClock_Config(void);
 
 /* Private user code ---------------------------------------------------------*/
 /* USER CODE BEGIN 0 */
-
+void delay_us(uint32_t nus) {
+  uint32_t ticks;
+  uint32_t told, tnow, tcnt=0;
+  uint32_t reload = SysTick->LOAD;      // LOAD的值
+  ticks = nus * SYSTICKCLK;             // 需要的节拍数
+  told = SysTick->VAL;                  // 刚进入时的计数器值
+  while (1) {
+    tnow = SysTick->VAL;
+    if (tnow != told) {
+      if (tnow < told)
+        tcnt += told - tnow;            // SYSTICK是一个递减的计数器就可以了
+      else
+        tcnt += reload - tnow + told;
+      told = tnow;
+      if (tcnt >= ticks) break;         // 事件超过/等于要延迟的时间，则退出
+    }
+  }
+}
 /* USER CODE END 0 */
 
 /**
@@ -104,10 +121,14 @@ int main(void)
     }
     if (sSysTickTimer.bTimeOk) {
       sSysTickTimer.bTimeOk = 0;
-      HAL_GPIO_TogglePin(TickClock_LED_GPIO_Port, TickClock_LED_Pin);
+      // HAL_GPIO_TogglePin(TickClock_LED_GPIO_Port, TickClock_LED_Pin);
     }
-    // HAL_GPIO_TogglePin(TickClock_LED_GPIO_Port, TickClock_LED_Pin);
-    // HAL_Delay(100);
+    HAL_GPIO_TogglePin(TickClock_LED_GPIO_Port, TickClock_LED_Pin);
+    // HAL_Delay(500);
+    for (int i = 0; i < 50000; i++) {
+      delay_us(10); // 用for循环产生10微秒
+    }
+    // delay_us(500000);
   }
   /* USER CODE END 3 */
 }