diff --git a/source/test/pwm/main.c b/source/test/pwm/main.c
index 0f7789a..225fba0 100644
--- a/source/test/pwm/main.c
+++ b/source/test/pwm/main.c
@@ -30,7 +30,8 @@ static TIM_HandleTypeDef timer_handle = {
 static TIM_IC_InitTypeDef input_capture_init = {
 		.ICPrescaler = TIM_ICPSC_DIV1,
 		.ICFilter = 0,
-		.ICPolarity = TIM_ICPOLARITY_FALLING,
+//		.ICPolarity = TIM_ICPOLARITY_FALLING,
+		.ICPolarity = TIM_ICPOLARITY_BOTHEDGE,
 		.ICSelection = TIM_ICSELECTION_INDIRECTTI,
 };
 
@@ -64,9 +65,7 @@ static const struct driver gpio_b10 = {
 		&__gpio_b10,
 };
 
-static uint32_t ch3 = 0, ch4 = 0;
-static int period = 0, pulse = 0;
-
+static int period = 0, period_start = 0, pulse = 0, pulse_start = 0;
 
 void config_input(void)
 {
@@ -77,13 +76,8 @@ void config_input(void)
 	/* cfg timer */
 	HAL_TIM_IC_Init(&timer_handle);
 	HAL_TIM_IC_ConfigChannel(&timer_handle, &input_capture_init, TIM_CHANNEL_4);
-	input_capture_init.ICPolarity = TIM_ICPOLARITY_RISING;
-	input_capture_init.ICSelection = TIM_ICSELECTION_DIRECTTI;
-	HAL_TIM_IC_ConfigChannel(&timer_handle, &input_capture_init, TIM_CHANNEL_3);
-
 	HAL_TIM_SlaveConfigSynchronization(&timer_handle, &slave_config);
 	HAL_TIM_IC_Start_IT(&timer_handle, TIM_CHANNEL_4);
-	HAL_TIM_IC_Start_IT(&timer_handle, TIM_CHANNEL_3);
 
 	HAL_NVIC_EnableIRQ(TIM2_IRQn);
 }
@@ -109,18 +103,14 @@ int main(void)
 			drv_ioctl(&pwm_3, IOCTL_PWM_SET_DUTY_CYCLE, (const void *)&duty);
 			drv_ioctl(&pwm_4, IOCTL_PWM_SET_DUTY_CYCLE, (const void *)&duty);
 			sleep_ms(100);
-			if((period >= 0) && (pulse >= 0)) {
-//				sprintf(print_buffer, "period: %u,\tpulse: %u\r\n", period, pulse);
-//				drv_write(&uart_1, print_buffer, strlen(print_buffer));
 
-				float dist = 84000.0 / pulse;
-				dist = 343.0 / dist;
-				dist /= 2.0;
-				dist *= 100; // m -> cm
-				int d = (int)dist;
-				sprintf(print_buffer, "distance: %d cm\r\n", d);
-				drv_write(&uart_1, print_buffer, strlen(print_buffer));
-			}
+			float dist = 84000.0 / pulse;
+			dist = 343.0 / dist;
+			dist /= 2.0;
+			dist *= 100; // m -> cm
+			int d = (int)dist;
+			sprintf(print_buffer, "distance: %d cm\r\n", d);
+			drv_write(&uart_1, print_buffer, strlen(print_buffer));
 		}
 		for(unsigned int duty = 98; duty > 0; duty--) {
 			drv_ioctl(&pwm_1, IOCTL_PWM_SET_DUTY_CYCLE, (const void *)&duty);
@@ -128,18 +118,14 @@ int main(void)
 			drv_ioctl(&pwm_3, IOCTL_PWM_SET_DUTY_CYCLE, (const void *)&duty);
 			drv_ioctl(&pwm_4, IOCTL_PWM_SET_DUTY_CYCLE, (const void *)&duty);
 			sleep_ms(100);
-			if((period >= 0) && (pulse >= 0)) {
-//				sprintf(print_buffer, "period: %u,\tpulse: %u\r\n", period, pulse);
-//				drv_write(&uart_1, print_buffer, strlen(print_buffer));
 
-				float dist = 84000.0 / pulse;
-				dist = 343.0 / dist;
-				dist /= 2.0;
-				dist *= 100; // m -> cm
-				int d = (int)dist;
-				sprintf(print_buffer, "distance: %d cm\r\n", d);
-				drv_write(&uart_1, print_buffer, strlen(print_buffer));
-			}
+			float dist = 84000.0 / pulse;
+			dist = 343.0 / dist;
+			dist /= 2.0;
+			dist *= 100; // m -> cm
+			int d = (int)dist;
+			sprintf(print_buffer, "distance: %d cm\r\n", d);
+			drv_write(&uart_1, print_buffer, strlen(print_buffer));
 		}
 	}
 
@@ -151,51 +137,27 @@ void TIM2_IRQHandler(void)
 {
 	enter_isr();
 	TIM_HandleTypeDef *htim = &timer_handle;
-	uint32_t tmpreg = 0U;
 
-	if(__HAL_TIM_GET_FLAG(htim, TIM_FLAG_CC1) != RESET) {
-		if(__HAL_TIM_GET_IT_SOURCE(htim, TIM_IT_CC1) !=RESET) {
-			__HAL_TIM_CLEAR_IT(htim, TIM_IT_CC1);
-			/* Input capture event */
-			if((htim->Instance->CCMR1 & TIM_CCMR1_CC1S) != 0x00U) {
-				tmpreg = htim->Instance->CCR1;
-			}
-		}
-	}
-	/* Capture compare 2 event */
-	if(__HAL_TIM_GET_FLAG(htim, TIM_FLAG_CC2) != RESET) {
-		if(__HAL_TIM_GET_IT_SOURCE(htim, TIM_IT_CC2) !=RESET) {
-			__HAL_TIM_CLEAR_IT(htim, TIM_IT_CC2);
-			/* Input capture event */
-			if((htim->Instance->CCMR1 & TIM_CCMR1_CC2S) != 0x00U) {
-				tmpreg = htim->Instance->CCR2;
-			}
-		}
-	}
-	/* Capture compare 3 event */
-	if(__HAL_TIM_GET_FLAG(htim, TIM_FLAG_CC3) != RESET) {
-		if(__HAL_TIM_GET_IT_SOURCE(htim, TIM_IT_CC3) !=RESET) {
-			__HAL_TIM_CLEAR_IT(htim, TIM_IT_CC3);
-			/* Input capture event */
-			if((htim->Instance->CCMR2 & TIM_CCMR2_CC3S) != 0x00U) {
-				ch3 = htim->Instance->CCR3;
-			}
-		}
-	}
 	/* Capture compare 4 event */
 	if(__HAL_TIM_GET_FLAG(htim, TIM_FLAG_CC4) != RESET) {
 		if(__HAL_TIM_GET_IT_SOURCE(htim, TIM_IT_CC4) !=RESET) {
 			__HAL_TIM_CLEAR_IT(htim, TIM_IT_CC4);
 			/* Input capture event */
 			if((htim->Instance->CCMR2 & TIM_CCMR2_CC4S) != 0x00U) {
-				uint32_t ch4_old = ch4;
-				ch4 = htim->Instance->CCR4;
-				period = ch4 - ch4_old;
-				pulse = ch4 - ch3;
+				uint32_t ch4 = htim->Instance->CCR4;
+				if(GPIO_PIN_SET == HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_10)) {
+					if(ch4 > period_start)
+						period = ch4 - period_start;
+					period_start = ch4;
+					pulse_start = ch4;
+				}
+				else {
+					if(ch4 > pulse_start)
+						pulse = ch4 - pulse_start;
+				}
 			}
 		}
 	}
-	tmpreg = tmpreg;
 
 	exit_isr();
 }