diff --git a/source/test/pwm/main.c b/source/test/pwm/main.c
index 9ad07bd..b9150fa 100644
--- a/source/test/pwm/main.c
+++ b/source/test/pwm/main.c
@@ -74,11 +74,16 @@ static void th_func(void *arg)
 	unsigned int duty = 0;
 	pwm_open(&pwm_ch4);
 	while(1) {
-		pwm_set_duty_cycle(&pwm_ch4, duty);
-		sleep_ms(100);
-		duty++;
-		if(duty > 100)
-			duty = 0;
+		while(duty < 100) {
+			pwm_set_duty_cycle(&pwm_ch4, duty);
+			sleep_ms(10);
+			duty++;
+		}
+		while(duty > 0) {
+			pwm_set_duty_cycle(&pwm_ch4, duty);
+			sleep_ms(10);
+			duty--;
+		}
 	}
 }