diff --git a/ES/Lab/Lab11/PWM_Keyboard.c b/ES/Lab/Lab11/PWM_Keyboard.c
index 7e87fd4..f56277d 100644
--- a/ES/Lab/Lab11/PWM_Keyboard.c
+++ b/ES/Lab/Lab11/PWM_Keyboard.c
@@ -1,7 +1,9 @@
 #include "LPC17xx.h"
 
 volatile unsigned long int duty_cycle = 300;
-unsigned int last_key = 0xFF;
+volatile unsigned long int pwm_counter = 0;
+
+#define LED_MASK            (0xFF << 4)
 
 #define COL0                (1<<0)
 #define COL1                (1<<1)
@@ -40,8 +42,15 @@ void PWM1_IRQHandler(void)
 {
     if (LPC_PWM1->IR & (1 << 0))
     {
-        LPC_PWM1->MR4 = duty_cycle;
-        LPC_PWM1->LER = (1 << 4);
+        if(pwm_counter < duty_cycle)
+            LPC_GPIO0->FIOSET = LED_MASK;
+        else
+            LPC_GPIO0->FIOCLR = LED_MASK;
+
+        pwm_counter++;
+        if(pwm_counter >= 3000)
+            pwm_counter = 0;
+
         LPC_PWM1->IR = (1 << 0);
     }
 }
@@ -50,16 +59,18 @@ int main(void)
 {
     unsigned int col_idx;
     unsigned int read_key;
+    unsigned int last_key = 0xFF;
 
     LPC_PINCON->PINSEL0 &= ~(0xFFFF << 8);
     LPC_PINCON->PINSEL1 &= ~(0xFFFF << 14);
     LPC_PINCON->PINSEL4 &= ~(0xF << 0);
-    LPC_PINCON->PINSEL3 |= (2 << 14);
 
+    LPC_GPIO0->FIODIR |= LED_MASK;
     LPC_GPIO0->FIODIR |= COL_MASK_P0;
     LPC_GPIO2->FIODIR |= COL_MASK_P2;
     LPC_GPIO0->FIODIR &= ~ROW0;
 
+    LPC_GPIO0->FIOCLR = LED_MASK;
     LPC_GPIO2->FIOSET = COL_MASK_P2;
     LPC_GPIO0->FIOSET = COL_MASK_P0;
 
@@ -68,14 +79,11 @@ int main(void)
     LPC_PWM1->PR = 0;
 
     LPC_PWM1->MR0 = 3000;
-    LPC_PWM1->MR4 = duty_cycle;
-
     LPC_PWM1->MCR = (1 << 1) | (1 << 0);
-    LPC_PWM1->PCR = (1 << 12);
-
-    LPC_PWM1->LER = (1 << 0) | (1 << 4);
+    LPC_PWM1->LER = (1 << 0);
 
     NVIC_EnableIRQ(PWM1_IRQn);
+    NVIC_SetPriority(PWM1_IRQn, 0);
 
     LPC_PWM1->TCR = (1 << 0) | (1 << 3);