proj

ES/Lab/Lab11/PWM_Keyboard.c

@@ -1,54 +1,87 @@
 #include <LPC17xx.h>
 
+// Global variable to store PWM value
 unsigned long pwm_value = 0;
 
+// Function to initialize PWM (Pulse Width Modulation)
 void PWM_Init(void){
+    // Configure P1.20 (PWM1.2) function as PWM output (bits 21:20 = 10)
     LPC_PINCON->PINSEL3 |= 0x02 << 8;
+    // Enable power for PWM1 (bit 6)
     LPC_SC->PCONP |= 1 << 6;
+    // Set prescaler to 0 (no division)
     LPC_PWM1->PR = 0;
+    // Set timer in PWM mode (counter mode)
     LPC_PWM1->CTCR = 0;
+    // Set PWM period (MR0 determines cycle frequency)
     LPC_PWM1->MR0 = 1000;
+    // Set initial PWM duty cycle for channel 2 to 50%
     LPC_PWM1->MR2 = 500;
+    // Enable shadow latch for MR0 and MR2
     LPC_PWM1->LER = 0x05;
+    // Enable PWM output for channel 2 (bit 10)
     LPC_PWM1->PCR = 1 << 10;
+    // Enable PWM counter and PWM mode (bits 3:0 = 1001)
     LPC_PWM1->TCR = 0x09;
+    // Enable PWM1 interrupt in NVIC
     NVIC_EnableIRQ(PWM1_IRQn);
 }
 
+// Function to initialize keyboard GPIO pins
 void Keyboard_Init(void){
+    // Configure P0.0-P0.3 as GPIO (clear bits for pins 0-3 in PINSEL0)
     LPC_PINCON->PINSEL0 &= ~0x0FFF;
+    // Set P0.0-P0.3 as input (clear bits 0-3 in FIODIR)
     LPC_GPIO0->FIODIR &= ~0x0F;
 }
 
+// Simple delay function for debouncing
 void Delay(unsigned long count){
     for(unsigned long i = 0; i < count; i++);
 }
 
+// Function to read keyboard input with debouncing
 unsigned char Read_Keyboard(void){
+    // Check each of the 4 keyboard lines
     for(unsigned char i = 0; i < 4; i++){
+        // If a key is pressed (pin is low)
         if(!(LPC_GPIO0->FIOPIN & (1 << i))){
+            // Debounce delay
             Delay(500000);
+            // Check if key is still pressed
             if(!(LPC_GPIO0->FIOPIN & (1 << i))){
+                // Wait for key release
                 while(!(LPC_GPIO0->FIOPIN & (1 << i)));
+                // Debounce delay after release
                 Delay(500000);
+                // Return the key number (0-3)
                 return i;
             }
         }
     }
+    // Return 0xFF if no key pressed
     return 0xFF;
 }
 
+// Main program entry point
 int main(void){
     unsigned char key;
+    // Array of PWM values corresponding to each key
     const unsigned long pwm_values[] = {100, 250, 500, 750};
 
+    // Initialize hardware peripherals
     PWM_Init();
     Keyboard_Init();
 
+    // Main program loop
     while(1){
+        // Read keyboard input
         key = Read_Keyboard();
+        // If a valid key is pressed (0-3)
         if(key < 4){
+            // Update PWM duty cycle based on key pressed
             LPC_PWM1->MR2 = pwm_values[key];
+            // Enable latch for MR2 to update PWM output
             LPC_PWM1->LER |= 0x04;
         }
     }
@@ -56,6 +89,8 @@ int main(void){
     return 0;
 }
 
+// PWM1 interrupt handler
 void PWM1_IRQHandler(void){
+    // Clear interrupt flag for MR0 (bit 0)
     LPC_PWM1->IR |= 0x01;
 }