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