77 lines
2.6 KiB
C
77 lines
2.6 KiB
C
#include "LPC17xx.h"
|
|
|
|
// Global variables for PWM control
|
|
unsigned long int duty_cycle = 0; // Current duty cycle value (0-3000)
|
|
int direction = 1; // Direction of duty cycle change: 1=increasing, 0=decreasing
|
|
int step = 50; // Amount to change duty cycle per interrupt
|
|
|
|
// PWM1 Interrupt Service Routine
|
|
// Called when PWM match register 0 triggers an interrupt
|
|
void PWM1_IRQHandler(void)
|
|
{
|
|
// Check if interrupt flag for PWM match channel 0 is set
|
|
if (LPC_PWM1->IR & (1 << 0))
|
|
{
|
|
// Ramp up the duty cycle if direction is 1
|
|
if (direction == 1)
|
|
{
|
|
duty_cycle += step;
|
|
// Check if we've reached maximum duty cycle
|
|
if (duty_cycle >= 3000)
|
|
{
|
|
duty_cycle = 3000;
|
|
direction = 0; // Change direction to decreasing
|
|
}
|
|
}
|
|
// Ramp down the duty cycle if direction is 0
|
|
else
|
|
{
|
|
duty_cycle -= step;
|
|
// Check if we've reached minimum duty cycle
|
|
if (duty_cycle <= 0)
|
|
{
|
|
duty_cycle = 0;
|
|
direction = 1; // Change direction to increasing
|
|
}
|
|
}
|
|
|
|
// Update PWM match register 4 with new duty cycle
|
|
LPC_PWM1->MR4 = duty_cycle;
|
|
// Latch the new match value
|
|
LPC_PWM1->LER = (1 << 4);
|
|
// Clear the interrupt flag for channel 0
|
|
LPC_PWM1->IR = (1 << 0);
|
|
}
|
|
}
|
|
|
|
int main(void)
|
|
{
|
|
// Configure P2.5 as PWM1[4] output
|
|
// PINSEL3 bits 15:14 = 10 for PWM1[4] function
|
|
LPC_PINCON->PINSEL3 |= (2 << 14);
|
|
|
|
// Reset and configure PWM1 counter and prescaler
|
|
LPC_PWM1->TCR = (1 << 1); // Reset PWM counter
|
|
LPC_PWM1->CTCR = 0; // Timer mode (counter increments on PCLK)
|
|
LPC_PWM1->PR = 0; // Prescaler = 0 (no prescaling)
|
|
|
|
// Set PWM cycle period and initial duty cycle
|
|
LPC_PWM1->MR0 = 3000; // PWM period (match register 0)
|
|
LPC_PWM1->MR4 = duty_cycle; // Initial duty cycle (match register 4)
|
|
|
|
// Configure PWM interrupts and enable output
|
|
LPC_PWM1->MCR = (1 << 1) | (1 << 0); // Reset on MR0 and interrupt on MR0
|
|
LPC_PWM1->PCR = (1 << 12); // Enable PWM4 output
|
|
|
|
// Latch the match register values
|
|
LPC_PWM1->LER = (1 << 0) | (1 << 4);
|
|
|
|
// Enable PWM1 interrupt in NVIC
|
|
NVIC_EnableIRQ(PWM1_IRQn);
|
|
|
|
// Start PWM counter and enable PWM mode
|
|
LPC_PWM1->TCR = (1 << 0) | (1 << 3); // Counter enable and PWM enable
|
|
|
|
// Infinite loop - everything is handled by interrupts
|
|
while (1);
|
|
}
|