clock_scaling_example.c

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/* Copyright (c) 2007, Atmel Corporation All rights reserved.
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#include <avr32/io.h>
#include "board.h"
#include "pm.h"
#include "gpio.h"

#define CLOCK_DIV_ON 1
#define CLOCK_DIV_OFF 0
#define DIV_HALF 0
#define DIV_FOURTH 1

int main(void) {
        unsigned int pbasel = DIV_FOURTH;
        unsigned int pbbsel = DIV_FOURTH;
        
        // set synchronous clock source to external oscillator 0
        pm_switch_to_osc0(&AVR32_PM, FOSC0, OSC0_STARTUP);
        
        // set lower frequency on peripheral busses
        // the pm_cksel function takes care of safe clock adjustments
        pm_cksel(&AVR32_PM, CLOCK_DIV_ON, pbasel, CLOCK_DIV_ON, pbbsel,
                        CLOCK_DIV_OFF, 0);
        
        // indicate full speed with LED
        gpio_clr_gpio_pin(LED0_GPIO);
        
        while(1){
                
                // Set CPU speed according to the pressed button

                        if(gpio_get_pin_value(GPIO_PUSH_BUTTON_0) == 0) {
                                // No clock division for CPU
                                pm_cksel(&AVR32_PM, CLOCK_DIV_ON, pbasel, CLOCK_DIV_ON, pbbsel,
                                                CLOCK_DIV_OFF, 0);
                                gpio_clr_gpio_pin(LED0_GPIO);
                                gpio_set_gpio_pin(LED1_GPIO);
                                gpio_set_gpio_pin(LED2_GPIO);
                        }
                        if(gpio_get_pin_value(GPIO_PUSH_BUTTON_1) == 0){
                                // CPU speed = 1/2 * oscillator0
                                pm_cksel(&AVR32_PM, CLOCK_DIV_ON, pbasel, CLOCK_DIV_ON, pbbsel,
                                                CLOCK_DIV_ON, DIV_HALF);
                                gpio_clr_gpio_pin(LED1_GPIO);
                                gpio_set_gpio_pin(LED0_GPIO);
                                gpio_set_gpio_pin(LED2_GPIO);
                        }
                        if(gpio_get_pin_value(GPIO_PUSH_BUTTON_2) == 0){
                                // CPU speed = 1/4 * oscillator0
                                pm_cksel(&AVR32_PM, CLOCK_DIV_ON, pbasel, CLOCK_DIV_ON, pbbsel,
                                                CLOCK_DIV_ON, DIV_FOURTH);
                                gpio_clr_gpio_pin(LED2_GPIO);
                                gpio_set_gpio_pin(LED0_GPIO);
                                gpio_set_gpio_pin(LED1_GPIO);
                        }
                                
        }
        return 0;
}

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