clock_scaling_example.c File Reference

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Detailed Description

Clock scaling example for the AVR32 UC3.

• Compiler: IAR EWAVR32 and GNU GCC for AVR32
• Supported devices: All AVR32 devices with a power manager.
• AppNote:

Author:

Atmel Corporation: http://www.atmel.com
Support and FAQ: http://support.atmel.no/

Definition in file clock_scaling_example.c.

#include <avr32/io.h>
#include "board.h"
#include "pm.h"
#include "gpio.h"

Include dependency graph for clock_scaling_example.c:

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Defines
#define	CLOCK_DIV_OFF   0
#define	CLOCK_DIV_ON   1
#define	DIV_FOURTH   1
#define	DIV_HALF   0
Functions
int	main (void)
	main function : set clock scaling according to pressed button.

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Define Documentation

#define CLOCK_DIV_OFF   0

Definition at line 94 of file clock_scaling_example.c.

#define CLOCK_DIV_ON   1

Introduction

This example demonstrates the CPU (and HSB) frequency scaling feature of the AVR32. This can be done on-the-fly. Operating mode: Press button 0 to set CPU (HSB) clock to full speed (Oscillator 0 = 12MHz). Press button 1 to set CPU (HSB) clock to half speed (6MHz). Press button 2 to set CPU (HSB) clock to forth speed (3MHz).

Depending on the current CPU speed a LED is turned on. LED0 = full speed LED1 = half speed LED2 = forth speed

NOTE: If the user of this software intends to change division factors for the clocks or use the PLL take following rules into account:

• CPU(HSB) clock must always be higher than the peripheral bus clocks

Flash wait states must be added when high frequencies are used

Main Files

• pm.c: power manager driver;
• pm.h: power manager driver header file;
• gpio.c: gpio controller driver;
• gpio.h: gpio controller driver header file;
• clock_scaling_example.c: CPU frequency scaling example application.

Compilation Information

This software is written for GNU GCC for AVR32 and for IAR Embedded Workbench for Atmel AVR32. Other compilers may or may not work.

Device Information

All AVR32 devices with GPIO controller and power manager.

Configuration Information

This example has been tested with the following configuration:

• EVK1100 evaluation kit;
• CPU clock: 12 MHz from oscillator 0 at full speed, 6 MHz half speed and 3 MHz at forth speed;

Contact Information

For further information, visit Atmel AVR32.
Support and FAQ: http://support.atmel.no/

Definition at line 93 of file clock_scaling_example.c.

#define DIV_FOURTH   1

Definition at line 96 of file clock_scaling_example.c.

#define DIV_HALF   0

Definition at line 95 of file clock_scaling_example.c.

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Function Documentation

int main

(

void

)

main function : set clock scaling according to pressed button.

Definition at line 101 of file clock_scaling_example.c.

References CLOCK_DIV_OFF, CLOCK_DIV_ON, DIV_FOURTH, DIV_HALF, FOSC0, gpio_clr_gpio_pin(), gpio_get_pin_value(), GPIO_PUSH_BUTTON_0, GPIO_PUSH_BUTTON_1, GPIO_PUSH_BUTTON_2, gpio_set_gpio_pin(), LED0_GPIO, LED1_GPIO, LED2_GPIO, OSC0_STARTUP, pm_cksel(), and pm_switch_to_osc0().

               {
        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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