AVR Freaks

This is the UC3B0512 MCU. The logic that I want to make is to oscillate duty cycle between 0 and DUTY_CYCLE with the time split of 1ms. That's why I use a delay function inside the ISR.

/**
 * \file
 *
 * \brief Empty user application template
 *
 */

/**
 * \mainpage User Application template doxygen documentation
 *
 * \par Empty user application template
 *
 * Bare minimum empty user application template
 *
 * \par Content
 *
 * -# Include the ASF header files (through asf.h)
 * -# "Insert system clock initialization code here" comment
 * -# Minimal main function that starts with a call to board_init()
 * -# "Insert application code here" comment
 *
 */

/*
 * Include header files for all drivers that have been imported from
 * Atmel Software Framework (ASF).
 */
/*
 * Support and FAQ: visit <a href="http://www.atmel.com/design-support/">Atmel Support</a>
 */
#include <asf.h>
#define  DUTY_CYCLE 1000

volatile avr32_pwm_t *pwm = &AVR32_PWM;

__attribute__((__interrupt__))
void pwm_handler()
{
	AVR32_PWM.isr;   //may not seem valid
	if (pwm->channel[0].cdty == 0)
		{
			pwm->channel[0].cdty+=1;
			pwm->channel[1].cdty+=1;
			pwm->channel[2].cdty+=1;
			pwm->channel[6].cdty+=1;
		} 
		else if (pwm->channel[0].cdty < DUTY_CYCLE) //changed
		{
			pwm->channel[0].cdty+=1;
			pwm->channel[1].cdty+=1;
			pwm->channel[2].cdty+=1;
			pwm->channel[6].cdty+=1;
		}
		else
		{
			pwm->channel[0].cdty-=1;
			pwm->channel[1].cdty-=1;
			pwm->channel[2].cdty-=1;
			pwm->channel[6].cdty-=1;
		}
}

int main (void)
{
	/* Insert system clock initialization code here (sysclk_init()). */
	
	sysclk_init();
	
	delay_init(16000000);
	
	/* PWM controller configuration. */
	
	pwm_opt_t pwm_opt =
		{
			.diva = AVR32_PWM_DIVA_CLK_OFF,
			.divb = AVR32_PWM_DIVB_CLK_OFF,
			.prea = AVR32_PWM_PREA_MCK,
			.preb = AVR32_PWM_PREB_MCK
		};

	/* PWM channel configuration structure. */
	avr32_pwm_channel_t pwm_channel = { .ccnt = 0 };
	
	/* With these settings, the output waveform period will be:
	 * (115200/256)/20 == 22.5Hz == (MCK/prescaler)/period, with
	 * MCK == 115200Hz, prescaler == 256, period == 20. */
	pwm_channel.cdty = 0; /* Channel duty cycle, should be < CPRD. */
	pwm_channel.cprd = DUTY_CYCLE; /* Channel period. */
	pwm_channel.cupd = 0; /* Channel update is not used here. */
	pwm_channel.CMR.calg = PWM_MODE_LEFT_ALIGNED; /* Channel mode. */
	pwm_channel.CMR.cpol = PWM_POLARITY_LOW;      /* Channel polarity. */
	pwm_channel.CMR.cpd = PWM_UPDATE_DUTY;        /* Not used the first time. */
	pwm_channel.CMR.cpre = AVR32_PWM_CPRE_MCK_DIV_8; /* Channel prescaler. */	
	
	static const gpio_map_t PWM_GPIO_MAP =
	{
		{7, 0},
		{8, 0},
		{21,0},
		{22,0}
	};
	
	gpio_enable_module(PWM_GPIO_MAP, sizeof(PWM_GPIO_MAP)/sizeof(PWM_GPIO_MAP[0]) );
	
	/* Initialize the PWM module. */
	pwm_init(&pwm_opt);
	
	pwm_channel_init(0,&pwm_channel);
	pwm_channel_init(1,&pwm_channel);
	pwm_channel_init(2,&pwm_channel);
	pwm_channel_init(6,&pwm_channel);
	
	INTC_init_interrupts();

	// Register the EIC interrupt handlers to the interrupt controller.
	INTC_register_interrupt(&pwm_handler,
			AVR32_PWM_IRQ, AVR32_INTC_INT1);
	
	pwm->ier = 0x47;
	
	pwm_start_channels(0x47);

	cpu_irq_enable();
	/* Insert application code here, after the board has been initialized. */
	
	while(1)
	{
		delay_s(1);   //delay not in ISR :)
		pwm->ier =0x47;  //may seem not valid..
	}
}

It really does the oscillation of the brightness. However, it seems a bit strange: the LEDs blink in high brightness first and then blink in the low one after a while... (I think that 1000 is enough for the period to not form the blink).