“code_art_bcm_10.c” Respostas de código

code_art_bcm_10.c

/*
Copyright (c) 2008, Nigel Batten.
Contactable at <firstname>.<lastname>@mail.com

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A demonstration of binary code modulation LED dimming.
Nigel Batten, 2008

Written for a 'factory setting' Mega8 (highbyte: 0xd9, lowbyte:  0xe1)
e.g. running on 1Mhz internal RC oscillator.

Outputs a 'sweep' pattern on LEDs connected to port D.
Could be extended to handle more ports.
Could be modified to mask off pins used for other purposes.

*/

#include <avr/io.h>
#include <avr/interrupt.h>

// define the processor speed if it's not been defined at the compilers command line.
#ifndef F_CPU
#define F_CPU 1000000
#endif

volatile uint8_t g_timeslice[8] ; // one byte for each bit-position being displayed on a port.
volatile uint8_t g_tick = 0;
volatile uint8_t g_bitpos = 0; // which bit position is currently being shown

void led_init( void ) ;
void led_encode_timeslices( uint8_t a[] );


__attribute((OS_main)) int main(void)
{
uint8_t brightness[8]; // brightness for each LED on port D.

	led_init();
	led_encode_timeslices( brightness ) ;
	sei();


// now a (simple) demonstration...
// In the real-world, you'd probably want to decouple the
// animation speed from the LED flicker-rate.
uint8_t slowtick = 30;
uint8_t position = 0 ;
    while(1)
    {
		while(g_tick==0){ /*wait for g_tick to be non-zero*/ }
		g_tick = 0 ; //consume the tick
		// make each of the LEDs slightly dimmer...
		for ( uint8_t index = 0 ; index < 8 ; index++ )
		{
			if (brightness[ index ] > 0) brightness[ index ]-- ;
		}
		// once every 50 ticks, advance the head of the sweep...
		slowtick-- ;
		if (slowtick==0)
		{
			slowtick = 30;
			position++ ;
			position &= 7 ;
			brightness[ position ] = 100 ;
		}
		// and now re-encode all the timeslices...
		led_encode_timeslices( brightness ) ;
	}
    return(0);
}


// simple initialisation of the port and timer
void led_init( void )
{
	PORTD = 0x00 ; // All outputs to 0.
	DDRD = 0xff ; // All outputs.
	
	TCCR2 |= (1<<WGM21) ; // set the timer to CTC mode.
	TCCR2 |= ((1<<CS21)|(1<<CS20)) ; // use clock/32 tickrate
	g_bitpos = 0 ;
	OCR2 = 1 ; // initial delay.
	TIMSK |= (1 << OCIE2) ; // Enable the Compare Match interrupt
}


// encode an array of 8 LED brightness bytes into the pattern
// to be shown on the port for each of the 8 timeslices.
void led_encode_timeslices( uint8_t intensity[] )
{
	uint8_t portbits = 0;
	uint8_t bitvalue ;
	
	for ( uint8_t bitpos = 0 ; bitpos < 8 ; bitpos++ )
	{
		portbits = 0;
		bitvalue = 1 ;
		for ( uint8_t ledpos = 0 ; ledpos < 8 ; ledpos++ )
		{
			if (intensity[ ledpos ] & (1 << bitpos)) portbits |= bitvalue ;
			bitvalue = bitvalue << 1 ;
		}
		g_timeslice[ bitpos ] = portbits ;
	}
}

// Timer interrupt handler - called once per bit position.
ISR( TIMER2_COMP_vect )
{
	g_bitpos ++ ;
	g_bitpos &= 7;
	PORTD = g_timeslice[ g_bitpos ] ;
	// now set the delay...
	TCNT2 = 0;
	OCR2 <<= 1 ;
	if (g_bitpos == 0) OCR2 = 1 ; // reset the compare match value.
	if (g_bitpos == 7) g_tick = 1 ; // give the main loop a kick.
}