Basic Tilt Sensor Tutorial

The Software
           There are two main portions of code that we are concerned with:
    -LED Output Code
    -Tilt Sensor Polling



           The whole firmware program for this project can be found below. It consists of a few variable setups and then 4 for loops that make a single LED move back and forth across the LED bar. Everytime the LED moves the tilt sensor is checked to see if it has changed state. If a change is detected the firmware pauses in a forever while loop, until the tilt sensor returns to it's previous logic 0 state.

ASCII to Numbers/Letters

#include «p18f452.h»
#include «delays.h»

#pragma config OSC = HS
#pragma config LVP = OFF
#pragma config WDT = OFF

void main(void){

unsigned int count=0;
unsigned int led_out=0xFE;

//PORTA Digital I/O
ADCON1 = 0b00000110;

//PORTA Used For Inputs
TRISA = 0xFF;

//PORTD Used For Outputs
TRISD = 0x00;
PORTD = 0xFF;

	while(1){
		for(count=0;count<7;count++){
			led_out = (led_out<<1);
			PORTD = led_out;
			Delay10KTCYx(40);
			while(PORTAbits.RA0 == 1);	
		}
		for(count=0;count<7;count++){
			led_out = (led_out<<1)|0x01;
			PORTD = led_out;
			Delay10KTCYx(40);
			while(PORTAbits.RA0 == 1);
		}
		for(count=0;count<7;count++){
			led_out = (led_out>>1);
			PORTD = led_out;
			Delay10KTCYx(40);
			while(PORTAbits.RA0 == 1);
		}
		for(count=0;count<7;count++){
			led_out = (led_out>>1)|0x80;
			PORTD = led_out;
			Delay10KTCYx(40);
			while(PORTAbits.RA0 == 1);
		}
	}
}

           One small thing to notice, since the LEDs only turn on when PORTD's bits are set to logic 0, a single logic 0 is moving back and forth across PORTD's 8 bits. this is seemingly backwards from the idea that a logic 1 should mean: LED on, but it's just how I designed the system in the schematic so that power consumption came from the 7805 regulator and not through the PIC's I/O ports.