/*
 * Title: Ultrasound
 * 
 * Author: Blake C. Sutton
 * 
 * This is a set of functions used to test and read input from
 * a SRF04 ultrasound ranger connected to a port on the Mavric IIB.
 * It will have functions to tell the SRF04 to send a pulse out,
 * read the data back (by counting the cycles the SRF04 output pin
 * is high ), and be able to display this value on the LCD
 *
 * Pulse Trigger input (to SRF04) : Port D, pin 0 
 * Echo output (to Mavric II) : Port D, pin 1
 */

#ifndef __Ultrasound__
#define __Ultrasound__

#include "LCD_Routines.h"

#define PULSE_TRIGGER (0x01)
#define ECHO_OUTPUT   (0x02)

//Length of array of sonar readings
#define ARRAY_LENGTH    2

//Constants defining thresholds of closeness to an object
#define VERY_NEAR		0x00A5
#define NEAR			0x00A8

/* 16-bit unsigned integer used for ultrasound timing */
volatile uint16_t ultrasound_count;

/* Array holding the last ARRAY_LENGTH readings from the SRF04 */
volatile uint16_t sonar_readings [ARRAY_LENGTH];
volatile uint8_t sonar_readings_ct;

//Internal use only
void init_ultrasound_timer(void);

//Use this with other port initializing functions
void init_ultrasound_port(void);

//Internal use only - consider modifying internal 1ms delay
void send_pulse(void);

//Call this in the main loop to keep updating the sonar with
//pings and readings back.  Results are added to the sonar_readings
//array above.
void update_sonar(void);

#endif