// ping.c - this code will set up and run the PING ultrasound sensor
// This code will not compute the distance
// If the timer overflows, than nothing was seen in front of the sensor.                                                                    

#define PING_PORT		p9_4
#define PING_PORT_DIR	pd9_4
#define B4TIME_CONFIG 0x4A  

unsigned int Ping_Width=0xFFFF;
char ping_done=0;


void Ping_init(void)
{
	DISABLE_IRQ			
	  	tb4ic = 0x03;   
	ENABLE_IRQ	
}


#pragma INTERRUPT ping_irq
void ping_irq()
{
	if (mr3_tb4mr == 1)
	{		// check for timer overflow
		tb4s=0;
		ping_done=1;
		Ping_Width= 0;
    		return;	// data invalid, so exit routine
  	}
	/* check if high or low pulse width was measured */
 	if (PING_PORT == 1)
	{
		// this is the low width
  		//Ping_Width = tb4;       	// if input is now hi, low width measured
	}
 	else
	{
		Ping_Width = tb4;		// input is now low, high width measured
	}
	// set ping is done flag
	ping_done=1;
	tb4s=0;
}


// send out a ping
void Ping()
{
		int lp=0;
		ping_done=0;
		// ok this is crazy but you can only write to this Port DIR after 
		// PRC Reg Command
		prc2 = 1;
		// change port to output
		PING_PORT_DIR = 1;
		// send output wave
		PING_PORT = 1;  // send out a pulse
		// loop to keep it high for a bit
		for(lp=0;lp<50;lp++)
		{
		}
		// stop the output wave
		PING_PORT = 0;  // end the pulse
		// change port back to input
		prc2 = 1;
		PING_PORT_DIR = 0;	// set port direction of Ping to input
		// start TimerB PWM width measure
		tb4=0;
		tb4mr = B4TIME_CONFIG;
		tb4s = 1; // turn on the timer
}

char  Ping_Done()
{
	return ping_done;
}

int Get_Ping_Width()
{
	return Ping_Width;
}