main.c

#include "lm4f120h5qr.h"
#include "inc/hw_memmap.h"
#include "inc/hw_types.h"
#include "driverlib/i2c.h"
#include "driverlib/debug.h"
#include "driverlib/gpio.h"
#include "driverlib/pin_map.h"
#include "I2C_Stellaris_API.h"
#include "utils/uartstdio.h"
#include "driverlib/sysctl.h"

unsigned long srf02datalow=0;
unsigned long srf02datahigh=0;

void main(void) {

  SysCtlClockSet(SYSCTL_SYSDIV_5|SYSCTL_USE_PLL|SYSCTL_XTAL_16MHZ|SYSCTL_OSC_MAIN);	// 40MHz system clock

	SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOF);  										// enable clock for peripheral (PORTF)

	GPIOPinTypeGPIOOutput(GPIO_PORTF_BASE, GPIO_PIN_1|GPIO_PIN_2|GPIO_PIN_3);			// config PF1(red) 2(blue) 3(green) as output.

	I2CSetup(I2C3_MASTER_BASE,false); 													// false = 100KHz , true = 400KHz



	while(1)
	{

		I2CRegWrite(I2C3_MASTER_BASE, 0xF0,0x00,0x51); 									// slave address of SRF02 is 0xE0 / 0xF0 is the address right shifted by 1 bit (7bit)
		
		srf02datalow=I2CRegRead(I2C3_MASTER_BASE,0xF0,0x03);  							// reading from register 3 gives Low Byte of ranging

		if	(srf02datalow<0x1E){
			SysCtlDelay(4000000);
			GPIOPinWrite (GPIO_PORTF_BASE, GPIO_PIN_1|GPIO_PIN_2|GPIO_PIN_3, 0x02);  // switch on red at 0x1E (30cms)

		}

		else {
			SysCtlDelay(4000000);
			GPIOPinWrite (GPIO_PORTF_BASE, GPIO_PIN_1|GPIO_PIN_2|GPIO_PIN_3, 0x08); // switch on green

		}


	};
}