/**
 * I2C SRF10 or SRF08 Devantech Ultrasonic Ranger Finder 
 * by Nicholas Zambetti <http://www.zambetti.com>
 * and James Tichenor <http://www.jamestichenor.net> 
 * 
 * Demonstrates use of the Wire library reading data from the 
 * Devantech Utrasonic Rangers SFR08 and SFR10
 */

#include <Wire.h>

void setup()
{
  Wire.begin();        // join i2c bus (address optional for master)
  Serial.begin(9600);  // start serial communication at 9600bps
}

int reading = 0;

void loop()
{
  // step 1: instruct sensor to read echoes
  Wire.beginTransmission(112);  // transmit to device #112 (0x70)
                                // the address specified in the datasheet is 224 (0xE0)
                                // but i2c adressing uses the high 7 bits so it's 112
  Wire.send(0x00);              // sets register pointer to the command register (0x00)  
  Wire.send(0x50);              // command sensor to measure in "inches" (0x50) 
                                // use 0x51 for centimeters
                                // use 0x52 for ping microseconds
  Wire.endTransmission();       // stop transmitting

  // step 2: wait for readings to happen
  delay(70);                    // datasheet suggests at least 65 milliseconds

  // step 3: instruct sensor to return a particular echo reading
  Wire.beginTransmission(112);  // transmit to device #112
  Wire.send(0x02);              // sets register pointer to echo #1 register (0x02)
  Wire.endTransmission();       // stop transmitting

  // step 4: request reading from sensor
  Wire.requestFrom(112, 2);     // request 2 bytes from slave device #112

  // step 5: receive reading from sensor
  if(2 <= Wire.available())     // if two bytes were received
  {
    reading = Wire.receive();   // receive high byte (overwrites previous reading)
    reading = reading << 8;     // shift high byte to be high 8 bits
    reading |= Wire.receive();  // receive low byte as lower 8 bits
    Serial.println(reading);    // print the reading
  }

  delay(250);                   // wait a bit since people have to read the output :)
}


/*

// The following code changes the address of a Devantech Ultrasonic Range Finder (SRF10 or SRF08)
// usage: changeAddress(0x70, 0xE6);

void changeAddress(byte oldAddress, byte newAddress)
{
  Wire.beginTransmission(oldAddress);
  Wire.send(0x00);
  Wire.send(0xA0);
  Wire.endTransmission();

  Wire.beginTransmission(oldAddress);
  Wire.send(0x00);
  Wire.send(0xAA);
  Wire.endTransmission();

  Wire.beginTransmission(oldAddress);
  Wire.send(0x00);
  Wire.send(0xA5);
  Wire.endTransmission();

  Wire.beginTransmission(oldAddress);
  Wire.send(0x00);
  Wire.send(newAddress);
  Wire.endTransmission();
}

*/
