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/*
This code receives input from the SRF02 ultrasonic and maps the values to RGB outputs to a tri-colour LED.
*/

#include <Wire.h>
int redPin   = 3;   // Red LED,   connected to digital pin 9
int greenPin = 6;  // Green LED, connected to digital pin 10
int bluePin  = 5;  // Blue LED,  connected to digital pin 11

int redVal   = 1; // Variables to store the values to send to the pins
int greenVal = 1;   // Initial values are Red full, Green and Blue off
int blueVal  = 255;

// the commands needed for the SRF sensors:
#define sensorAddress 0x70
//#define readInches 0x50
//#define readCentimeters 0x51
#define readMicroseconds 0x52
// this is the memory register in the sensor that contains the result:
#define resultRegister 0x02

void setup() {
  pinMode(redPin,   OUTPUT);
  pinMode(greenPin, OUTPUT);
  pinMode(bluePin,  OUTPUT);
  analogWrite(redPin,   redVal);   // Write current values to LED pins
  analogWrite(greenPin, greenVal);
  analogWrite(bluePin,  blueVal);
  Wire.begin();

  // open the serial port:

  Serial.begin(9600);

}

void loop()

{

  // send the command to read the result in inches:

  sendCommand(sensorAddress, readMicroseconds);
  // wait at least 70 milliseconds for a result:
  delay(100);
  // set the register that you want to reas the result from:
  setRegister(sensorAddress, resultRegister);
  int sensorReading = readData(sensorAddress, 2);

  //sensorReading = constrain(sensorReading,0,180);
  blueVal  = constrain(map(sensorReading, 800, 2000, 0, 250),0,255);
  redVal   = constrain(map(blueVal, 0, 255, 255, 0),0,255);
  greenVal = 1;   // Initial values are Red full, Green and Blue off

  analogWrite(redPin,   redVal);   // Write current values to LED pins
  analogWrite(greenPin, greenVal);
  analogWrite(bluePin,  blueVal);  

  Serial.print("distance: ");
  Serial.print(sensorReading);
  Serial.print("  mapval: ");
  Serial.print(redVal);
  Serial.print("\n");
  delay(250);
}

/*

  SendCommand() sends commands in the format that the SRF sensors expect

 */

void sendCommand (int address, int command) {

  // start I2C transmission:

  Wire.beginTransmission(address);

  // send command:

  Wire.send(0x00);

  Wire.send(command);

  // end I2C transmission:

  Wire.endTransmission();

}

/*

  setRegister() tells the SRF sensor to change the address pointer position

 */

void setRegister(int address, int thisRegister) {

  // start I2C transmission:

  Wire.beginTransmission(address);

  // send address to read from:

  Wire.send(thisRegister);

  // end I2C transmission:

  Wire.endTransmission();

}

/*

readData() returns a result from the SRF sensor

 */

int readData(int address, int numBytes) {

  int result = 0;        // the result is two bytes long

// send I2C request for data:

  Wire.requestFrom(address, numBytes);

  // wait for two bytes to return:

  while (Wire.available() < 2 )   {

    // wait for result

  }

  // read the two bytes, and combine them into one int:

  result = Wire.receive() * 256;

  result = result + Wire.receive();

  // return the result:

  return result;

}

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