/*
This sketch runs on an ATtiny85 connected to an Arduino running w13_satshakit_master.ino
The data received is from a HC-SR04 sensor
 */
 
#include <SoftwareSerial.h>
#include <TinyWireS.h>              // Requires fork by Rambo with onRequest support

const int I2CSlaveAddress = 7;

const int RX = 1; // NO RX for Sonar application
const int TX = 2; // TX (data sent by the ATTiny85)

SoftwareSerial serial(RX, TX);//rx pin of ftdi header as receiver and mosi as tx
const int trigPin = A3;  // defines pins numbers
const int echoPin = A2;  // defines pins numbers

long duration;  // defines variables
int distance;   // defines variables

#define MAX_DISTANCE 200 // Maximum distance we want to ping for (in centimeters). Maximum sensor distance is rated at 400-500cm.

void setup() 
{
    
  pinMode(trigPin, OUTPUT); // Sets the trigPin as an Output
  pinMode(echoPin, INPUT);  // Sets the echoPin as an Input
  pinMode(TX,OUTPUT);       // TX
  serial.begin(9600);       // Starts the serial communication
  
  delay(100);

  TinyWireS.begin(I2CSlaveAddress);      // Begin I2C Communication
  TinyWireS.onRequest(transmit);         // When requested, call function transmit()
}

void loop()
{
//  serial.println("Hello");
  digitalWrite(trigPin, 0);// Clears the trigPin
  delayMicroseconds(2000);
  digitalWrite(trigPin, 1);
  delayMicroseconds(5); // Sets the trigPin on HIGH state for 5 micro seconds
  digitalWrite(trigPin, 0);
  duration = pulseIn(echoPin, 1); // Reads the echoPin, returns the sound wave travel time in microseconds
  distance = duration * 0.034 / 2; // Calculating the distance
  
  if (distance > MAX_DISTANCE) {
    serial.println("out of range");
  }
  else {
    serial.print("Distance: "); // Prints the distance on the Serial Monitor
    serial.print(distance);// Prints the distance on the Serial Monitor
    serial.println(" Cm");// Prints the distance on the Serial Monitor
  } 
  delay(2000);
 }

 void transmit()
{
  TinyWireS.send(distance);                 // Send last recorded distance for current sensor
}