/*
  Sketch to read level of water in a round tank and  then send data back to controller
  uses MySensors V2 .

  Libraries used
  MySensors          https://www.mysensors.org/
  NewPing            https://bitbucket.org/teckel12/arduino-new-ping/wiki/Home
  SPI                 installed with arduino IDE

*/

// Enable debug prints to serial monitor
#define MY_DEBUG

// Enable and select radio type attached
#define MY_RADIO_NRF24
// Enabled repeater feature for this node
//#define MY_REPEATER_FEATURE

//#define MY_RF24_CHANNEL 84    // channel of nrf network

#include <MySensors.h>
#include <SPI.h>
#include <NewPing.h>

#define MY_NODE_ID 3    // comment out this line if you use dynamic id's
#define CHILD_ID_WATER 1
#define CHILD_ID_PERCENT 2


// newping settings
#define TRIGGER_PIN  6                  // Arduino pin 6 connected to trigger pin on the ultrasonic sensor.
#define ECHO_PIN     7                  // Arduino pin 7 connected to echo pin on the ultrasonic sensor.
#define MAX_DISTANCE 240                // Maximum distance we want to ping for (in centimeters). you should set this to be 
// a bit more than fullHeight + sensHeight.

/*------change these to suit your tank setup-----*/
const int tankRad = 170;                // Radius of tank in cm
const int fullHeight = 198;             // Height of water when tank full in cm
const int sensHeight = 30;              // height of sensor above full water mark in cm
const int outletHeight = 7;             // height of water when tank reading will show empty in cm
/*----------------------------------------------*/

int BATTERY_SENSE_PIN = A0;             // select the input pin for the battery sense point
int oldBatteryPcnt = 0;
unsigned long lastSent;
unsigned long heartbeatDelay = 15;     // how often the heartbeat will be sent, in minutes
//unsigned long lastHeartbeat = millis(); // holder for last time heartbeat was sent
uint32_t SLEEP_TIME = 10000;           // 900000=15 mins sleep time between reads (seconds * 1000 milliseconds)
unsigned long pingHeight;               // holds total height from ultrasonic sender to current water height
unsigned int waterAvail;                // holds current water available in litres

byte oldWaterPercent;
byte waterPercent = 0 ;                 // used to hold the tank water level percentage

// NewPing setup of pins and maximum distance.
NewPing sonar(TRIGGER_PIN, ECHO_PIN, MAX_DISTANCE);

MyMessage msgVolume(CHILD_ID_WATER, V_LEVEL);              // water available in litres
MyMessage msgPercent(CHILD_ID_PERCENT, V_LEVEL);           // water percentsge available

void setup() {

  pinMode(5, OUTPUT);
  analogReference(INTERNAL);
}

void presentation()  {
  // Send the sketch version information to the gateway and Controller
  sendSketchInfo("Tank Level", "1.4");

  // Register all sensors to gateway (they will be created as child devices)
  present(CHILD_ID_WATER, S_DUST, "Water Available");
  present(CHILD_ID_PERCENT, S_DUST, "Water Percentage Available");
}


void loop()
{
// get the battery Voltage
int sensorValue = analogRead(BATTERY_SENSE_PIN);
#ifdef MY_DEBUG
Serial.println(sensorValue);
#endif

// 1M, 470K divider across battery and using internal ADC ref of 1.1V
// Sense point is bypassed with 0.1 uF cap to reduce noise at that point
// ((2.2e6+330e3)/330e3)*1.1 = Vmax = 8.4 Volts
// 8.4/1023 = Volts per bit = 0.001075275

int batteryPcnt = sensorValue / 10;

#ifdef MY_DEBUG
//float batteryV  = sensorValue * 0.001075275;
float batteryV = sensorValue * 9.17 / 1023;

Serial.print("Battery Voltage: ");
Serial.print(batteryV);
Serial.println(" V");

Serial.print("Battery percent: ");
Serial.print(batteryPcnt);
Serial.println(" %");
#endif

if (oldBatteryPcnt != batteryPcnt) {
  // Power up radio after sleep
  sendBatteryLevel(batteryPcnt);
  oldBatteryPcnt = batteryPcnt;
}
{
  Serial.println("Waking out of sleep");
  digitalWrite(5, HIGH);
  Serial.println("Ultrasonic module ON");
  delay (1000);

  data_calc();      // perform calculations to get water remaining etc.


  if (oldWaterPercent != waterPercent) {        //check to see if new water data is available
    send(msgVolume.set(waterAvail));
    send(msgPercent.set(waterPercent));
    oldWaterPercent = waterPercent;
    lastSent = millis();
  }

  heartbeatCheck();                                    // call heartbeat function
  digitalWrite(5, LOW);
  Serial.println("Ultrasonic module OFF");

  Serial.println("Entering Sleep");
  sleep(SLEEP_TIME);

}
}
/*-------------------------start of functions-------------------*/

void heartbeatCheck() {
  unsigned long millisNow = millis();           // get the current time
  if ((millisNow - lastSent) > (heartbeatDelay * 60000)) {
    send(msgVolume.set(waterAvail));
    send(msgPercent.set(waterPercent));
    lastSent = millisNow;
  }

  /*if ((millisNow - lastHeartbeat) > (heartbeatDelay*60000)) {
    sendHeartbeat();
    wait(5);
    // sendBatteryLevel(100);
    lastHeartbeat = millis();
    #ifdef MY_DEBUG
      Serial.println("Heartbeat Sent" );
    #endif
    } */
}

void data_calc() {
  pingHeight = sonar.ping_median(5);             //- Do multiple (5) pings and return median
  pingHeight = sonar.convert_cm(pingHeight);     // then convert to cm
#ifdef MY_DEBUG
  Serial.print("Ping Height raw in cm: ");
  Serial.println(pingHeight);
#endif
  pingHeight  = constrain(pingHeight, sensHeight, (fullHeight - outletHeight) + sensHeight); // keep pingHeight within the expected values
  waterPercent = map(pingHeight, sensHeight, (fullHeight - outletHeight) + sensHeight, 100, 0);   // calculate the percentage of water available
  waterAvail = PI * pow(tankRad, 2) * (((fullHeight - outletHeight) + sensHeight) - pingHeight) / 1000; // calculate water available in litres

  // Write some debug info
#ifdef MY_DEBUG
  Serial.print("Ping Height constrained in cm: ");
  Serial.println(pingHeight);
  Serial.print("Percentage Available: ");
  Serial.println(waterPercent);
  Serial.print("Litres Available: ");
  Serial.println(waterAvail);
#endif
}

I am trying to figure out how the sketch sends the battery info to openhab and how I view it. Any tips or pointers would be most appreciated. Do I have to add another line in the void presentation for the voltage? And should Openhab discover the voltage data as another Thing?

Cheers
Crumpy