Slim Node Si7021 sensor example

LastSamurai

@GertSanders Thanks, I don't know why I didn't realize that ;)
I will try that out tomorrow.

rsachoc

@LastSamurai I'm having a go as well at updating the .ino file with the different library, but I'm not a coder so I'm "having a hack" - if you have any luck could you post your code?

LastSamurai

@rsachoc Yes, I actually just tried it out and its working.
Here is my code for now (just for testing):
I basically just switched libraries

/* Sketch with Si7021 and battery monitoring.
by m26872, 20151109 
Changed by LastSamurai
15052016
*/
#include <MySensor.h>  
#include <Wire.h>
#include <SPI.h>
#include <SparkFunHTU21D.h>
#include <RunningAverage.h>

//#define DEBUG

#ifdef DEBUG
#define DEBUG_SERIAL(x) Serial.begin(x)
#define DEBUG_PRINT(x) Serial.print(x)
#define DEBUG_PRINTLN(x) Serial.println(x)
#else
#define DEBUG_SERIAL(x)
#define DEBUG_PRINT(x) 
#define DEBUG_PRINTLN(x) 
#endif

#define NODE_ID 100             // <<<<<<<<<<<<<<<<<<<<<<<<<<<   Enter Node_ID
#define CHILD_ID_TEMP 0
#define CHILD_ID_HUM 1
// #define SLEEP_TIME 15000 // 15s for DEBUG
#define SLEEP_TIME 300000   // 5 min
#define FORCE_TRANSMIT_CYCLE 36  // 5min*12=1/hour, 5min*36=1/3hour 
#define BATTERY_REPORT_CYCLE 2016   // Once per 5min   =>   12*24*7 = 2016 (one report/week)
#define VMIN 1900
#define VMAX 3300
#define HUMI_TRANSMIT_THRESHOLD 3.0  // THRESHOLD tells how much the value should have changed since last time it was transmitted.
#define TEMP_TRANSMIT_THRESHOLD 0.5
#define AVERAGES 2

int batteryReportCounter = BATTERY_REPORT_CYCLE - 1;  // to make it report the first time.
int measureCount = 0;
float lastTemperature = -100;
int lastHumidity = -100;

RunningAverage raHum(AVERAGES);
HTU21D humiditySensor;

MySensor gw;
MyMessage msgTemp(CHILD_ID_TEMP,V_TEMP); // Initialize temperature message
MyMessage msgHum(CHILD_ID_HUM,V_HUM);

void setup() {
  DEBUG_SERIAL(9600);    // <<<<<<<<<<<<<<<<<<<<<<<<<< Note BAUD_RATE in MySensors.h
  DEBUG_PRINTLN("Serial started");
  
  DEBUG_PRINT("Voltage: ");
  DEBUG_PRINT(readVcc()); 
  DEBUG_PRINTLN(" mV");

  delay(500);
  DEBUG_PRINT("Internal temp: ");
  DEBUG_PRINT(GetInternalTemp()); // Probably not calibrated. Just to print something.
  DEBUG_PRINTLN(" *C");

  delay(500); // Allow time for radio if power useed as reset
  gw.begin(NULL, NODE_ID);
  gw.sendSketchInfo("TempHumTest2", "1.0 17052016"); 
  gw.present(CHILD_ID_TEMP, S_TEMP);   // Present sensor to controller
  gw.present(CHILD_ID_HUM, S_HUM);
  DEBUG_PRINT("Node and "); DEBUG_PRINTLN("2 children presented.");
  
  raHum.clear();
  humiditySensor.begin();  
}

void loop() { 

  measureCount ++;
  batteryReportCounter ++;
  bool forceTransmit = false;
  
  if (measureCount > FORCE_TRANSMIT_CYCLE) {
    forceTransmit = true; 
  }
  sendTempHumidityMeasurements(forceTransmit);
/*
  // Read and print internal temp
  float temperature0 = static_cast<float>(static_cast<int>((GetInternalTemp()+0.5) * 10.)) / 10.;
  DEBUG_PRINT("Internal Temp: "); DEBUG_PRINT(temperature0); DEBUG_PRINTLN(" *C");        
*/
  // Check battery
  if (batteryReportCounter >= BATTERY_REPORT_CYCLE) {
    long batteryVolt = readVcc();
    DEBUG_PRINT("Battery voltage: "); DEBUG_PRINT(batteryVolt); DEBUG_PRINTLN(" mV");
    uint8_t batteryPcnt = constrain(map(batteryVolt,VMIN,VMAX,0,100),0,255);   
    DEBUG_PRINT("Battery percent: "); DEBUG_PRINT(batteryPcnt); DEBUG_PRINTLN(" %");
    gw.sendBatteryLevel(batteryPcnt);
    batteryReportCounter = 0;
  }
  
  gw.sleep(SLEEP_TIME);
}

// function for reading Vcc by reading 1.1V reference against AVcc. Based from http://provideyourown.com/2012/secret-arduino-voltmeter-measure-battery-voltage/
// To calibrate reading replace 1125300L with scale_constant = internal1.1Ref * 1023 * 1000, where internal1.1Ref = 1.1 * Vcc1 (per voltmeter) / Vcc2 (per readVcc() function) 
long readVcc() {
  // set the reference to Vcc and the measurement to the internal 1.1V reference
  ADMUX = _BV(REFS0) | _BV(MUX3) | _BV(MUX2) | _BV(MUX1);
  delay(2); // Wait for Vref to settle
  ADCSRA |= _BV(ADSC); // Start conversion
  while (bit_is_set(ADCSRA,ADSC)); // measuring
  uint8_t low  = ADCL; // must read ADCL first - it then locks ADCH  
  uint8_t high = ADCH; // unlocks both
  long result = (high<<8) | low;
  result = 1125300L / result; // Calculate Vcc (in mV); 1125300 = 1.1*1023*1000
  return result; // Vcc in millivolts
}
// function for reading internal temp. From http://playground.arduino.cc/Main/InternalTemperatureSensor 
double GetInternalTemp(void) {  // (Both double and float are 4 byte in most arduino implementation)
  unsigned int wADC;
  double t;
  // The internal temperature has to be used with the internal reference of 1.1V. Channel 8 can not be selected with the analogRead function yet.
  ADMUX = (_BV(REFS1) | _BV(REFS0) | _BV(MUX3));   // Set the internal reference and mux.
  ADCSRA |= _BV(ADEN);  // enable the ADC
  delay(20);            // wait for voltages to become stable.
  ADCSRA |= _BV(ADSC);  // Start the ADC
  while (bit_is_set(ADCSRA,ADSC));   // Detect end-of-conversion
  wADC = ADCW;   // Reading register "ADCW" takes care of how to read ADCL and ADCH.
  t = (wADC - 88.0 ) / 1.0;   // The default offset is 324.31.
  return (t);   // The returned temperature in degrees Celcius.
}

/*********************************************
 * * Sends temperature and humidity from Si7021 sensor
 * Parameters
 * - force : Forces transmission of a value (even if it's the same as previous measurement)
 *********************************************/
void sendTempHumidityMeasurements(bool force) {
  bool tx = force;
  
  float temperature = humiditySensor.readTemperature();
  DEBUG_PRINT("T: ");DEBUG_PRINTLN(temperature);

  float diffTemp = abs(lastTemperature - temperature);
  DEBUG_PRINT(F("TempDiff :"));DEBUG_PRINTLN(diffTemp);

  if (diffTemp > TEMP_TRANSMIT_THRESHOLD || tx) {
    gw.send(msgTemp.set(temperature,1));
    lastTemperature = temperature;
    measureCount = 0;
    DEBUG_PRINTLN("T sent!");
  }
  
  int humidity = humiditySensor.readHumidity();
  DEBUG_PRINT("H: ");DEBUG_PRINTLN(humidity);

  raHum.addValue(humidity);
  humidity = raHum.getAverage();  // MA sample imply reasonable fast sample frequency
  float diffHum = abs(lastHumidity - humidity);
  DEBUG_PRINT(F("HumDiff  :"));DEBUG_PRINTLN(diffHum); 

  if (diffHum > HUMI_TRANSMIT_THRESHOLD || tx) {
    gw.send(msgHum.set(humidity));
    lastHumidity = humidity;
    measureCount = 0;
    DEBUG_PRINTLN("H sent!");
  }

}

rsachoc

@LastSamurai thanks, progress, I'm getting this now, which means it's working! Finally, a working node from a complete rookie like me!

Serial started
Voltage: 3389 mV
Internal temp: 266.00 *C
send: 100-100-0-0 s=255,c=3,t=15,pt=2,l=2,sg=0,st=ok:0
send: 100-100-0-0 s=255,c=0,t=17,pt=0,l=5,sg=0,st=ok:1.5.4
send: 100-100-0-0 s=255,c=3,t=6,pt=1,l=1,sg=0,st=ok:0
read: 0-0-100 s=255,c=3,t=15,pt=0,l=2,sg=0:
sensor started, id=100, parent=0, distance=1
send: 100-100-0-0 s=255,c=3,t=11,pt=0,l=12,sg=0,st=fail:TempHumTest2
send: 100-100-0-0 s=255,c=3,t=12,pt=0,l=12,sg=0,st=fail:1.0 17052016
send: 100-100-0-0 s=0,c=0,t=6,pt=0,l=0,sg=0,st=fail:
send: 100-100-0-0 s=1,c=0,t=7,pt=0,l=0,sg=0,st=fail:
Node and 2 children presented.
T: 998.00
TempDiff :1098.00
send: 100-100-0-0 s=0,c=1,t=0,pt=7,l=5,sg=0,st=fail:998.0
T sent!
H: 118
HumDiff  :218.00
send: 100-100-0-0 s=1,c=1,t=1,pt=2,l=2,sg=0,st=ok:118
H sent!
Battery voltage: 3359 mV
Battery percent: 104 %
send: 100-100-0-0 s=255,c=3,t=0,pt=1,l=1,sg=0,st=ok:104

I think that the readings are not accurate though, not sure why, but I'll have a go at figuring our why anyway!

GertSanders

@rsachoc
Congrats !!!

m26872

@GertSanders Thx a lot for your help! I had no clue about the HTU21D lib.

badmannen

This post is deleted!

siod

so with the correct library there is no need to solder those 3 spots together!?

GertSanders

@siod
The "spots" are there to connect the pullup resistors to the SDA and SCL lines. This is always needed, regardless of the library of the board onto which you connect the sensor board does not provide pullup resistors itself. On a minimal board like the one in this thread, this is not the case, so the pull up resistors are needed.

siod

ok, thanks for making it clear for me Gert!!

update:

finally found time to build my sensor and it seems to work fine, will do more testing but for now my results are:

7.5 uA when sleeping, 15,3 mA when working (every 15 minutes for about 2seconds, but I think my cheap multimeter gives bad readings on those spikes, I guess it´s only around 1 mA)

seems to be okay, isn´t it?

edit:

I have 2 reed switches attached. I recognized that I have +0,10 mA for each reed switch when activated. So when reed switches are both touching their counterpart I have a sleeping consumption of 0,20 mA. Why is that??

jacikaas

Hello,

I'm trying to convert existing Si7021 sensor code from 1.5 to 2.0.0 library. I change the code and then I was getting an error which said:

Si7021_sensor_MySensors_2.0.0:158: error: 'si7021_env' has no member named 'humidityPercent'
   int humidity = data.humidityPercent;
                       ^
exit status 1
'si7021_env' has no member named 'humidityPercent'

Then I chech the Si7021 library, and how I saw there wasn't member 'humidityPercent', but there was a member 'humidityBasisPoints'.

So I change line from:

  int humidity = data.humidityPercent;

...to:

  int humidity = data.humidityBasisPoints;

Then code compiles and I upload it to Slim Node Si7021. I leave sensor and today I checked it log on Domoticz. I have this:

Temperature looks ok, but Humidity value jumping a lot, thats why I don't want to believe it is true.

Could someone, who has a 2.0.0 library and Si7021 sensor chech is it same situation? Becose I have only one Si7021 sensor.
Maybe someone could look also on the code and say if I convert it right?

Converted code:

/* Sketch with Si7021 and battery monitoring.
by m26872, 20151109 
*/

#define MY_DEBUG
#define MY_RADIO_NRF24
#define MY_NODE_ID 5             // <<<<<<<<<<<<<<<<<<<<<<<<<<<   Enter Node_ID
#define MY_BAUD_RATE 115200

#include <MySensors.h>  
#include <Wire.h>
#include <SI7021.h>
#include <SPI.h>
#include <RunningAverage.h>

//#define DEBUG

#ifdef DEBUG
#define DEBUG_SERIAL(x) Serial.begin(x)
#define DEBUG_PRINT(x) Serial.print(x)
#define DEBUG_PRINTLN(x) Serial.println(x)
#else
#define DEBUG_SERIAL(x)
#define DEBUG_PRINT(x) 
#define DEBUG_PRINTLN(x) 
#endif

#define CHILD_ID_TEMP 0
#define CHILD_ID_HUM 1
// #define SLEEP_TIME 15000 // 15s for DEBUG
#define SLEEP_TIME 300000   // 5 min
#define FORCE_TRANSMIT_CYCLE 36  // 5min*12=1/hour, 5min*36=1/3hour 
#define BATTERY_REPORT_CYCLE 2880   // Once per 5min   =>   12*24*7 = 2016 (one report/week)
#define VMIN 1900
#define VMAX 3300
#define HUMI_TRANSMIT_THRESHOLD 3.0  // THRESHOLD tells how much the value should have changed since last time it was transmitted.
#define TEMP_TRANSMIT_THRESHOLD 0.5
#define AVERAGES 2

int batteryReportCounter = BATTERY_REPORT_CYCLE - 1;  // to make it report the first time.
int measureCount = 0;
float lastTemperature = -100;
int lastHumidity = -100;

RunningAverage raHum(AVERAGES);
SI7021 humiditySensor;

MyMessage msgTemp(CHILD_ID_TEMP,V_TEMP); // Initialize temperature message
MyMessage msgHum(CHILD_ID_HUM,V_HUM);


void presentation()  
{ 
  sendSketchInfo("EgTmpHumBat5min", "1.0 151106");
  present(CHILD_ID_TEMP, S_TEMP);   // Present sensor to controller
  present(CHILD_ID_HUM, S_HUM);
}


void setup() {
  DEBUG_SERIAL(115200);    // <<<<<<<<<<<<<<<<<<<<<<<<<< Note BAUD_RATE in MySensors.h
  DEBUG_PRINTLN("Serial started");
  
  DEBUG_PRINT("Voltage: ");
  DEBUG_PRINT(readVcc()); 
  DEBUG_PRINTLN(" mV");
/*
  delay(500);
  DEBUG_PRINT("Internal temp: ");
  DEBUG_PRINT(GetInternalTemp()); // Probably not calibrated. Just to print something.
  DEBUG_PRINTLN(" *C");
*/  
  delay(500); // Allow time for radio if power useed as reset
  DEBUG_PRINT("Node and "); DEBUG_PRINTLN("2 children presented.");
  
  raHum.clear();
  
}

void loop() { 

  measureCount ++;
  batteryReportCounter ++;
  bool forceTransmit = false;
  
  if (measureCount > FORCE_TRANSMIT_CYCLE) {
    forceTransmit = true; 
  }
  sendTempHumidityMeasurements(forceTransmit);
/*
  // Read and print internal temp
  float temperature0 = static_cast<float>(static_cast<int>((GetInternalTemp()+0.5) * 10.)) / 10.;
  DEBUG_PRINT("Internal Temp: "); DEBUG_PRINT(temperature0); DEBUG_PRINTLN(" *C");        
*/
  // Check battery
  if (batteryReportCounter >= BATTERY_REPORT_CYCLE) {
    long batteryVolt = readVcc();
    DEBUG_PRINT("Battery voltage: "); DEBUG_PRINT(batteryVolt); DEBUG_PRINTLN(" mV");
    uint8_t batteryPcnt = constrain(map(batteryVolt,VMIN,VMAX,0,100),0,255);   
    DEBUG_PRINT("Battery percent: "); DEBUG_PRINT(batteryPcnt); DEBUG_PRINTLN(" %");
    sendBatteryLevel(batteryPcnt);
    batteryReportCounter = 0;
  }
  
  sleep(SLEEP_TIME);
}

// function for reading Vcc by reading 1.1V reference against AVcc. Based from http://provideyourown.com/2012/secret-arduino-voltmeter-measure-battery-voltage/
// To calibrate reading replace 1125300L with scale_constant = internal1.1Ref * 1023 * 1000, where internal1.1Ref = 1.1 * Vcc1 (per voltmeter) / Vcc2 (per readVcc() function) 
long readVcc() {
  // set the reference to Vcc and the measurement to the internal 1.1V reference
  ADMUX = _BV(REFS0) | _BV(MUX3) | _BV(MUX2) | _BV(MUX1);
  delay(2); // Wait for Vref to settle
  ADCSRA |= _BV(ADSC); // Start conversion
  while (bit_is_set(ADCSRA,ADSC)); // measuring
  uint8_t low  = ADCL; // must read ADCL first - it then locks ADCH  
  uint8_t high = ADCH; // unlocks both
  long result = (high<<8) | low;
  result = 1125300L / result; // Calculate Vcc (in mV); 1125300 = 1.1*1023*1000
  return result; // Vcc in millivolts
}
// function for reading internal temp. From http://playground.arduino.cc/Main/InternalTemperatureSensor 
double GetInternalTemp(void) {  // (Both double and float are 4 byte in most arduino implementation)
  unsigned int wADC;
  double t;
  // The internal temperature has to be used with the internal reference of 1.1V. Channel 8 can not be selected with the analogRead function yet.
  ADMUX = (_BV(REFS1) | _BV(REFS0) | _BV(MUX3));   // Set the internal reference and mux.
  ADCSRA |= _BV(ADEN);  // enable the ADC
  delay(20);            // wait for voltages to become stable.
  ADCSRA |= _BV(ADSC);  // Start the ADC
  while (bit_is_set(ADCSRA,ADSC));   // Detect end-of-conversion
  wADC = ADCW;   // Reading register "ADCW" takes care of how to read ADCL and ADCH.
  t = (wADC - 88.0 ) / 1.0;   // The default offset is 324.31.
  return (t);   // The returned temperature in degrees Celcius.
}

/*********************************************
 * * Sends temperature and humidity from Si7021 sensor
 * Parameters
 * - force : Forces transmission of a value (even if it's the same as previous measurement)
 *********************************************/
void sendTempHumidityMeasurements(bool force) {
  bool tx = force;

  si7021_env data = humiditySensor.getHumidityAndTemperature();
  
  float temperature = data.celsiusHundredths / 100.0;
  DEBUG_PRINT("T: ");DEBUG_PRINTLN(temperature);
  float diffTemp = abs(lastTemperature - temperature);
  DEBUG_PRINT(F("TempDiff :"));DEBUG_PRINTLN(diffTemp);
  if (diffTemp > TEMP_TRANSMIT_THRESHOLD || tx) {
    send(msgTemp.set(temperature,1));
    lastTemperature = temperature;
    measureCount = 0;
    DEBUG_PRINTLN("T sent!");
  }
  
  int humidity = data.humidityPercent;
  DEBUG_PRINT("H: ");DEBUG_PRINTLN(humidity);
  raHum.addValue(humidity);
  humidity = raHum.getAverage();  // MA sample imply reasonable fast sample frequency
  float diffHum = abs(lastHumidity - humidity);  
  DEBUG_PRINT(F("HumDiff  :"));DEBUG_PRINTLN(diffHum); 
  if (diffHum > HUMI_TRANSMIT_THRESHOLD || tx) {
    send(msgHum.set(humidity));
    lastHumidity = humidity;
    measureCount = 0;
    DEBUG_PRINTLN("H sent!");
  }

}

Thank You!

AWI

@jacikaas where did you get the si7021 library? Take a look at the sensebender sketch for a good reference.

jacikaas

@AWI
I download Si7021 library from here: https://github.com/LowPowerLab/SI7021

I was heard about Sensbender node, but never look deeper what is in it. I will look at it and try to understand whats in there. I just learning about all that stuff, so it will be good practice :blush:

AWI

@jacikaas that's the way to go. The sensebender sketch contains some rather nice best practices for low power. You best replace the si library with the one in the MySensors examples on github.

jacikaas

@AWI I try to replace library from this one https://github.com/LowPowerLab/SI7021 to this one https://github.com/mysensors/MySensorsArduinoExamples

to work it I need to return variable name from:

  int humidity = data.humidityBasisPoints;

to:

  int humidity = data.humidityPercent;

I think this library https://github.com/LowPowerLab/SI7021 was updated, so it is not suitable for this one code. Now I test it again and everything looks fine:
0_1471719934242_chart (1).jpeg

Temperature and humidity node unregister or stop working repeatedly for about 2 hours (2h25min, 2.20, 1.50...). But after that it start to send data again, for some time and then goes around again. :) I will try to understand why it happening too.

wergeld

I am trying to build the code using the HTU21D sensors. This built fine under 1.4 and 1.5 but now under v2 of MySensors I am getting this error:

C:\Users\wergeld\Documents\Arduino\SlimNodeSi7021\SlimNodeSi7021.ino:4:24: fatal error: MySensor.h: No such file or directory

 #include <MySensor.h>  

                        ^

compilation terminated.

exit status 1
Error compiling for board APM Optiboot internal 1MHz noBOD 9600baud.

Okay, so I change my reference to:

#include <MySensors.h>

And I get this lovely error:

In file included from C:\Users\wergeld\Documents\Arduino\SlimNodeSi7021\SlimNodeSi7021.ino:4:0:

C:\Users\wergeld\Documents\Arduino\libraries\MySensors-master/MySensors.h:287:4: error: #error No forward link or gateway feature activated. This means nowhere to send messages! Pretty pointless.

   #error No forward link or gateway feature activated. This means nowhere to send messages! Pretty pointless.

    ^

exit status 1
Error compiling for board APM Optiboot internal 1MHz noBOD 9600baud.

So, other than slamming my head against my desk how can I solve this?

wergeld

Well, I solved it by modifying the code to 2.0 spec. Good lord I need sleep. :anguished:
Working on debugging temp outputs now to Ethernet Gateway running on my Uno. Or I will sleep...

wergeld

Okay, I now have a soldered node and serial gateway setup to my laptop for testing. It presents the sensor node! The name and available sensors is correct. Howevr, it never sends any message payload with temp/hum or battery values. I am using the HTU21D without soldering those 3 pads on it together. I need to get myself a 3.3v FTDI cable so I can serially debug I guess. But, still! Progress.

wergeld

After soldering the 3 pads on the HTU21D I am now reading data and it is being sent to my test serial gateway. Need to measure current usage but at least it is functional.

wergeld

Okay, seeing something odd. The force transmit does not appear to be working.
Here is my current sketch:

#define MY_RADIO_NRF24

#include <MyConfig.h>
#include <MySensors.h>

/* Sketch with Si7021 and battery monitoring.
by m26872, 20151109 
*/
//#include <MySensors.h>  
#include <Wire.h>
#include <SparkFunHTU21D.h>
#include <SPI.h>
#include <RunningAverage.h>

//#define DEBUG

#ifdef DEBUG
#define DEBUG_SERIAL(x) Serial.begin(x)
#define DEBUG_PRINT(x) Serial.print(x)
#define DEBUG_PRINTLN(x) Serial.println(x)
#else
#define DEBUG_SERIAL(x)
#define DEBUG_PRINT(x) 
#define DEBUG_PRINTLN(x) 
#endif

#define NODE_ID 132             // <<<<<<<<<<<<<<<<<<<<<<<<<<<   Enter Node_ID
#define CHILD_ID_TEMP 0
#define CHILD_ID_HUM 1
// #define SLEEP_TIME 15000 // 15s for DEBUG
#define SLEEP_TIME 300000   // 5 min
#define FORCE_TRANSMIT_CYCLE 36  // 5min*12=1/hour, 5min*36=1/3hour 
#define BATTERY_REPORT_CYCLE 2880   // Once per 5min   =>   12*24*7 = 2016 (one report/week)
#define VMIN 1900
#define VMAX 3300
#define HUMI_TRANSMIT_THRESHOLD 3.0  // THRESHOLD tells how much the value should have changed since last time it was transmitted.
#define TEMP_TRANSMIT_THRESHOLD 0.5
#define AVERAGES 2

int batteryReportCounter = BATTERY_REPORT_CYCLE - 1;  // to make it report the first time.
int measureCount = 0;
float lastTemperature = -100;
int lastHumidity = -100;

RunningAverage raHum(AVERAGES);
HTU21D humiditySensor;

//MySensor gw;
MyMessage msgTemp(CHILD_ID_TEMP,V_TEMP); // Initialize temperature message
MyMessage msgHum(CHILD_ID_HUM,V_HUM);

void presentation()  
{ 
  sendSketchInfo("HTU21D", "1.0"); 
  present(CHILD_ID_TEMP, S_TEMP);   // Present sensor to controller
  present(CHILD_ID_HUM, S_HUM);
}

void setup() {
  DEBUG_SERIAL(9600);    // <<<<<<<<<<<<<<<<<<<<<<<<<< Note BAUD_RATE in MySensors.h
  DEBUG_PRINTLN("Serial started");
  
  DEBUG_PRINT("Voltage: ");
  DEBUG_PRINT(readVcc()); 
  DEBUG_PRINTLN(" mV");
/*
  delay(500);
  DEBUG_PRINT("Internal temp: ");
  DEBUG_PRINT(GetInternalTemp()); // Probably not calibrated. Just to print something.
  DEBUG_PRINTLN(" *C");
*/  
  delay(500); // Allow time for radio if power useed as reset
  //gw.begin(NULL,NODE_ID);
  //sendSketchInfo("HTU21D", "1.0"); 
  //present(CHILD_ID_TEMP, S_TEMP);   // Present sensor to controller
  //present(CHILD_ID_HUM, S_HUM);
  DEBUG_PRINT("Node and "); DEBUG_PRINTLN("2 children presented.");
  
  raHum.clear();
  
}

void loop() { 

  measureCount ++;
  batteryReportCounter ++;
  bool forceTransmit = false;
  
  if (measureCount > FORCE_TRANSMIT_CYCLE) {
    forceTransmit = true; 
  }
  sendTempHumidityMeasurements(forceTransmit);
/*
  // Read and print internal temp
  float temperature0 = static_cast<float>(static_cast<int>((GetInternalTemp()+0.5) * 10.)) / 10.;
  DEBUG_PRINT("Internal Temp: "); DEBUG_PRINT(temperature0); DEBUG_PRINTLN(" *C");        
*/
  // Check battery
  if (batteryReportCounter >= BATTERY_REPORT_CYCLE) {
    long batteryVolt = readVcc();
    DEBUG_PRINT("Battery voltage: "); DEBUG_PRINT(batteryVolt); DEBUG_PRINTLN(" mV");
    uint8_t batteryPcnt = constrain(map(batteryVolt,VMIN,VMAX,0,100),0,255);   
    DEBUG_PRINT("Battery percent: "); DEBUG_PRINT(batteryPcnt); DEBUG_PRINTLN(" %");
    sendBatteryLevel(batteryPcnt);
    batteryReportCounter = 0;
  }
  
  sleep(SLEEP_TIME);
}

// function for reading Vcc by reading 1.1V reference against AVcc. Based from http://provideyourown.com/2012/secret-arduino-voltmeter-measure-battery-voltage/
// To calibrate reading replace 1125300L with scale_constant = internal1.1Ref * 1023 * 1000, where internal1.1Ref = 1.1 * Vcc1 (per voltmeter) / Vcc2 (per readVcc() function) 
long readVcc() {
  // set the reference to Vcc and the measurement to the internal 1.1V reference
  ADMUX = _BV(REFS0) | _BV(MUX3) | _BV(MUX2) | _BV(MUX1);
  delay(2); // Wait for Vref to settle
  ADCSRA |= _BV(ADSC); // Start conversion
  while (bit_is_set(ADCSRA,ADSC)); // measuring
  uint8_t low  = ADCL; // must read ADCL first - it then locks ADCH  
  uint8_t high = ADCH; // unlocks both
  long result = (high<<8) | low;
  result = 1125300L / result; // Calculate Vcc (in mV); 1125300 = 1.1*1023*1000
  return result; // Vcc in millivolts
}
// function for reading internal temp. From http://playground.arduino.cc/Main/InternalTemperatureSensor 
double GetInternalTemp(void) {  // (Both double and float are 4 byte in most arduino implementation)
  unsigned int wADC;
  double t;
  // The internal temperature has to be used with the internal reference of 1.1V. Channel 8 can not be selected with the analogRead function yet.
  ADMUX = (_BV(REFS1) | _BV(REFS0) | _BV(MUX3));   // Set the internal reference and mux.
  ADCSRA |= _BV(ADEN);  // enable the ADC
  delay(20);            // wait for voltages to become stable.
  ADCSRA |= _BV(ADSC);  // Start the ADC
  while (bit_is_set(ADCSRA,ADSC));   // Detect end-of-conversion
  wADC = ADCW;   // Reading register "ADCW" takes care of how to read ADCL and ADCH.
  t = (wADC - 88.0 ) / 1.0;   // The default offset is 324.31.
  return (t);   // The returned temperature in degrees Celcius.
}

/*********************************************
 * * Sends temperature and humidity from Si7021 sensor
 * Parameters
 * - force : Forces transmission of a value (even if it's the same as previous measurement)
 *********************************************/
void sendTempHumidityMeasurements(bool force) {
  bool tx = force;
  
  float temperature = humiditySensor.readTemperature();
  DEBUG_PRINT("T: ");DEBUG_PRINTLN(temperature);

  float diffTemp = abs(lastTemperature - temperature);
  DEBUG_PRINT(F("TempDiff :"));DEBUG_PRINTLN(diffTemp);

  if (diffTemp > TEMP_TRANSMIT_THRESHOLD || tx) {
    send(msgTemp.set(temperature,1));
    lastTemperature = temperature;
    measureCount = 0;
    DEBUG_PRINTLN("T sent!");
  }
  
  int humidity = humiditySensor.readHumidity();
  DEBUG_PRINT("H: ");DEBUG_PRINTLN(humidity);

  raHum.addValue(humidity);
  humidity = raHum.getAverage();  // MA sample imply reasonable fast sample frequency
  float diffHum = abs(lastHumidity - humidity);
  DEBUG_PRINT(F("HumDiff  :"));DEBUG_PRINTLN(diffHum); 

  if (diffHum > HUMI_TRANSMIT_THRESHOLD || tx) {
    send(msgHum.set(humidity));
    lastHumidity = humidity;
    measureCount = 0;
    DEBUG_PRINTLN("H sent!");
  }
}

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Slim Node Si7021 sensor example

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