weather_station/firmware/weather_station.ino

/*********************************************************************************
 *
 *  weather_station is a weatherstation build around the SparkFun weather meter
 *  It can measure wind speed, wind gust , wind direction, rain fall, temperature,
 *  humidity and air pressure and has an RS-485 ModBus interface for your convenience. 
 *
 * (C)2023 M.T. Konstapel https://meezenest.nl/mees
 *
 * This file is part of weather_station
 *
 *    weather_station is free software: you can redistribute it and/or modify
 *    it under the terms of the GNU General Public License as published by
 *    the Free Software Foundation, either version 3 of the License, or
 *    (at your option) any later version.
 *
 *    weather_station is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with weather_station. If not, see <https://www.gnu.org/licenses/>.
 *
 **********************************************************************************/
#include <ModbusSerial.h>
#include "SparkFun_Weather_Meter_Kit_Arduino_Library.h"

//I2C
#include <Wire.h>
#include "i2c.h"

//Temperature and humidit sensor
#include "i2c_SI7021.h"
SI7021 si7021;

/**************************/
/* Configurable variables */
/**************************/
// Sparkfun weather station
int windDirectionPin = A0;
int windSpeedPin = 2;
int rainfallPin = 3;
// RS485 driver
#define RS485_RE 11            // Tight to RS485_DE and must be configured as an input to prevent a short circuit
#define RS485_DE 12
// Used Pins
const int TxenPin = RS485_DE; // -1 disables the feature, change that if you are using an RS485 driver, this pin would be connected to the DE and /RE pins of the driver.
// ModBus address
const byte SlaveId = 14;
/* Modbus Registers Offsets (0-9999)
 *
 * 30000: Weater station ID (0x5758)
 * 30001: Wind direction (degrees)
 * 30002: Wind speed (average over 10 minutes in km/h)
 * 30003: Wind gust (peak wind speed in the last 10 minutes in km/h)
 * 30004: Temperature (degrees Celcius)
 * 30005: Rain last hour (l/m2)
 * 30006: Rain last 24 hours (l/m2)
 * 30007: Rain since midnight (l/m2)
 * 30008: Humidity (percent)
 * 30009: Barometric pressure (hPa)
 *
 */
const int SensorIDIreg                = 0;
const int SensorWindDirectionIreg     = 1;
const int SensorWindSpeedIreg         = 2;
const int SensorWindGustIreg          = 3;
const int SensorTemperatureIreg       = 4;
const int SensorRainIreg              = 5;
const int SensorRainLast24Ireg        = 6;
const int SensorRainSinceMidnightIreg = 7;
const int SensorHumidityIreg          = 8;
const int SensorPressureIreg          = 9;
// RS-485 serial port 
#define MySerial Serial // define serial port used, Serial most of the time, or Serial1, Serial2 ... if available
const unsigned long Baudrate = 9600;
/******************************/
/* END Configurable variables */
/******************************/

// Create an instance of the weather meter kit
SFEWeatherMeterKit weatherMeterKit(windDirectionPin, windSpeedPin, rainfallPin);

// ModbusSerial object
ModbusSerial mb (MySerial, SlaveId, TxenPin);

unsigned long ts;
unsigned long HourTimer;
int WindGustData1[30];
unsigned char WindGustData1Counter=0;
int WindGustData2[10];
unsigned char WindGustData2Counter=0;
int WindAverageData1[30];
unsigned char WindAverageData1Counter=0;
int WindAverageData2[10];
unsigned char WindAverageData2Counter=0;
int RainPerHour[24];
unsigned char RainPerHourCounter=0;

struct MeasuredData {
  int WindDirection;
  int WindSpeed;
  int WindGust;
  int Rain;
  int RainLast24;
  int SensorRainSinceMidnight;
  int Pressure;

  float Temperature;
  float Humidity;

  bool HeaterStatus = 0;
} MeasuredData;

// Read Si7021 sensor and process data
void ReadSi7021 (void)
{
    si7021.triggerMeasurement();
    si7021.getHumidity(MeasuredData.Humidity);
    si7021.getTemperature(MeasuredData.Temperature);
    // Scale for more decimal positions when converted to integer value for ModBus
    MeasuredData.Humidity *= 100;
    MeasuredData.Temperature *= 100;

    //If humidity is larger than 80% switch on heater to get more acurate measurement
    //Switch off when lower than 78% (hysteresis)
    if (MeasuredData.Humidity > 80 && !MeasuredData.HeaterStatus) {
      Serial.print(F("Heater on."));
      MeasuredData.HeaterStatus = 1;
      si7021.setHeater(MeasuredData.HeaterStatus);
    }
    if (MeasuredData.Humidity < 78 && MeasuredData.HeaterStatus) {
      Serial.print(F("Heater off."));
      MeasuredData.HeaterStatus = 0;
      si7021.setHeater(MeasuredData.HeaterStatus);
    }

}

int MaxOfArray (int array[], unsigned int length)
{
  int maximum_value = 0;
  
  while (length--)
  {
    if (array[length] > maximum_value)
      maximum_value = array[length];
  }
  return maximum_value;
}

int AverageOfArray (int array[], unsigned int length)
{
  int tmp_value = 0;
  unsigned char tmp_length = length;
  int average_value = 0;
 
  while (length--)
  {
    tmp_value += array[length];
  }
  average_value = tmp_value/tmp_length;

  return average_value;
}

// Call this function every 2 seconds
void ReadSparkfunWeatherStation (void)
{
  unsigned char cnt=0;

  float tmpRegister;

  MeasuredData.WindDirection = weatherMeterKit.getWindDirection();
  tmpRegister = 100*(weatherMeterKit.getWindSpeed())/3.6;  // Use float for conversion to m/s times 100, than put it in integer register for ModBus
  MeasuredData.WindSpeed = tmpRegister;
  tmpRegister = 100*weatherMeterKit.getTotalRainfall();    // Use float for conversion to l/m2 times 100, than put it in integer register for ModBus
  MeasuredData.Rain = tmpRegister;

  // FIFO for calculating wind gust of last 10 minutes
  // to preserve valuable RAM we caanot store all measurements of the last 10 minutes.
  // So we use a hack: store the last 30 values in a FIFO and every minute we store the maximum value from this FIFO in another FIFO.
  // This second FIFO is 10 deep: it stores the maximum values of the last 10 minutes.
  // The maximum value from this FIFO is the maximum wind gust of the last 10 minutes.
  if ( WindGustData1Counter < 29 )
  {
    WindGustData1Counter++;
  }
  else
  {
    if ( WindGustData2Counter < 9 )
    {
      WindGustData2Counter++;
    }
    else
    {
      WindGustData2Counter=0;
    }
    WindGustData2[WindGustData2Counter] = MaxOfArray(WindGustData1, 30);
    WindGustData1Counter=0;
  }
  WindGustData1[WindGustData1Counter] = MeasuredData.WindSpeed;
  MeasuredData.WindGust= MaxOfArray(WindGustData2, 10);

  // Smart FIFO, same as for Wind Gust, but now for average wind speed over 10 minutes
  if ( WindAverageData1Counter < 29 )
  {
    WindAverageData1Counter++;
  }
  else
  {
    if ( WindAverageData2Counter < 9 )
    {
       WindAverageData2Counter++;
    }
    else
    {
      WindAverageData2Counter=0;
    }
    WindAverageData2[WindAverageData2Counter] = AverageOfArray(WindAverageData1, 30);
    WindAverageData1Counter=0;
    WindAverageData1[WindAverageData1Counter] = MeasuredData.WindSpeed;
  }
  WindAverageData1[WindAverageData1Counter] = MeasuredData.WindSpeed;
  MeasuredData.WindSpeed = AverageOfArray(WindAverageData2, 10);

  // Record rainfall in one hour, save last 24 readings in FIFO
  if ( ( millis() - HourTimer) >= 3.6e+6) {
    
    HourTimer = millis();

    if ( RainPerHourCounter < 23 )
    {
      RainPerHourCounter++;
    } else {
      RainPerHourCounter=0;
    }
    RainPerHour[RainPerHourCounter] = MeasuredData.Rain;
    weatherMeterKit.resetTotalRainfall();

    // Calculate rain fall in the last 24 hours
    MeasuredData.RainLast24=0;
    for (cnt=0; cnt<24;cnt++) {
      MeasuredData.RainLast24 += RainPerHour[cnt];
    }

  }
  MeasuredData.Rain = RainPerHour[RainPerHourCounter];
}

void setup() {

  MySerial.begin (Baudrate); // works on all boards but the configuration is 8N1 which is incompatible with the MODBUS standard
  // prefer the line below instead if possible
  // MySerial.begin (Baudrate, MB_PARITY_EVEN);

  //Setup control lines for RS485 driver
  pinMode(RS485_RE,INPUT);        // In hardware connected to RS485_DE. Should be input to prevent a short circuit!
  pinMode(RS485_DE,OUTPUT);
  digitalWrite(RS485_DE,LOW);

  mb.config (Baudrate);
  mb.setAdditionalServerData ("TEMP_SENSOR"); // for Report Server ID function (0x11)

  // Add SensorIreg registers - Use addIreg() for analog Inputs
  mb.addIreg (SensorIDIreg);
  mb.addIreg (SensorWindDirectionIreg);
  mb.addIreg (SensorWindSpeedIreg);
  mb.addIreg (SensorWindGustIreg);
  mb.addIreg (SensorTemperatureIreg);
  mb.addIreg (SensorRainIreg);
  mb.addIreg (SensorRainLast24Ireg);
  mb.addIreg (SensorRainSinceMidnightIreg);
  mb.addIreg (SensorHumidityIreg);
  mb.addIreg (SensorPressureIreg);
    
  // Set Weather station ID
  mb.Ireg (SensorIDIreg, 0x5758);

  Serial.println(F("Weather station"));

  //Initialize Si7021 sensor
  Serial.print(F("Humidity sensor SI7021 "));
  if (si7021.initialize())
    Serial.println(F("found"));
  else
  {
    Serial.println(F("missing"));
    while(1) {};
  }

    // Expected ADC values have been defined for various platforms in the
    // library, however your platform may not be included. This code will check
    // if that's the case
#ifdef SFE_WMK_PLAFTORM_UNKNOWN
    // The platform you're using hasn't been added to the library, so the
    // expected ADC values have been calculated assuming a 10k pullup resistor
    // and a perfectly linear 16-bit ADC. Your ADC likely has a different
    // resolution, so you'll need to specify it here:
    weatherMeterKit.setADCResolutionBits(10);
#endif
    // Begin weather meter kit
    weatherMeterKit.begin();

   ts = millis();
   RainPerHourCounter = ts;
}

void loop() {

  // Call once inside loop() - all magic here
  mb.task();
  
  // Read each two seconds
  if ( ( millis() - ts) >= 2000) {
    
    ts = millis();

    // Read temperature and humidity
    ReadSi7021();

    // Read Wind and rain
    ReadSparkfunWeatherStation();

    // Setting Sparkfun weather station registers
    mb.Ireg (SensorWindDirectionIreg, MeasuredData.WindDirection);
    mb.Ireg (SensorWindSpeedIreg, MeasuredData.WindSpeed);
    mb.Ireg (SensorWindGustIreg, MeasuredData.WindGust);
    mb.Ireg (SensorRainIreg, MeasuredData.Rain);
    mb.Ireg (SensorRainLast24Ireg, MeasuredData.RainLast24);
    mb.Ireg (SensorTemperatureIreg, MeasuredData.Temperature);
    mb.Ireg (SensorHumidityIreg, MeasuredData.Humidity);

    }
}