MQTT Sensor Station

/* {{{ Node - Sensor Station - Garden

 Node - Sensor Station - Garden
 ------------------------------

 Sensor Station Node (v1) located in the garden does the following:

 1) Temperature - read temperature from DHT22 sensor
 2) Humudity - read humidity from DHT22 sensor
 3) Dew point - calculate dew point from temperature and humudity values obtained from DHT22 sensor
 4) Light - light intensity (0-1024) from Keyes photo sensor
 5) Pressure - barometric pressure from BMP180 sensor

 MQTT channels:

 /h/h/temperature
 /h/h/pressure
 /h/h/humudity
 /h/h/dewpoint
 /h/h/light
 /h/s

}}} */
// {{{ include
#include <SPI.h>
#include <Ethernet.h>
#include <PubSubClient.h>
#include <Wire.h>
#include <OneWire.h>
#include <DallasTemperature.h>
#include <dht.h>
#include <SFE_BMP180.h>
// }}}
// {{{ Variables
boolean dosetup;
int DATA_INT;
char DATA_CHAR[10];
char TOPIC[10];
char JSON[80];
String json;
// }}}
// {{{ SFE_BMP180 barometric pressure sensor
SFE_BMP180 pressure;
// altitude of the sensor station in meters
#define ALTITUDE 8.0
char status;
double T,P,p0,a;
// }}}
// {{{ Temperature Sensor DS18B20
// Data wire is plugged into port 7 on the Arduino
#define ONE_WIRE_BUS 7
// Setup a oneWire instance to communicate with any OneWire devices (not just Maxim/Dallas temperature ICs)
OneWire oneWire(ONE_WIRE_BUS);
// Pass our oneWire reference to Dallas Temperature.
DallasTemperature sensors(&oneWire);
// }}}
// {{{ DHT22 sensor
#define dht_dpin A0
dht DHT;
// }}}
// {{{ Light
#define light_pin A1
// }}}
// {{{ Timer setup
long PREVIOUS_TIME = 0;
const long INTERVAL = 60000;
// }}}
// {{{ Networking
// MQTT server
byte server[] = {192,168,1,103};
// MQTT client - this node's IP address
byte ip[] = {192,168,1,112};
// MAC address
byte mac[] = {0xFE,0xED,0xDE,0xAD,0xBF,0xFF};
// }}}
// {{{ MQTT
// MQTT message buffer
//char message_buff[10];

// MQTT callback
void callback(char* topic, byte* payload, unsigned int length);

// MQTT PubSub client
EthernetClient ethClient;
PubSubClient client(server, 1883, callback, ethClient);

// MQTT callback function
void callback(char* topic, byte* payload, unsigned int length) {
  // Convert payload to string
  //int i = 0;
  //for(i=0; i&lt;length; i++) {
  //  message_buff[i] = payload[i];
  //}
  //message_buff[i] = '\0';
  //String msg = String(message_buff);
  //String cmd = String(splitCommand(msg, '/'));
  //String command = String(cmd[0]);
  //String command_value = String(cmd[1]);
  // XXX implement commands and msg from MQTT server below
}
// }}}
// {{{ setup()
void setup() {
  dosetup = false;
  // Start up the one-wire sensors library
  sensors.begin();
  // Start the node at the IP address
  Ethernet.begin(mac, ip);
  // Start MQTT client,
  client.connect("garden");
  // Start barometric pressure sensor
  pressure.begin();
}
// }}}
// {{{ freeRam()
int freeRam () {
  extern int __heap_start, *__brkval;
  int v;
  return (int) &v - (__brkval == 0 ? (int) &__heap_start : (int) __brkval);
}
// }}}
// {{{ Loop
void loop() {
  unsigned long current_time = millis();

  // Start MQTT client
  client.loop();

  if(current_time &lt; 23000) {
    // when the millis() buffer overflows,
    // reset also PREVIOUS_TIME
    if(PREVIOUS_TIME > 230000) {
      PREVIOUS_TIME = 0;
    }
    // init
    if(dosetup == false) {
      client.publish("/h/s","garden:up");
      publishToMQTT();
      dosetup = true;
      if(PREVIOUS_TIME == 0) {
        PREVIOUS_TIME = current_time;
      }
    }
  }

  if(current_time - PREVIOUS_TIME > INTERVAL)  {
    PREVIOUS_TIME = current_time;
    publishToMQTT();
  }
}
// }}}
// {{{ publishToMQTT()
void publishToMQTT() {
  publishDHT22();
  publishLight();
  publishPressure();
  client.publish("/h/s","garden:published");
}
// }}}
// {{{ publishPressure
void publishPressure() {
  status = pressure.startTemperature();
  if (status != 0)
  {
    // XXX FIXME DO NOT use delay() Wait for the measurement to complete:
    delay(status);
    status = pressure.getTemperature(T);
    if (status != 0)
    {
      status = pressure.startPressure(3);
      if (status != 0)
      {
        // Wait for the measurement to complete:
        delay(status);
        status = pressure.getPressure(P,T);
        if (status != 0)
        {
          String data = "{\"a\":";
          dtostrf(P, 2, 2, DATA_CHAR);
          data += DATA_CHAR;
          data += ", \"r\":";
          p0 = pressure.sealevel(P,ALTITUDE); // 8 meters, TT, NZ
          dtostrf(p0, 2, 2, DATA_CHAR);
          data += DATA_CHAR;
          data += ", \"alt\":";
          a = pressure.altitude(P,p0);
          dtostrf(a, 2, 2, DATA_CHAR);
          data += DATA_CHAR;
          data += "}";
          publishJSON("/h/g/p", "p", data, "BMP180");
        }
      }
    }
  }
}
// }}}
// {{{ publishLight
void publishLight() {
  String light_value = String(analogRead(light_pin), DEC);
  json = getJSON("l", light_value, "K853518");
  json.toCharArray(JSON, 100);
  client.publish("/h/g/l", JSON);
}
// }}}
// {{{ publishDHT22
void publishDHT22() {
  DHT.read22(dht_dpin);
  publishDHT();
}
// }}}
// {{{ publishDHT
void publishDHT() {
  // dht22 temperature
  dtostrf(DHT.temperature, 2, 2, DATA_CHAR);
  json = getJSON("t", DATA_CHAR, "DHT22");
  json.toCharArray(JSON, 100);
  client.publish("/h/g/t", JSON);
  // dht22 humidity
  dtostrf(DHT.humidity, 2, 2, DATA_CHAR);
  json = getJSON("h", DATA_CHAR, "DHT22");
  json.toCharArray(JSON, 100);
  client.publish("/h/g/h", JSON);
  // dht22 dewpoint
  dtostrf(dewPoint(DHT.temperature, DHT.humidity), 2, 2, DATA_CHAR);
  json = getJSON("dp", DATA_CHAR, "DHT22");
  json.toCharArray(JSON, 100);
  client.publish("/h/g/dp", JSON);
}
// }}}
// {{{ publishJSON(String topic, String key, String value, String source)
void publishJSON(String topic, String key, String value, String source) {
  json = getJSON(key, value, source);
  json.toCharArray(JSON, 100);
  topic.toCharArray(TOPIC, 30);
  client.publish(TOPIC,JSON);
}
// }}}
// {{{ getJSON(String key, String value, String source) {
String getJSON(String key, String value, String source) {
  String j = "{\"";
  j += key;
  j += "\": ";
  j += value;
  j += ", \"s\": \"";
  j += source;
  j += "\"}";
  return j;
}
// }}}
// {{{ dewPoint(double celsius, double humidity)
double dewPoint(double celsius, double humidity) {
  // (1) Saturation Vapor Pressure = ESGG(T)
  double RATIO = 373.15 / (273.15 + celsius);
  double RHS = -7.90298 * (RATIO - 1);
  RHS += 5.02808 * log10(RATIO);
  RHS += -1.3816e-7 * (pow(10, (11.344 * (1 - 1/RATIO ))) - 1) ;
  RHS += 8.1328e-3 * (pow(10, (-3.49149 * (RATIO - 1))) - 1) ;
  RHS += log10(1013.246);
  // factor -3 is to adjust units - Vapor Pressure SVP * humidity
  double VP = pow(10, RHS - 3) * humidity;
  // (2) DEWPOINT = F(Vapor Pressure)
  double T = log(VP/0.61078);   // temp var
  return (241.88 * T) / (17.558 - T);
}
// }}}