Weatherstation - Receiving the data

In a previous post, I went over how the weatherstation data will be accessed--an Arduino-based webserver. However, this implementation had a major limitation: no data logging or visualization. I decided to switch to uploading the received data to Xively, which provides the data logging and visualization.

Receiver Hardware

I added a protoshield on top of the Ethernet shield. The protoshield has the 433 MHz receiver soldered onto it.

Show Code

// Author: Zac DeMeo
// Uses VirtualWire to receive transmissions of weather data. Sends data to Xively for logging. 

#include <Xively.h>
#include <HttpClient.h>
#include <VirtualWire.h>
#include <Ethernet.h>
#include <SPI.h>  

#define RX_PIN 7
#define RX_RATE 500
#define DELAY 3600 
#define FEEDID YOUR_FEED_ID

// Time
unsigned long mark = 0;

// Ethernet shield
byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED }; // Arduino Ethernet shield MAC
EthernetClient xivelyEthernetClient;

// Xively channel key and IDs  
const char xivelyKey[] = YOUR_XIVELY_KEY;
char tempID[] = "Temperature";
char presID[] = "Pressure";
char rhID[] = "Relative_Humidity";
char dewpointID[] = "Dewpoint";
char voltID[] = "Battery_Voltage";
char hiID[] = "Heat_Index";

// Define the strings for our datastream IDs
XivelyDatastream datastreams[] = {
  XivelyDatastream(tempID, strlen(tempID), DATASTREAM_FLOAT),
  XivelyDatastream(presID, strlen(presID), DATASTREAM_FLOAT),
  XivelyDatastream(rhID, strlen(rhID), DATASTREAM_FLOAT),
  XivelyDatastream(dewpointID, strlen(dewpointID), DATASTREAM_FLOAT),
  XivelyDatastream(voltID, strlen(voltID), DATASTREAM_FLOAT),
  XivelyDatastream(hiID, strlen(hiID), DATASTREAM_FLOAT)
};
// Create feed
XivelyFeed feed(FEEDID, datastreams, 6);
XivelyClient xivelyClient(xivelyEthernetClient);

// Weather data
// Index 0: Relative humidity (%)
// Index 1: Temperature (F)
// Index 2: Estimated dewpoint (F)
// Index 3: Barometric pressure (inHg)
// Index 4: Vcc on weatherstation (V)
char values[5][8];

void setup() {
  vw_setup(RX_RATE);
  vw_set_rx_pin(RX_PIN);  
  vw_rx_start(); 
  getIPAddress();
}

void loop() {
  listenForTx();
  
  // Re-establish connection with router every hour
  if (millis() - mark >= DELAY) {
    getIPAddress();
    mark = millis();
  }
}

// Get IP address using DHCP
void getIPAddress() {
  int connection;
  do {
    connection = Ethernet.begin(mac);
  } while (connection == 0);
}

void listenForTx() {
  uint8_t buf[VW_MAX_MESSAGE_LEN];
  uint8_t buflen = VW_MAX_MESSAGE_LEN;

  if (vw_get_message(buf, &buflen)) {
    char message[30];     // String to copy buf into
    message[0] = '\0';
   
    // Check if transmission is valid. If all sensors have returned data, message will have 4 "," characters
    // If there are not 4 commas, return without parsing data and wait for next transmission
    int k = 0;
    for (int i = 0; i < buflen; i++) {
      if (buf[i] == ',') {
        k++;  
      }
    } 
    if (k != 4) {
     return;
    }
    
    // Read buffer into string and split at each ","
    int j = 0;
    for (int i = 0; i < buflen; i++) {
      if (buf[i] != ',') {
        int length = strlen(message);
        message[length] = buf[i];
        message[length + 1] = '\0';      
        if (i == (buflen - 1)) {
          strcpy(values[j], message);
          break;
        }  
      } 
      else {
        strcpy(values[j], message);
        message[0] = '\0';
        j++;
      }
    }   
    // Log data to Xively
    logData();
  }
}

void logData() {
  float rh = atof(values[0]);
  float t = atof(values[1]);
  float dp = atof(values[2]);
  float p = atof(values[3]);
  float v = atof(values[4]);
  float hi = heatIndex(t, rh);
  
  // Add sensor values to datastream
  datastreams[0].setFloat(t);
  datastreams[1].setFloat(p);
  datastreams[2].setFloat(rh);
  datastreams[3].setFloat(dp);
  datastreams[4].setFloat(v);
  datastreams[5].setFloat(hi);
  
  // Send data to Xively
  int retval = xivelyClient.put(feed, xivelyKey);
  
  // Something's wrong with our connection
  // Try to establish a connection with the router
  if (retval < 0) {   
    getIPAddress();
  } 
}

// Uses NOAA heat index calculation from http://www.hpc.ncep.noaa.gov/html/heatindex_equation.shtml
float heatIndex(float t, float rh) {
  float hi;
  
  // First, calculate simple index
  hi = 0.5 * (t + 61.0 + ((t-68.0)*1.2) + (rh*0.094));
  hi = 0.5*(hi + t);
  
  // When the heat index is >80 F, calculate using alternative method
  if (hi >= 80) {
    hi = -42.379 + 2.04901523*t + 10.14333127*rh - .22475541*t*rh - .00683783*t*t - .05481717*rh*rh + .00122874*t*t*rh + .00085282*t*rh*rh - .00000199*t*t*rh*rh;
    
    // When the relative humidity is <13% and temperature is [80,112] F
    if (rh < 13.0 && t >= 80.0 && t <= 112.0) {
      hi = hi - (((13-rh)/4)*sqrt((17-abs(t-95.))/17));   
    } else if (rh > 85.0 && t >= 80.0 && t <= 87.0) { // When the relative humidity is >85% and temperature is [80,112] F
      hi = hi + (((rh-85)/10) * ((87-t)/5));
    }
  } 
  
  return hi; 
}

Because the receiver is connected to a router, the router sometimes needs to be reset. Therefore, the script calls getIPAddress() every hour.