Custom backend example

Author: pral2a

data/README.md

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+Smart Citizen Data
+==================
+
+**This is a basic example for creating your custom server backend for smartcitizen**
+
+*Note this is aimed at learning, not production ready code.*
+
+Check the complete documentation at http://docs.smartcitizen.me/#/start/how-to-store-data-in-your-own-database
+

data/examples/add.php

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+  <?php
+
+    /*
+
+    Smart Data - add.php
+
+    Basic example, reads SmartCitizen request and stored in a csv file.
+
+    You will need to set your end-point in the SCK firmware Constants.h (WEB[] in line 216)
+
+    Example curl:
+
+    $ curl -v -X PUT -H 'Host: data.smartcitizen.me' -H 'User-Agent: SmartCitizen' -H 'X-SmartCitizenMacADDR: 00:00:00:00:00:01' -H 'X-SmartCitizenVersion: 1.1-0.8.5-A' -H 'X-SmartCitizenData: [{"temp":"29090.6","hum":"6815.74","light":"30000","bat":"786","panel":"0","co":"112500","no2":"200000","noise":"2","nets":"10","timestamp":"2015-04-06 10:38:00"}]' 127.0.0.1/data/examples/add.php
+
+    */
+
+    include('../sck_sensor_data.php');
+    
+    $headers = getallheaders(); 
+ 
+    $data = $headers['X-SmartCitizenData'];
+  
+    $datapoints = json_decode($data, true);
+  
+    foreach ($datapoints as $datapoint) {
+      $datapoint = SCKSensorData::SCK11Convert($datapoint);
+      $csv .=  implode(', ', $datapoint);
+    }
+
+    $csv .= PHP_EOL;
+
+    file_put_contents('./data.csv', $csv, FILE_APPEND);
+
+   
+  ?>

data/examples/data.csv

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+2015-04-06 10:38:00, 25, 20, 0, 112.5, 200, 3000, 78.6, 0, 10
+2015-04-06 10:38:00, 25, 20, 0, 112.5, 200, 3000, 78.6, 0, 10
+2015-04-06 10:38:00, 25, 20, 0, 112.5, 200, 3000, 78.6, 0, 10
+2015-04-06 10:38:00, 25, 20, 0, 112.5, 200, 3000, 78.6, 0, 10

data/sck_sensor_data.php

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+<?php
+
+
+/**
+ * SCKSensorData
+ *
+ * Authors: Smart Citizen Team
+ *
+ * SCKSensorData implements all the methods necessary for calibrating 
+ * and rescaling the data received from a Smart Citizen Kit 1.1. 
+ *
+ * 
+ * TODO: Data validation based on each sensor ranges.
+ *
+ * Example usage (receive data, converted and store it in a csv file):
+ *
+ * <?php
+ *   include('../sck_sensor_data.php');
+ *   
+ *   $headers = getallheaders(); 
+ * 
+ *   $data = $headers['X-SmartCitizenData'];
+ *  
+ *   $datapoints = json_decode($data, true);
+ *  
+ *   foreach ($datapoints as $datapoint) {
+ *     $datapoint = SCKSensorData::SCK11Convert($datapoint);
+ *     $csv .=  implode(', ', $datapoint);
+ *   }
+ *
+ *   $csv .= PHP_EOL;
+ *
+ *   file_put_contents('./data.csv', $csv, FILE_APPEND);
+ * ?>
+ *
+ * SCKSensorData is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version.
+ *
+ * SCKSensorData 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 Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with SCKSensorData.  If not, see
+ * <http://www.gnu.org/licenses/>. 
+ *
+ */
+
+
+class SCKSensorData
+{
+    
+    
+    /**
+     * SCK11Calibration
+     * 
+     * Calibrates to propper SI units an SCK datapoint
+     *
+     * @param array $rawBat Indexed array containing a SCK 1.1 datapoint
+     * @return array Indexed arrary with a SCK datapoint calibrated 
+     *
+     */
+    
+    public function SCK11Convert($rawData)
+    {
+        
+        $data = array();
+        
+        if (self::isValidDateTimeString($rawData['timestamp'])) { //Check calibration....
+            
+            $data['timestamp'] = $rawData['timestamp'];
+            
+            $data['temp']  = self::tempConversion($rawData['temp']);
+            $data['hum']   = self::humConversion($rawData['hum']);
+            $data['noise'] = self::noiseConversion($rawData['noise']);
+            $data['co']    = self::coConversion($rawData['co']);
+            $data['no2']   = self::no2Conversion($rawData['no2']);
+            $data['light'] = self::lightConversion($rawData['light']);
+            $data['bat']   = self::batConversion($rawData['bat']);
+            $data['panel'] = self::panelConversion($rawData['panel']);
+            $data['nets']  = $rawData['nets'];
+            
+            return $data;
+            
+        } else {
+
+            return false;
+
+        }
+        
+    }
+    
+    /**
+     * tempConversion
+     *
+     * Temperature calibration for SHT21 based on the datasheet:
+     * https://github.com/fablabbcn/Smart-Citizen-Kit/wiki/Datasheets/HTU-21D.pdf
+     *
+     * Formula can be tune depending on the SCK enclosure.
+     * 
+     *
+     * @param float $rawTemp
+     * @return float Temperature in ºC
+     *
+     */
+    
+    public function tempConversion($rawTemp)
+    {
+        return round(-53 + 175.72 / 65536.0 * $rawTemp, 2);
+    }
+    
+    /**
+     * humConversion
+     *
+     * Humidity calibration for SHT21 based on the datasheet:
+     * https://github.com/fablabbcn/Smart-Citizen-Kit/wiki/Datasheets/HTU-21D.pdf
+     *
+     * Formula can be tune depending on the SCK enclosure.
+     * 
+     *
+     * @param float $rawHum
+     * @return float Rel. Humidity in %
+     *
+     */
+    
+    public function humConversion($rawHum)
+    {
+        return round(7 + 125.0 / 65536.0 * $rawHum, 2);
+    }
+    
+    /**
+     * noiseConversion
+     *
+     * Noise calibration for SCK1.1 sound sensor. Converts mV in to dBs. 
+     * Based on a linear regresion from a lookup table (db.json) obtained after real measurements from our test facility.
+     * 
+     *
+     * @param float $rawSound
+     * @return float noise as sound pressure in dB
+     *
+     */
+    
+    public function noiseConversion($rawSound)
+    {
+        $dbTable = json_decode(file_get_contents("./sensors/db.json"), true);
+        return round(self::tableCalibration($dbTable, $rawSound), 2);
+    }
+    
+    /**
+     * coConversion
+     *
+     * CO values rescaling. For obtaining ppm check:
+     * 
+     * @param float $rawCO
+     * @return float sensor resistance in KOhm
+     *
+     */
+    
+    public function coConversion($rawCO)
+    {
+        return round($rawCO / 1000, 2);
+    }
+    
+    /**
+     * no2Conversion
+     *
+     * NO2 values rescaling. For obtaining ppm check:
+     * 
+     * returns k0hm
+     * @param float $rawNO2
+     * @return float sensor resistance in KOhm
+     *
+     */
+    
+    public function no2Conversion($rawNO2)
+    {
+        return round($rawNO2 / 1000, 2);
+    }
+    
+    /**
+     * lightConversion
+     *
+     * Light values rescaling. 
+     * 
+     * returns lux
+     * @param float $rawLight
+     * @return float light level in lux
+     *
+     */
+    
+    public function lightConversion($rawLight)
+    {
+        return round($rawLight / 10, 2);
+    }
+    
+    /**
+     * batConversion
+     *
+     * Battery values rescaling. 
+     * 
+     * @param float $rawBat
+     * @return float battery level in %
+     *
+     */
+    
+    
+    public function batConversion($rawBat)
+    {
+        return round($rawBat / 10, 2);
+    }
+    
+    /**
+     * panelConversion
+     *
+     * Solar panel values rescaling. 
+     * 
+     * @param float $rawBat
+     * @return float Tension in volts
+     *
+     */
+    
+    public function panelConversion($rawBat)
+    {
+        return round($rawBat / 100, 2);
+    }
+    
+    /**
+     * isValidDateTimeString
+     *
+     * Check if a string is a valid time stamp
+     *
+     * @param string $str_dt
+     * @return bool
+     *
+     */
+     
+    private function isValidDateTimeString($str_dt)
+    {
+        $date1 = DateTime::createFromFormat('Y-m-d G:i:s', $str_dt);
+        $date2 = DateTime::createFromFormat('Y-m-d H:i:s', $str_dt);
+        return $date1 && ($date1->format('Y-m-d G:i:s') == $str_dt || $date2->format('Y-m-d H:i:s') == $str_dt);
+    }
+    
+     /**
+     * tableCalibration
+     *
+     * Calculates a point based on a linear regresion from a look up table
+     *
+     * @param array $refTable
+     * @param float $rawValue
+     * @return float
+     *
+     */
+    
+    private function tableCalibration($refTable, $rawValue)
+    {
+        for ($i = 0; $i < sizeof($refTable) - 1; $i++) {
+            $prevValueRef = $refTable[$i][0];
+            $nextValueRef = $refTable[$i + 1][0];
+            if ($rawValue >= $prevValueRef && $rawValue < $nextValueRef) {
+                $prevValueOutput = $refTable[$i][1];
+                $nextValueOutput = $refTable[$i + 1][1];
+                $result          = self::linearRegression($rawValue, $prevValueOutput, $nextValueOutput, $prevValueRef, $nextValueRef);
+                return $result;
+            }
+        }
+    }
+
+     /**
+     * linearRegression
+     *     *
+     * @param float $valueInput
+     * @param float $prevValueOutput
+     * @param float $nextValueOutput
+     * @param float $prevValueRef
+     * @param float $nextValueRef
+     * @return float
+     *
+     */
+
+    private function linearRegression($valueInput, $prevValueOutput, $nextValueOutput, $prevValueRef, $nextValueRef)
+    {
+        $slope  = ($nextValueOutput - $prevValueOutput) / ($nextValueRef - $prevValueRef);
+        $result = $slope * ($valueInput - $prevValueRef) + $prevValueOutput;
+        return $result;
+    }
+    
+    
+    
+}
+
+?>