樹莓派 & 試算表 = Free Data Logger

上一篇「讓 Respberry Pi 告訴你溫濕度(DHT11) 」已經可以成功取得溫濕度的資訊，但是要如何利用免費的資源去記錄下這些資訊？

而本篇將實作這個功能，只要稍稍擴充前一篇中的監聽程式，加上 "DHT Humidity Sensing on Raspberry Pi with GDocs Logging" 裡的程式 "Adafruit_DHT_googledocs.ex. py"，讓 Raspberry Pi （RPi）可以自動連結 google 雲端試算表，並且記錄溫濕度、露點等等於試算表中。

等同於擁有一個個人而且免費的雲端 Data Logger，只要連接一些適當的感應器，再加上低功耗的 RPi，就可以記錄周遭微氣候的變化。

Arduino
Arduino程式跟上一篇的 PART I 幾乎相同，只有多了一個 Serial.flush 指令，用來清空緩衝區的數值，以及延長等待時間至 20 秒。
燒錄程式之前，記得先把 "DHT11-Humidity-TempSensor" 網頁底下的 DHT11.zip 加到 Sketch 的函式庫（library）中。

Sketch code：

/* YourDuino.com Example Software Sketch
   DHT11 Humidity and Temperature Sensor test
   Credits: Rob Tillaart
   http://arduino-direct.com/sunshop/index.php?l=product_detail&p=162
   terry@yourduino.com */
   
/*-----( Import needed libraries )-----*/
#include 

/*-----( Declare objects )-----*/
dht11 DHT11;

/*-----( Declare Constants, Pin Numbers )-----*/
#define DHT11PIN 2

void setup()   /*----( SETUP: RUNS ONCE )----*/
{
  Serial.begin(9600);
}/*--(end setup )---*/

void loop()   /*----( LOOP: RUNS CONSTANTLY )----*/
{
   Serial.println("\n");

  int chk = DHT11.read(DHT11PIN);

  Serial.print("Read sensor: ");
  switch (chk)
  {
    case 0: Serial.println("OK"); break;
    case -1: Serial.println("Checksum error"); break;
    case -2: Serial.println("Time out error"); break;
    default: Serial.println("Unknown error"); break;
  }

  Serial.print("Humidity (%): ");
  Serial.println((float)DHT11.humidity, 2);

  Serial.print("Temperature (oC): ");
  Serial.println((float)DHT11.temperature, 2);

  Serial.print("Temperature (oF): ");
  Serial.println(Fahrenheit(DHT11.temperature), 2);

  Serial.print("Temperature (K): ");
  Serial.println(Kelvin(DHT11.temperature), 2);

  Serial.print("Dew Point (oC): ");
  Serial.println(dewPoint(DHT11.temperature, DHT11.humidity));

  Serial.print("Dew PointFast (oC): ");
  Serial.println(dewPointFast(DHT11.temperature, DHT11.humidity));

  Serial.flush();
  delay(20000);
}/* --(end main loop )-- */

/*-----( Declare User-written Functions )-----*/
//
//Celsius to Fahrenheit conversion
double Fahrenheit(double celsius)
{
        return 1.8 * celsius + 32;
}

//Celsius to Kelvin conversion
double Kelvin(double celsius)
{
        return celsius + 273.15;
}

// dewPoint function NOAA
// reference: http://wahiduddin.net/calc/density_algorithms.htm 
double dewPoint(double celsius, double humidity)
{
        double A0= 373.15/(273.15 + celsius);
        double SUM = -7.90298 * (A0-1);
        SUM += 5.02808 * log10(A0);
        SUM += -1.3816e-7 * (pow(10, (11.344*(1-1/A0)))-1) ;
        SUM += 8.1328e-3 * (pow(10,(-3.49149*(A0-1)))-1) ;
        SUM += log10(1013.246);
        double VP = pow(10, SUM-3) * humidity;
        double T = log(VP/0.61078);   // temp var
        return (241.88 * T) / (17.558-T);
}

// delta max = 0.6544 wrt dewPoint()
// 5x faster than dewPoint()
// reference: http://en.wikipedia.org/wiki/Dew_point
double dewPointFast(double celsius, double humidity)
{
        double a = 17.271;
        double b = 237.7;
        double temp = (a * celsius) / (b + celsius) + log(humidity/100);
        double Td = (b * temp) / (a - temp);
        return Td;
}

/* ( THE END ) */

輸出格式

Raspberry Pi
從 Arduino 送出溫濕度以及相關的數據到 google 試算表這中間，需要由 RPi 擔任閘道（gateway）的角色，由 "Connecting to Google Docs" 一文，可以知道這部份的工作，大略分為三個部分：

Gspread
首先必須先安裝 Gspread 函式庫，就可以輕鬆的以寫好的函式登入 google 試算表，自動把數據寫到裡面。

pi@raspberrypi ~ $ wget http://pypi.python.org/packages/source/g/gspread/gspread-0.0.13.tar.gz#md5=d413ad08805f3f0a1e9d5f9bebe5d35b
pi@raspberrypi ~ $ tar -zxvf gspread-0.0.13.tar.gz
pi@raspberrypi ~ $ cd gspread-0.0.13
pi@raspberrypi ~ $ sudo python setup.py install

python 程式
程式很簡短也不難，首先需先填入 google 帳戶資料以登入連結雲端文件。使用第一個 while 迴圈清除掉 Arduino 丟回來的第一筆不規則資料，第二個 while 迴圈讀取數據並使用 re.search 擷取所需要的數據資料，最後這裡把 Sensor 狀態、溫濕度（攝氏、華氏）、露點丟到試算表上頭。

google 試算表
建立試算表，填入抬頭，並刪掉以下所有得儲存格，程式丟出數據後會自動新增儲存格，而且要注意兩次輸入間隔不要小於兩秒，否則會被擋掉。

python code：

import serial
import time
import re
import subprocess
import sys
import datetime
import gspread
# ===========================================================================
# Google Account Details
# ===========================================================================

# Account details for google docs
email       = 'google帳號'
password    = ''
spreadsheet = '試算表名稱'

# ===========================================================================
# Example Code
# ===========================================================================


# Login with your Google account
try:
  gc = gspread.login(email, password)
except:
  print "Unable to log in.  Check your email address/password"
  sys.exit()

# Open a worksheet from your spreadsheet using the filename
try:
  worksheet = gc.open(spreadsheet).sheet1
  # Alternatively, open a spreadsheet using the spreadsheet's key
  # worksheet = gc.open_by_key('0BmgG6nO_6dprdS1MN3d3MkdPa142WFRrdnRRUWl1UFE')
except:
  print "Unable to open the spreadsheet.  Check your filename: %s" % spreadsheet
  sys.exit()


# Set Channel 
ser = serial.Serial('/dev/ttyACM0', 9600)

# buffer clear
start_time = time.time()
while 1 :
    output = ser.readline()
    print output
    
    if time.time() - start_time > 15:
     print time.time() - start_time
     break

# Reading sensor data
while 1 :
    output = ser.readline()
    match = re.search("sensor\:\s(\w+)", output)
    if match:
        status = match.group(1)
#        print match.group(1)
        continue
        
    match = re.search("Humidity\s\(\%\)\:\s(\d+)", output)
    if match:
        Humidity = float(match.group(1))
#        print "Humidity:",Humidity
        continue
    
    match = re.search("Temperature\s\(oC\)\:\s(\d+)", output)
    if match:
        TempC = float(match.group(1))
#       print "Temp:", float(match.group(1)),"oC"
        continue

    match = re.search("Temperature\s\(oF\)\:\s(\d+)", output)    
    if match:
        TempF = float(match.group(1))
#        print "Temp:", float(match.group(1)),"oF"
        continue   
    
    match = re.search("Temperature\s\(K\)\:\s(\d+)", output)    
    if match:
        TempK = float(match.group(1))
#        print "Temp:", float(match.group(1)),"K"
        continue  
    
    match = re.search("Dew\sPoint\s\(oC\)\:\s(\d+)", output)    
    if match:
        Dew = float(match.group(1))
#        print "Dew:", float(match.group(1)),"oC"
        continue  
    
    match = re.search("Dew\sPointFast\s\(oC\)\:\s(\d+)", output)    
    if match:
        DewFast = float(match.group(1))
#        print "Dew PointFast:", float(match.group(1)),"oC"
    else:
        continue
# Insert data    
    try:
        values = [datetime.datetime.now(), status, Humidity, TempC, TempF, TempK, Dew, DewFast]
        worksheet.append_row(values)
    except:
        print "Unable to append data.  Check your connection?"
        sys.exit()
    
#    print status, Humidity, TempC, TempF, TempK, Dew, DewFast
    time.sleep(0.5)

不過本篇的程式做法並不符合效率，如果需要承接的感測值太多，實際上會盡量讓前端 Arduino 輸出的資料格式更為精簡，使 RPi 以最少的循環次數讀完所有值，一方面可以加速執行效率，另一方面則降低能量的耗損。

最後下圖就是以試算表內製作圖表的功能，所繪製的溫濕度圖，不訪試著變動解析度，來觀察這兩天（3/16 ~ 3/17）房間內溫濕度的變化。

Fresh Meat

網頁

2013年3月17日星期日