Arduino Projects of note/datalogger sdcard

finally it works!

datalogger_sdcard.ino

/*
  SD card datalogger

 This example shows how to log data from three analog sensors
 to an SD card using the SD library.

 The circuit:
 * analog sensors on analog ins 0, 1, and 2
 * SD card attached to SPI bus as follows:
 ** MOSI - pin 11
 ** MISO - pin 12
 ** CLK - pin 13
 ** CS - pin 10

 created  24 Nov 2010
 modified 9 Apr 2012
 by Tom Igoe

 This example code is in the public domain.

 */

#include <DS3231.h>
#include <SPI.h>
#include <SD.h>
#include <Wire.h>
#include "HTU21D.h"

HTU21D myHumidity;
DS3231 Clock;
bool Century=false;
bool h12;
bool PM;
byte ADay, AHour, AMinute, ASecond, ABits;
bool ADy, A12h, Apm;
byte year, month, date, DoW, hour, minute, second;

const int chipSelect = 4;
String txtfilename = "datalog.txt";  
File myFile;

String ReadDS3231() {
 String ds = "";
 
 int second,minute,hour,date,month,year,temperature;
 second=Clock.getSecond();
 minute=Clock.getMinute();
 hour=Clock.getHour(h12, PM);
 date=Clock.getDate();
 month=Clock.getMonth(Century);
 year=Clock.getYear();

 temperature=Clock.getTemperature();

 ds += "20";
 ds += year;
 ds += "-";
 ds += month;
 ds += "-";
 ds += date;
 ds += " ";
 ds += hour;
 ds += ":";
 ds += minute;
 ds += ":";
 ds += second;
 ds += " clock temp:";
 ds += temperature;
 
 return ds;
 
}

void setup() {
  // Open serial communications and wait for port to open:
  Serial.begin(9600);
  while (!Serial) {
    ; // wait for serial port to connect. Needed for Leonardo only
  }

  Serial.print("Initializing SD card...");

  // see if the card is present and can be initialized:
  if (!SD.begin(chipSelect)) {
    Serial.println("Card failed, or not present");
    // don't do anything more:
    return;
  }
  Serial.println("card initialized.");
  myHumidity.begin();
  Serial.println("HTU21D initialized");
}

void loop() {
  
  delay(360000);
  
  // make a string for assembling the data to log:
  String dataString = "";

  //HTU21D
  float humd = myHumidity.readHumidity();
  float temp = myHumidity.readTemperature();

  //RTC
  String ds;
  ds = ReadDS3231();
  
  dataString += "time: ";
  dataString += ds;  
  dataString += " hum: ";
  dataString += humd;
  dataString += " temp: ";
  dataString += temp;  

  // open the file. note that only one file can be open at a time,
  // so you have to close this one before opening another.

  if (SD.exists("datafile.txt")) {
    // Serial.println("datafile.txt exists.");
  }
  else {
    Serial.println("datafile.txt doesn't exist. creating");
    // open a new file and immediately close it:
    Serial.println("Creating datafile.txt...");
    myFile = SD.open("datafile.txt", FILE_WRITE);
    myFile.close();
  }

  // Check to see if the file exists: 
  if (SD.exists("datafile.txt")) {
    // Serial.println("datafile.txt exists.");
  }
  else {
    Serial.println("datafile.txt doesn't exist.");  
  }
  
  File dataFile = SD.open("datafile.txt", FILE_WRITE);

  // if the file is available, write to it:
  if (dataFile) {
    dataFile.println(dataString);
    dataFile.close();
    // print to the serial port too:
    Serial.println(dataString);
  }
  // if the file isn't open, pop up an error:
  else {
    Serial.println("error opening datafile.txt");
  }
}

Python style: Htu21d.py