I was looking at following link (after google search); How to Write Data to Files on an SD Card With the Arduino - Circuit Basics.
He did in .txt file. where time, temperature, pressure, Altitude is reported in column format . My idea came from that link. But could not execute in my program. Here is the code he reported in that link
#include <SD.h>
#include <SPI.h>
#include <Adafruit_BMP280.h>
Adafruit_BMP280 bmp;
File myFile;
// change this to match your SD shield or module:
// Adafruit SD shields and modules: pin 10
// Sparkfun SD shield: pin 8
//mega pin = 53;
const int chipSelect = 10;
float QNH = 1022.67; //Change the "1022.67" to your current sea level barrometric pressure (https://www.wunderground.com)
const int BMP_address = 0x76;
float pressure;
float temperature;
float altimeter;
char charRead;
char runMode;
byte i=0; //counter
char dataStr[100] = "";
char buffer[7];
////////////////////////////////////////////////////
void setup()
{
Serial.begin(9600);
Serial.println("BMP280/SD Card Demo");
bmp.begin(BMP_address);
if (SD.begin(chipSelect))
{
Serial.println("SD card is present & ready");
}
else
{
Serial.println("SD card missing or failure");
while(1); //halt program
}
//clear out old data file
if (SD.exists("csv.txt"))
{
Serial.println("Removing simple.txt");
SD.remove("csv.txt");
Serial.println("Done");
}
//write csv headers to file:
myFile = SD.open("csv.txt", FILE_WRITE);
if (myFile) // it opened OK
{
Serial.println("Writing headers to csv.txt");
myFile.println("Time,Pressure,Temperature,Altitude");
myFile.close();
Serial.println("Headers written");
}
else
Serial.println("Error opening csv.txt");
Serial.println("Enter w for write, r for read or s for split csv");
}// end setup()
////////////////////////////////////////////////////////////
void loop(void)
{
dataStr[0] = 0;
pressure = bmp.readPressure()/100; //and conv Pa to hPa
temperature = bmp.readTemperature();
altimeter = bmp.readAltitude (QNH); //QNH is local sea lev pressure
//----------------------- using c-type ---------------------------
//convert floats to string and assemble c-type char string for writing:
ltoa( millis(),buffer,10); //conver long to charStr
strcat(dataStr, buffer);//add it onto the end
strcat( dataStr, ", "); //append the delimeter
//dtostrf(floatVal, minimum width, precision, character array);
dtostrf(pressure, 5, 1, buffer); //5 is mininum width, 1 is precision; float value is copied onto buff
strcat( dataStr, buffer); //append the coverted float
strcat( dataStr, ", "); //append the delimeter
dtostrf(temperature, 5, 1, buffer); //5 is mininum width, 1 is precision; float value is copied onto buff
strcat( dataStr, buffer); //append the coverted float
strcat( dataStr, ", "); //append the delimeter
dtostrf(altimeter, 5, 1, buffer); //5 is mininum width, 1 is precision; float value is copied onto buff
strcat( dataStr, buffer); //append the coverted float
strcat( dataStr, 0); //terminate correctly
//Serial.println(dataStr);
//---------------------------------------------------
//create a loop to read from the keyboard a command character
//this will be 'r' for read, 'w' for write and 'd' for delete.
if (Serial.available()) //get command from keyboard:
{
charRead = tolower(Serial.read()); //force ucase
Serial.write(charRead); //write it back to Serial window
Serial.println();
}
if(charRead == 'w') //we are logging
runMode = 'W';
if(charRead == 'r') //we are reading
runMode = 'R';
if(charRead == 'd') //we are deleting
runMode = 'D';
//----------------------------------------------------
if(runMode == 'W') //write to file
{
//----- display on local Serial monitor: ------------
Serial.print(pressure); Serial.print("hPa ");
Serial.print(temperature);
Serial.write(0xC2); //send degree symbol
Serial.write(0xB0); //send degree symbol
Serial.print("C ");
Serial.print(altimeter); Serial.println("m");
//---------------------------------------------
// open the file. note that only one file can be open at a time,
myFile = SD.open("csv.txt", FILE_WRITE);
// if the file opened okay, write to it:
if (myFile)
{
Serial.println("Writing to csv.txt");
myFile.println(dataStr);
myFile.println(dataStr);
myFile.close();
}
else
{
Serial.println("error opening csv.txt");
}
delay(1000);
}
//--------------------------------------------------
if(runMode == 'R') //we are reading
{
if (!SD.exists("csv.txt"))
Serial.println("csv.txt doesn't exist.");
Serial.println("Reading from csv.txt");
myFile = SD.open("csv.txt");
while (myFile.available())
{
char inputChar = myFile.read(); // Gets one byte from serial buffer
if (inputChar == '\n') //end of line (or 10)
{
dataStr[i] = 0; //terminate the string correctly
Serial.println(dataStr);
i=0; //reset the counter
}
else
{
dataStr[i] = inputChar; // Store it
i++; // Increment where to put next char
if(i> sizeof(dataStr)) //error checking for overflow
{
Serial.println("Incoming string longer than array allows");
Serial.println(sizeof(dataStr));
while(1);
}
}
}
}
//-------------------------------------------
if(runMode=='D')
{
//delete a file:
if (SD.exists("csv.txt"))
{
Serial.println("Removing csv.txt");
SD.remove("csv.txt");
Serial.println("Done");
}
}
//-----------------------------------------
} //end main
