microSD shield issues

Other Miscellaneous
1

Hello, right off the bat let me admit I’m relatively - very - new to using Arduinos. The SparkFun tutorials work well and I appreciate all of the resources SparkFun has provided online.

We are trying to measure temperature using a TMP36 and write the data to the card in the microSD shield. We’re running it with a SparkFun Redboard. The temperatures and timestamp show up flawlessly in the serial monitor. However, the data that writes to the card isn’t the same as what we’re seeing in the serial monitor. The datalog on the SD card has many more data points that all seem to hover around one value - as if it’s reading an almost-constant temperature, when we know that’s not the case.

First, we’re uploading this code:

/*
  SD card test

  created  28 Mar 2011
  by Limor Fried
  modified 9 Apr 2012
  by Tom Igoe

  Hookup for the SparkFun microSD shield 
  on a SparkFun RedBoard/Arduino Uno R3

  MOSI - 11
  MISO - 12
  CLK - 13 
  CS - 8
*/

// include the SD library:
#include <SPI.h>
#include <SD.h>

// set up variables using the SD utility library functions:
Sd2Card card;
SdVolume volume;
SdFile root;

// The Sparkfun microSD shield uses pin 8 for CS
const int chipSelect = 8;

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("\nInitializing SD card...");

  // Note that even if it's not used as the CS pin, the hardware SS pin
  // (10 on most Arduino boards, 53 on the Mega) must be left as an output
  // or the SD library functions will not work.

  pinMode(10, OUTPUT);


  // we'll use the initialization code from the utility libraries
  // since we're just testing if the card is working!
  if (!card.init(SPI_HALF_SPEED, chipSelect)) {
    Serial.println("initialization failed. Things to check:");
    Serial.println("* is a card is inserted?");
    Serial.println("* Is your wiring correct?");
    Serial.println("* did you change the chipSelect pin to match your shield or module?");
    return;
  } else {
    Serial.println("Wiring is correct and a card is present.");
  }

  // print the type of card
  Serial.print("\nCard type: ");
  switch (card.type()) {
    case SD_CARD_TYPE_SD1:
      Serial.println("SD1");
      break;
    case SD_CARD_TYPE_SD2:
      Serial.println("SD2");
      break;
    case SD_CARD_TYPE_SDHC:
      Serial.println("SDHC");
      break;
    default:
      Serial.println("Unknown");
  }

  // Now we will try to open the 'volume'/'partition' - it should be FAT16 or FAT32
  if (!volume.init(card)) {
    Serial.println("Could not find FAT16/FAT32 partition.\nMake sure you've formatted the card");
    return;
  }


  // print the type and size of the first FAT-type volume
  uint32_t volumesize;
  Serial.print("\nVolume type is FAT");
  Serial.println(volume.fatType(), DEC);
  Serial.println();

  volumesize = volume.blocksPerCluster();    // clusters are collections of blocks
  volumesize *= volume.clusterCount();       // we'll have a lot of clusters
  volumesize *= 512;                            // SD card blocks are always 512 bytes
  Serial.print("Volume size (bytes): ");
  Serial.println(volumesize);
  Serial.print("Volume size (Kbytes): ");
  volumesize /= 1024;
  Serial.println(volumesize);
  Serial.print("Volume size (Mbytes): ");
  volumesize /= 1024;
  Serial.println(volumesize);


  Serial.println("\nFiles found on the card (name, date and size in bytes): ");
  root.openRoot(volume);

  // list all files in the card with date and size
  root.ls(LS_R | LS_DATE | LS_SIZE);
}


void loop(void) {

}

Next, we’re sending over this sketch to measure the temperature:

/******************************************************************
 SparkFun Inventor's Kit
 Example sketch 07 - TEMPERATURE SENSOR
  Use the "serial monitor" window to read a temperature sensor.
  The TMP36 is an easy-to-use temperature sensor that outputs
  a voltage that's proportional to the ambient temperature.
  You can use it for all kinds of automation tasks where you'd
  like to know or control the temperature of something.
  More information on the sensor is available in the datasheet:
  http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Sensors/Temp/TMP35_36_37.pdf
  Even more exciting, we'll start using the Arduino's serial port
  to send data back to your main computer! Up until now, we've
  been limited to using simple LEDs for output. We'll see that
  the Arduino can also easily output all kinds of text and data.
This sketch was written by SparkFun Electronics,
with lots of help from the Arduino community.
This code is completely free for any use.
Visit http://learn.sparkfun.com/products/2 for SIK information.
Visit http://www.arduino.cc to learn about the Arduino.
Version 2.0 6/2012 MDG
******************************************************************/


// We'll use analog input 0 to measure the temperature sensor's
// signal pin.

const int temperaturePin = A0;


void setup()
{

    Serial.begin(9600); //Initialize serial port & set baud rate to 9600 bits per second (bps)
}


void loop()
{


    float voltage, degreesC, degreesF; //Declare 3 floating point variables

    voltage = getVoltage(temperaturePin); //Measure the voltage at the analog pin

    degreesC = (voltage - 0.4809) / 0.0099; // Convert the voltage to degrees Celsius

    degreesF = degreesC * (9.0 / 5.0) + 32.0; //Convert degrees Celsius to Fahrenheit

    //Now print to the Serial monitor. Remember the baud must be 9600 on your monitor!
    // These statements will print lines of data like this:
    // "voltage: 0.73 deg C: 22.75 deg F: 72.96"

    Serial.print("voltage: ");
    Serial.print(voltage);
    Serial.print("  deg C: ");
    Serial.print(degreesC);
    Serial.print("  deg F: ");
    Serial.println(degreesF);

    delay(1000); // repeat once per second (change as you wish!)
}


float getVoltage(int pin)   //Function to read and return
                            //floating-point value (true voltage)
                            //on analog pin 
{

    return (analogRead(pin) * 0.004882814); 
    // This equation converts the 0 to 1023 value that analogRead()
    // returns, into a 0.0 to 5.0 value that is the true voltage
    // being read at that pin.
}

// Other things to try with this code:

//   Turn on an LED if the temperature is above or below a value.

//   Read that threshold value from a potentiometer - now you've
//   created a thermostat!

Any help you can provide will be most welcome! The students’ goal is to measure & record temperatures at high altitudes, from the payload of a weather balloon. We chose Arduinos for this task because they’re much lighter than our other equipment.

2

Sorry. Can’t understand one thing. Which part of the code are you using to write data to the sd card?

3

Thanks for responding. I goofed on my first cut/paste above. The sketch we’re trying to use to write data to the SD card is this one:

/*
  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 4 (for MKRZero SD: SDCARD_SS_PIN)

  created  24 Nov 2010
  modified 9 Apr 2012
  by Tom Igoe

  This example code is in the public domain.

*/

#include <SPI.h>
#include <SD.h>

const int chipSelect = 8;

void setup() {
  // Open serial communications and wait for port to open:
  Serial.begin(9600);
  while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB port 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:
    while (1);
  }
  Serial.println("card initialized.");
}

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

  // read three sensors and append to the string:
  for (int analogPin = 0; analogPin < 3; analogPin++) {
    int sensor = analogRead(analogPin);
    dataString += String(sensor);
    if (analogPin < 2) {
      dataString += ",";
    }
  }

  // open the file. note that only one file can be open at a time,
  // so you have to close this one before opening another.
  File dataFile = SD.open("datalog.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 datalog.txt");
  }
}
4

You have CS on 2 different pins inside your sketch. (Pin 4 and pin 8)

Fix that and see if it helps.