Inconsistent SD saving

Other Hardware Storage
1

I'm using a micro SD for a sensor, and I'm recording the data for an hour. Sometimes the data saves, and sometimes it doesn't, with no changes to the code or hardware. Is there any way I can fix this? It's really annoying. I'm using a DFRobot MicroSD Card Module For Arduino, and a few other sensors. It always recognises the SD card as well, but I'll check afterwards and its just an empty file sometimes.

#include <Arduino.h>
#include <SensirionI2CSen5x.h>
#include <Wire.h>
#include <SD.h>
#include <SPI.h>
#include <LiquidCrystal_I2C.h>
#include <dht.h>

LiquidCrystal_I2C lcd(0x27,20,4);
File myFile;
const int chipselect = 4;

dht DHT;
#define DHT11_PIN 7

// The used commands use up to 48 bytes. On some Arduino's the default buffer
// space is not large enough
#define MAXBUF_REQUIREMENT 48

#if (defined(I2C_BUFFER_LENGTH) &&                 \
     (I2C_BUFFER_LENGTH >= MAXBUF_REQUIREMENT)) || \
    (defined(BUFFER_LENGTH) && BUFFER_LENGTH >= MAXBUF_REQUIREMENT)
#define USE_PRODUCT_INFO
#endif
int timer=0;

SensirionI2CSen5x sen5x;
float massConcentrationPm1p0;
float massConcentrationPm2p5;
float massConcentrationPm4p0;
float massConcentrationPm10p0;
float ambientHumidity;
float ambientTemperature;
float vocIndex;
float noxIndex;

void setup() {
    lcd.init();
    lcd.backlight();
    Serial.begin(115200);
    while (!Serial) {
        delay(100);
    }
    lcd.clear();
    if (SD.begin(chipselect)){
      lcd.println("SD card accepted");
    }else{
      lcd.println("SD card missing or rejected");
      while(1);
    }
    delay(1000);
    lcd.clear();
    myFile =SD.open("RESULTS.TXT", FILE_WRITE);
    if (myFile){
      lcd.print("Wrting headers to csv");
      myFile.println("\n------------------NEW TEST-----------------");
      myFile.print("pm1,pm2.5,pm4,pm10,temp,humid\n");
    }else{
      lcd.print("Error opening csv");
    }
    delay(1000);
    Wire.begin();

    sen5x.begin(Wire);
    sen5x.deviceReset();
    sen5x.setTemperatureOffsetSimple(0);
    // Start Measurement
    sen5x.startMeasurement();
}

void loop() {
    delay(1000);
    timer++;

    if (timer<=3600){
    // Read Measurement
      sen5x.readMeasuredValues(
          massConcentrationPm1p0, massConcentrationPm2p5, massConcentrationPm4p0,
          massConcentrationPm10p0, ambientHumidity, ambientTemperature, vocIndex,
          noxIndex);
      int chk =DHT.read11(DHT11_PIN);
      String temp=String(massConcentrationPm1p0)+","+String(massConcentrationPm2p5)+","+String(massConcentrationPm4p0)+","+String(massConcentrationPm10p0)+","+String(DHT.temperature)+","+String(DHT.humidity)+"\n";
      myFile.print(temp);

      lcd.clear();
      lcd.setCursor(0,0);
      lcd.print("PM1:");
      lcd.setCursor(9,0);
      lcd.print("PM25:");
      lcd.setCursor(0,1);
      lcd.print("PM4:");
      lcd.setCursor(9,1);
      lcd.print("PM10:");
      lcd.setCursor(0,2);
      lcd.print("Temp:");
      lcd.setCursor(11,2);
      lcd.print("Hum.:");
      lcd.setCursor(4,0);
      lcd.print(String(massConcentrationPm1p0));
      lcd.setCursor(14,0);
      lcd.print(String(massConcentrationPm2p5));
      lcd.setCursor(4,1);
      lcd.print(String(massConcentrationPm4p0));
      lcd.setCursor(13,1);
      lcd.print(String(massConcentrationPm10p0));
      lcd.setCursor(5,2);
      lcd.print(DHT.temperature);
      lcd.setCursor(16,2);
      lcd.print(DHT.humidity);
      lcd.setCursor(0,3);
      lcd.print("Datapoint:");
      lcd.print(timer);
    }else{
      myFile.close();
      lcd.clear();
      lcd.setCursor(0,0);
      lcd.println("Please eject");
      lcd.setCursor(1,0);
      lcd.println("the SD Card");
      lcd.println("Experiment complete!");
      delay(1000000);
    }
    }
2

The most obvious piece of advice I would give you is to avoid using the String data type if you are using a microcontroller with limited amounts of RAM.

Try using ordinary c strings instead. You can use the sprintf function to do formatted print to a small char buffer before printing to a file.

3

Which Arduino are you using? Especially on AVR-based MCUs Uno, Mega and similar), use of String objects leads to memory problems and program crashes.

This:

      String temp=String(massConcentrationPm1p0)+","+String(massConcentrationPm2p5)+","+String(massConcentrationPm4p0)+","+String(massConcentrationPm10p0)+","+String(DHT.temperature)+","+String(DHT.humidity)+"\n";
      myFile.print(temp);

Should be replaced with the following, and your program will be smaller and faster:

myFile.print(massConcentrationPm1p0);
myFile.print(",");
myFile.print(massConcentrationPm2p5);
myFile.print(",");
// .etc

By the way, it is a common observation that with Arduino, data storage on SD cards is problematic and error prone, compared to implementations on other platforms, like Raspberry Pi.

4

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