Reading text from sd card is returning weird characters?

Kara 08/17/2018. 1 answers, 99 views
lcd sd-card display

I have an ebook which is converted to a .txt file saved on an sd card which is connected to the arduino. I'm trying to display the words from the book on a 16x2 lcd display on word at a time. It works mostly except when it reads a word that has an apostrophe or a pipe symbol it does not display correctly to the lcd display or the serial output.

For example the word "author's" will be displayed as "authorâs" (edit: there is actually two boxes between the "â" and the s that is not displaying on this forum) on both the lcd display and serial output.

I've spent an entire day now with this one problem hopefully there is a mistake someone can pick up on :/

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

const int chipSelect = 53;

const int rs = 12, en = 11, d4 = 5, d5 = 4, d6 = 3, d7 = 2;
LiquidCrystal lcd(rs, en, d4, d5, d6, d7);

char nextChar;
String wordBuffer = "";

void setup() {

  lcd.begin(16, 2);

  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.");

  // 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");


  if (dataFile) {
    while (dataFile.available()) {

      nextChar = dataFile.read();
      
      if (isWhitespace(nextChar)){

        lcd.print(wordBuffer);

        Serial.println(wordBuffer);

        lcd.display();

        delay(500);

        wordBuffer = "";
        lcd.clear();

      }
      else{

        wordBuffer = wordBuffer + nextChar;
        wordBuffer.trim();
      }
      
    }
    dataFile.close();
  }

  // if the file isn't open, pop up an error:
  else {
    Serial.println("error opening datalog.txt");
  }
}

void loop() {
}

1 Answers


Majenko 08/17/2018.

The text file is not ASCII, it is UTF-8. You will either have to convert it to pure ASCII, or write (or obtain) a conversion routine to approximate the UTF-8 characters using ASCII on the Arduino.

Maybe this can help you.


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