Program prints weird numbers to sd card

Other Hardware Storage
1

I was creating a sketch to run a custom-formatted program from a sd card. I am working on creating, changing and reading variables but when I created the creating function, it printed weird numbers to the sd card. It printed 989711097110974449501310 for some reason. Here is the function:

void mkVar(String varn, String val) {
  varFile.seek(varFile.size());
  varFile.print(varn);
  varFile.print(",");
  varFile.println(val);
  Serial.print("p"); // Debugging purposes
}

The input was banana,12

2

Does your object allow for "write" rather than "print?" For example:

varFile.write(varn); // testing ".write"
3

@xfpd the write() function does not support Strings

4

I just saw this... a "decimal to ASCII converter" (if you separate the "letters" correctly) showed "ba...12"

CoderStool.com

Here it is:

98 97 110 97 110 97 44 49 50 13 10 
banana,12<CR><LF>

So... you need a way to "write" your String.

5

Thanks, my read function does say 12 when inputting banana. I still need to fix my changing value function

void setVar(String varn, String val) {
  varFile.seek(0);
  String d = "";
  while (varFile.available()) {
    d += varFile.read();
  }
  Serial.print("(" + d + ")");
  varFile.close();
  SD.remove("/sys/ram.txt");
  varFile = SD.open("/sys/ram.txt", FILE_WRITE);
  d.replace(varn + "," + getVar(varn), varn + "," + val);
  varFile.println(d);
  varFile.close();
}

When running the read function before changing, it is 12 but after changing it is blank

6

Try the dump in hex so you do not need to deal with 3-digit decimal:

varFile.print(varn, HEX);
7

Can you show another output showing this?

8

12<(989711097110974449501310)><
the stuff inside >< is the getVar data. the stuff inside the () is the what the sd card's contents are

9

That is still "banana,12"

10

after the brackets, it runs the setVar() function to change the value. that function does not work so the next reading (the >< after the brackets) are blank

11

Could this be because varFile.read() returns an int, so d += varFile.read(); will append the hexadecimal decimal representation to the string d? Try doing d += char(varFile.read()); instead to see if that fixes it.

12

It will append the number in "normal" decimal notation, hence 989711097110974449501310.

The reason read returns a signed int instead of a char (or uint8_t) is for when there is nothing available: it returns -1. So the loop can more obviously express this behavior like

int c;
while ((c = varFile.read()) >= 0) {
  d += (char) c;
}

(although that does leave the variable c in scope after the loop)

13

Calling read() until it returns -1 is my preferred method too. I've long thought that calling available() before read() is redundant since read() already tells you if anything was available.

14

I used char(varFile.read()); and it read it normal (it said banana,12 instead of 989711097110974449501310) thanks. The setVar() function still doesn't work sadly. I'll keep you updated

15

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