FatFs printing random characters with snprintf

Asked May 04 '23 at 17:34

Active May 04 '23 at 17:43

Viewed 58 times

SD card output:

SD card output

I'm trying to write a string to an SD card using the FatFs library. I'm using the snprintf function to add a variable 'temp' to a string. When the string is written to the SD card there is also random characters there. I've tried using sprintf and also added a null terminator '\0' at the end of the string, but the random characters are always there.

int temp = 20;
char array[200];
snprintf(array, sizeof(array), "Hello there %d", temp);

edited May 04 '23 at 17:43

Barmar

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asked May 04 '23 at 17:34

Jeremy Prichard

5

But how are you writing to file? – orhtej2 May 04 '23 at 17:39
5

It looks like you're writing all 200 bytes, not just `strlen(array)`. – Barmar May 04 '23 at 17:44
I suspect that when you are trying to write to the file the code expects a null terminated string. Change `char array[200];` to `char array[200] = {0,};` to see if it solves your problem. – Jardel Lucca May 04 '23 at 17:44
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@JardelLucca `snprintf()` adds a null terminator. – Barmar May 04 '23 at 17:45
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`snprintf` returns the length of the string in `array`, so you can use that when you write to file. – Weather Vane May 04 '23 at 18:09

FatFs printing random characters with snprintf

0 Answers0