Cannot open file with underscores using the SD library

Question

So I'm trying to create a new file that has underscores in its name. However, when I try this, no file is created.

This works

String fileName = "NMEA.txt";
mySensorData = SD.open(fileName.c_str(), FILE_WRITE); 

This does not work

String fileName = "NMEA__23_33_3__16_7_29.txt";
mySensorData = SD.open(fileName.c_str(), FILE_WRITE); 

Does anyone know why?

Answer 1

[The SD library] uses short 8.3 names for files.

source

• jlcv: Do you have any tips on how I can organize my files then? As you can see in the above format, I have it as NMEA__hr_mn_ss__yr_mm_dd.txt.
• jlcv: I tried String fileName = "/23_33_3/16_7_29/NMEA.txt" to organize it by directory and it doesn't seem to create them.
• Majenko: Have you actually created those directories? It won't magically make them for you...