Cannot open file with underscores using the SD library 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?
[The SD library] uses short 8.3 names for files.


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