Hello - I have been using the DFPlayer Mini module for years with great results. It is my go-to MP3 player. I have been given a new project where I need to be able to determine the number of MP3 files in several different folders. Previously, all of my files were in folder 01 on the SD card and the code for reading the number of files in that directory is:

serout TxPin, T9600,[$7E,$FF,$06,$4E,$00,$00,$01,$FE, $AC, $EF]
pause 10
SERIN rxpin, T9600, 500, Done, X0,X1,X2,X3,X4,X5,X6,X7,X8,X9 'read in reply
NumFiles = X6 'X6 has # of files

This code works perfectly and always gives the correct number. Note, if I do not use the checksum, it does not give me the right answer. OK - now I have 3 folders on the SD card: 01, 11 & 99 with 01 having 7 files, 11 having 5 files and 99 having 8 files. I used those folder numbers since there were examples in the DFPlayer data sheet that used them and I wanted to try and duplicate what they presented. According to the data sheet, the command to query folder 11 ($0B) is:

serout TxPin, T9600,[$7E,$FF,$06,$4E,$00,$00,$0B,$FE, $A2, $EF]

That should have returned 5. When I run it, it returns 7 which is the number of files in 01. If I change the number of files in 01, the value returned for 11 is always the same as what is in 01. When I query the number of files in folder 99 ($63), again, I get the number of files in 01. Ideally, I would like to have folders 01, 02 & 03 and be able to determine how many files are in each. Has anyone had any success doing this? Thanks!