SD card not being detected or accessible on Teensy 4.0

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For a project I would need to record I2S MEMS microphones data into a SD card to analyse it offline.
For now I encounter some issues with the SD card.

I'm using the T4 and an audio schield, just to do the tests I will then solder a SD port directly on the T4.
My SD cards are a Samsung EVO Plus U1 and a SanDisk Extreme PLUS U3. Both are 32GB SDHC.

I just ran exemple sketchs like the CardInfo with the SD.h library and the SdInfo with the SdFat library. I just set the chip select to 10.

With both libraries the Samsung Card is not detected and the SanDisk is detected but not usable. For example in the SD.h CardInfo example I get "Could not find FAT16/FAT32 partition.Make sure you've formatted the card".

Of course I formatted and refformated the card to a FAT32 partition.

My best guess for now is that these SD cards are not compatible but I find it strange therefore I would like to have confirmation before ordering a new one.


No, your SDcard should be fine fine.
Q: how did you solder " SD port directly on the T4"?
On the Audio card bottom silkscreen what is the printed letter for "Rev"?

Only the "Rev D" board works properly when directly pinned to the T_4.0.

Images and pin details are noted on this page:

Not noted in post #1 :: what version of TeensyDuino is installed? Not sure when any relevant changes may apply - but the current version is TD 1.51 with a beta 1 for TD 1.52 is posted on the forum.

This section at the start of setup() works here with a T_4.0 and REV D audio board.
>> CS is set to 10
>> The lines that modify SPI pins are left commented for this combination
const int chipSelect = 10;

void setup()
  //SPI.setMOSI(7);  // Audio shield has MOSI on pin 7
  //SPI.setSCK(14);  // Audio shield has SCK on pin 14

Output for my card shows FAT32::
Initializing SD card...Wiring is correct and a card is present.

Card type: SDHC

Volume type is FAT32

Volume size (Kbytes): 15537664
Volume size (Mbytes): 15173

Files found on the card (name, date and size in bytes): 
SYSTEM~1/     2020-02-23 11:28:20
  WPSETT~1.DAT  2020-02-23 11:28:20 12
  INDEXE~1      2020-02-23 11:28:20 76
20200318.CSV  2000-01-01 01:00:00 80892
DL200318.CSV  2000-01-01 01:00:00 210866
SDTEST4.WAV   2019-06-30 16:54:10 17173152
SDTEST1.WAV   2019-06-30 16:53:20 16787550
SDTEST2.WAV   2019-06-30 16:53:52 16425698
SDTEST3.WAV   2019-06-30 16:54:00 13617358

I have another card formatted ExFAT and it still can see the card - just not the filesystem type:
Initializing SD card...Wiring is correct and a card is present.

Card type: SDHC
Could not find FAT16/FAT32 partition.
Make sure you've formatted the card
Thanks for your replies.
I found the problem. I assumed that the two ground pins on the audio shield were connected together so I only connected one of them to the teensy.
My bug was fixed when I connected the second one.


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