SD card test, strange results

[woodencase01]

I wanted to check what were the difference between SD card class within Teensy Audio application.

I'm using a Teensy 3.2
Working with PlatformIO on VS Code

Here is my methodology:

• Ran a clean format using SD Formatter
• Ran a CrystalDiskMark benchmark
• Ran the Teensy SD Card Test code
• Ran a custom code for reading WAV and RAW files

I have the following SD cards:
SanDisk 4GB SDHC Class 4
Patriot 16GB SDHC Class 10
Netac 128GB SDXC Class V30

I had to format the Netac to FAT32 to get it to work. I used this software.

For some reasons, the RAW files crashed the Teensy when using more than one sound.

Nevertheless, I managed to get some results I wanted to share with you.



For some reasons, the 4GB file have the best overall performance... But the audio performance is in par with the other synthetic benchmark.
Also, I think the CPU usage function is an approximation, but I only hear glitches using the 16GB card.

Also, considering the Class rating with Sequential Write, the Class 4 (8.2MB/s) performed better than the Class 10(6.5MB/s). Maybe there is a wrong class rating there, where the Patriot might be falsified?
The class V30 was closer to its specification (19.7MB/s).

 

[Deleted User]

On 3.2 the SD runs in SPI mode. The higher class ratings are more optimized for HC or XC mode, which uses more data lines.
Also, the Netac could be massively challenged by the FAT32 format, because the controllers on the larger cards are optimized for exFAT, this also includes wear leveling and block access.

 

[woodencase01]

Interesting, it makes a lot of sense.

Do you think there is a way the Audio library could work with the SD Fat beta, the one working with exFAT format?
I feel like there would be a lot of code to change, and I'm pretty sure it's beyond my knowledge.