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[on:]

Hi all,

I'm logging sensor data to my SD card with the SDfatLib. This works, but writing takes quite a long time and during this process i cannot log data. So i want to reduce writing time.

I have set SD speed to "Full". On my SD card the quickStart example (inlcuded in the lib) gives me 8.00 Mhz. I was wondering if get a newer and better card whether this would increase this speed, or is dependent on the SPI bus?

Thank you!

[Reply #1 on:]

this thread tells me it does

http://arduino.cc/forum/index.php/topic,109862.0.html

off to buy me a faster card then!

[Reply #2 on:]

dunno.
SPI is not the true SD interface, but just a fallback for microcontroller like arduino. i don't think you'll get better results with better SD card. (edit: ok i was wrong)
also the library is slow because of the FAT filesystem elaboration. you should write data in raw format, if you are looking for speed. there are many discussion about this.

[Reply #3 on:]

The SD card class/speed has little to do with write speed.  The speed class is based on very large sequential writes using the SD write multiple command with pre-erase and the 4-bit SDIO bus.

The Arduino uses the SD single block write command with the SPI bus.  Often very cheap class 2 cards have better write speed on Arduino than class 10 cards.

You need to benchmark the card to see what its performance will be on Arduino.  You can use the SdFat bench example.

SdFat is the base library for SD.h and is here http://code.google.com/p/sdfatlib/downloads/list.