NetBurner Community Forum

I have a Nano-based project that reads and writes to a micro SD card on a custom board. This project was migrated from a MOD5234-based one on a different custom board that used an SD (not micro) card in SPI mode. The board for the Nano project was designed for 4-bit SD mode. My understanding is that the NNDK (2.6 is what I have) doesn't have a driver for the fast SD mode but it should still operate in SPI mode. I don't believe much (if any) of our file IO code has changed between the two projects.

The problem is that IO appears to be significantly slower on the Nano-based hardware. Calling f_format() on a 4GB Class 4 microSD card takes upwards of 2 minutes, where the same call takes 17 seconds for a 2GB SD card on the MOD5234 hardware. I realize that's a card half as big, but it still doesn't seem like it should take that long. I've also seen consistent writes of a ~40KB file take around 17 seconds on the Nano hardware and 4 seconds on the MOD5234.

Does anyone know why it's so slow, or can suggest what to look at?

Thank you

Have you tried a speed test on the netburner nano dev board? Would be good to rule out any issues on your custom board. Could be noise, coupling, etc.

Good suggestion. Turns out it works great on the NetBurner board - file write takes about 2 seconds and f_format() about 34, which makes sense given the 17 seconds for the 2GB SD mentioned earlier. Looks like it is the custom board. Thanks!