SPI interface


When using either a regular SD or micro SD in a product application using the SPI interface to write data, we typically see a 3 us wait time when writing data. However sometimes we see 20 ms wait times and occasionally we see 120 ms wait times. And if the disk has a lot files, we can get back to back 120 ms wait times. As we are not using a PC for this application we do not have enough RAM to buffer these long wait times.

Any suggestions on dealing with this? Note that a class 2 card performs much better than a class 10 card when using the SPI interface(concerning wait times). Are there “premimum” cards available that have less wait times?




If you want I send all my source files to you about doing SPI-communcation with a micro-sd card, I implement  additional retry mechanisme and so on.

Also if you haven´t and goes design your schematic provide a additional power off/on fet for the micro-sd.

Somethings the Sandisk is hanging and only a power off/on give a solution to get back in communication with de micro-sd

micro-sd cards from Samsung or other manufactors does have such problems in SPI-mode.

Reg, pmoonen