SPI Clock Accuracy and microSD/microSDHC

Development Boards MicroMod
1

Does anyone know what clock accuracy is required for microSD/microSDHC cards via SPI?

I’d like to be able to write at 1-4 MHz with an Arduino Pro Mini 328 - 3.3V/8MHz. But, it’s clock isn’t very stable.

Has anyone tried this?

thanks,

glenn

2

The clock speed is irrelevant for SPI, provided it is below the maximum for the device.

3

Some devices also have a minimum :slight_smile:

However, the clock rate stability isn’t important. The only important factor is the cleanliness of the signals, which would matter with longer wire lengths and higher speeds. If you’re getting large reflections on your SPI bus, start looking for something else :smiley: