Default SPI frequency of 40MHz too high?

Admittedly, I haven't done the research on this, but for many microcontrollers, 40MHz on the SPI exceeds the limits. Perhaps a default value of something lower that is more clearly configurable, or perhaps the accompanying example application can pass in a lower default value that will be more compatible across platforms.

* @param freq Clock speed of the SPI bus (defaults to 40MHz)
*/

SPIFBlockDevice(PinName mosi, PinName miso, PinName sclk, PinName csel, int freq=40000000);

Start with the SPIFBlockDevice constructor declaration and the accompanying example application mentioned in the issue. Check the supported SPI frequency limits for the target platforms and determine whether the default belongs in the driver or the example; done requires an agreed, more compatible default or an explicitly configurable example value.

Written by the indexing model from the issue text.