SoftSPI library

This allows one to emulate a SPI bus / line over GPIO lines

If one doesnt have a SPI controller on a given hardware platform (i.e SOC or uC) or if the existing SPI lines are fully used up, then one can use some spare GPIOs to emulate a SPI bus.

Look in the source code for details, its pretty simple

One requires to define few constants and functions to adapt this logic to work on ones given hardware platform.