**This is an old revision of the document!**

See the following posts for now until information is moved here:

SPI Clock Control Registers: http://www.esp8266.com/viewtopic.php?f=13&t=2367

SPI Sending/Receiving Data: http://www.esp8266.com/viewtopic.php?f=13&t=2413

Alternative to limited SDK SPI Driver: https://github.com/MetalPhreak/ESP8266_SPI_Driver