All transactions for sending and receiving are most-significant-bit first and least-significant last.
For technical details of the underlying hardware refer to [metalphreak's ESP8266 HSPI articles](http://d.av.id.au/blog/tag/hspi/).
## A note on the SPI busses
!!! note
The ESP hardware provides two SPI busses, with IDs 0, and 1, which map to pins
generally labelled SPI and HSPI.
If you are using any kind of development board which provides flash, then bus
ID 0 (SPI) is almost certainly used for communicating with the flash chip.
You probably want to choose bus ID 1 (HSPI) for your communication, as you
will have uncontended use of it.
The ESP hardware provides two SPI busses, with IDs 0, and 1, which map to pins generally labelled SPI and HSPI. If you are using any kind of development board which provides flash, then bus ID 0 (SPI) is almost certainly used for communicating with the flash chip. You probably want to choose bus ID 1 (HSPI) for your communication, as you will have uncontended use of it.
## High Level Functions
The high level functions provide a send & receive API for half- and