Serial Peripheral Interface

[quote="monkey_biz" post=86152RT-Kernel is what helps define real time intervals[/quote]
It is what ensures that certain bits of code are executed at well-defined intervals.

MachineKit is a program that just defines the HAL configurations to connect I/O's from linuxCNC?

No, Machinekit is a "fork" of LinuxCNC, it is a separate version of LinuxCNC that does all the same things, but in some ways slightly differently.

and if G-code isn't real time how does it manage to have real time movement?

The G-code program is interpreted into a motion queue, and the queue is passed to real-time.

Quite often the entire G-code file has been interpreted and queued (behind the scenes) before the tool even touches the work.

monkey_biz wrote:

ok so the G-code file has only the binary information in it?

No, it's the text file that defines the tool path. (or actuator path for a robot).

If you are still at the point of not knowing what G-code is, it is perhaps a bit early to be concerned about SPI hardware drivers.