writeto_then_readfrom has been added to do a write -> no stop ->
repeated start -> read sequence. This is done to match the
capabilities of Blinka on Linux.
Code that uses stop=False will not work correctly on Blinka.
To fix, if stop=False then use writeto_then_readfrom otherwise use
writeto then readfrom_into.
First step in #2082
buffer from start, end and length. The old code miscomputed length
leading to writing and reading from memory past the end of the buffer.
Consolidating the code should make it easier to get right everywhere.
This was done to allow greatly granularity when deciding what functionality
is built into each board's build. For example, this way pulseio can be
omitted to allow for something else such as touchio.
Dan Halbert
Scott Shawcroft
Radomir Dopieralski
Jerry Needell
Scott Shawcroft