Behaviour was changed from stack to queue in
8977c7eb58, and this updates variable names
to match. Also updates other references (docs, error messages).
This allows to efficiently send to an I2C slave data that is made up of
more than one buffer. Instead of needing to allocate temporary memory to
combine buffers together this new method allows to pass in a tuple or list
of buffers. The name is based on the POSIX function writev() which has
similar intentions and signature.
The reasons for taking this approach (compared to having an interface with
separate start/write/stop methods) are:
- It's a backwards compatible extension.
- It's convenient for the user.
- It's efficient because there is only one Python call, then the C code can
do everything in one go.
- It's efficient on the I2C bus because the implementation can do
everything in one go without pauses between blocks of bytes.
- It should be possible to implement this extension in all ports, for
hardware and software I2C.
Further discussion is found in issue #3482, PR #4020 and PR #4763.
It's more common to need non-blocking behaviour when reading from a UART,
rather than having a large timeout like 1000ms (the original behaviour).
With a large timeout it's 1) likely that the function will read forever if
characters keep trickling it; or 2) the function will unnecessarily wait
when characters come sporadically, eg at a REPL prompt.
This is only correct for the extmod/uos_dupterm.c implementation however,
as e.g cc3200 implementation does the mp_load_method() itself, and anyway
requires `read` instead of `readinto`.
The machine.sleep() function can be misleading because it clashes with
time.sleep() which has quite different semantics. So change it to
machine.lightsleep() which shows that it is closer in behaviour to
machine.deepsleep().
Also, add an optional argument to these two sleep functions to specify a
maximum time to sleep for. This is a common operation and underlying
hardware usually has a special way of performing this operation.
The existing machine.sleep() function will remain for backwards
compatibility purposes, and it can simply be an alias for
machine.lightsleep() without arguments. The behaviour will be the same.
Examples are added to the beginning of the module docs, similarly to docs
for many other modules.
Improvements to grammar, style, and clarity. Some paragraphs are updated
with better suggestions. A warning added of the effect incorrect usage of
the module may have. Describe the fact that offset range used in one
defined structure is limited.
Otherwise there is really nothing that can be done, it can't be unlocked by
the user because there is no way to allocate memory to execute the unlock.
See issue #4205 and #4209.
Damien George
Tom McDermott
Arsenijs
Jim Mussared
Nicko van Someren
Yonatan Goldschmidt
Matt Trentini
Paul Sokolovsky
Dave Hylands
Peter Hinch