Documentation updates.

Author: peterhinch

FASTPOLL.md

@@ -1,13 +1,14 @@
-# A modified version of uasyncio
+# An experimental modified version of uasyncio
 
 This document describes a "priority" version of uasyncio. Its purpose is to
 provide a simple priority mechanism to facilitate the design of applications
 with improved millisecond-level timing accuracy and reduced scheduling latency.
 
-I remain hopeful that uasyncio will mature natively to support fast I/O
-polling: if this occurs I plan to deprecate this solution. See
-[this thread](https://github.com/micropython/micropython/pull/3836#issuecomment-397317408)
-and [this one](https://github.com/micropython/micropython/issues/2664).
+I am hopeful that uasyncio will support fast I/O polling and have a
+[PR](https://github.com/micropython/micropython-lib/pull/287) in place to
+implement this. If this (or other solution) is implemented I will deprecate
+this module as the I/O mechanism is inherently more efficient with polling
+implemented in C.
 
 V0.3 Feb 2018. A single module designed to work with the official `uasyncio`
 library. This requires `uasyncio` V2.0 which requires firmware dated

README.md

@@ -21,8 +21,11 @@ This GitHub repository consists of the following parts:
  * [A modified uasyncio](./FASTPOLL.md) This incorporates a simple priority
  mechanism. With suitable application design this improves the rate at which
  devices can be polled and improves the accuracy of time delays. Also provides
- for low priority tasks which are only scheduled when normal tasks are paused.
- NOTE: this requires uasyncio V2.0.
+ for low priority tasks which are only scheduled when normal tasks are paused.  
+ NOTE1: this requires uasyncio V2.0.  
+ NOTE2: I have a PR in place which, if accepted, will largely supersede this
+ with a faster and more efficient way of handling fast I/O. This modified
+ version should be regarded as "experimental". It may stop being supported.
  * [Communication between devices](./syncom_as/README.md) Enables MicroPython
  boards to communicate without using a UART. Primarily intended to enable a
  a Pyboard-like device to achieve bidirectional communication with an ESP8266.

TUTORIAL.md

@@ -908,11 +908,9 @@ comes from the `Lock` class:
 If the `async with` has an `as variable` clause the variable receives the
 value returned by `__aenter__`.
 
-Note there is currently a bug in the implementation whereby if an explicit
-`return` is issued within an `async with` block, the `__aexit__` method
-is not called. The solution is to design the code so that in all cases it runs
-to completion. The error appears to be in [PEP492](https://www.python.org/dev/peps/pep-0492/).
-See [this issue](https://github.com/micropython/micropython/issues/3153).
+There was a bug in the implementation whereby if an explicit `return` was issued
+within an `async with` block, the `__aexit__` method was not called. This was
+fixed as of 27th June 2018 [ref](https://github.com/micropython/micropython/pull/3890).
 
 ###### [Contents](./TUTORIAL.md#contents)
 
@@ -1269,11 +1267,14 @@ All devices must provide an `ioctl` method which polls the hardware to
 determine its ready status. A typical example for a read/write driver is:
 
 ```python
+import io
 MP_STREAM_POLL_RD = const(1)
 MP_STREAM_POLL_WR = const(4)
 MP_STREAM_POLL = const(3)
 MP_STREAM_ERROR = const(-1)
 
+class MyIO(io.IOBase):
+    # Methods omitted
     def ioctl(self, req, arg):  # see ports/stm32/uart.c
         ret = MP_STREAM_ERROR
         if req == MP_STREAM_POLL: