summaryrefslogtreecommitdiffstatshomepage
diff options
context:
space:
mode:
authorPeter Hinch <peter@hinch.me.uk>2016-09-06 11:20:22 +0100
committerDamien George <damien.p.george@gmail.com>2016-09-07 17:12:42 +1000
commitdab0f316d26f4c77c94d9e51c35d5f63ed118d3c (patch)
tree81b76dbdda6a20aaab59f3b8d1b2ab6534dd8fb5
parent742d8bdbe46274401aa261881d14dee50a7618d5 (diff)
downloadmicropython-dab0f316d26f4c77c94d9e51c35d5f63ed118d3c.tar.gz
micropython-dab0f316d26f4c77c94d9e51c35d5f63ed118d3c.zip
docs/reference/isr_rules.rst: Two minor additions to docs for using ISR.
- Refers to the technique of instantiating an object for use in an ISR by specifying it as a default argument. - Footnote detailing the fact that interrupt handlers continue to be executed at the REPL.
-rw-r--r--docs/reference/isr_rules.rst30
1 files changed, 30 insertions, 0 deletions
diff --git a/docs/reference/isr_rules.rst b/docs/reference/isr_rules.rst
index b33e4dd6f2..23dcfd01f4 100644
--- a/docs/reference/isr_rules.rst
+++ b/docs/reference/isr_rules.rst
@@ -110,6 +110,19 @@ the flag. The memory allocation occurs in the main program code when the object
The MicroPython library I/O methods usually provide an option to use a pre-allocated buffer. For
example ``pyb.i2c.recv()`` can accept a mutable buffer as its first argument: this enables its use in an ISR.
+A means of creating an object without employing a class or globals is as follows:
+
+.. code:: python
+
+ def set_volume(t, buf=bytearray(3)):
+ buf[0] = 0xa5
+ buf[1] = t >> 4
+ buf[2] = 0x5a
+ return buf
+
+The compiler instantiates the default ``buf`` argument when the function is
+loaded for the first time (usually when the module it's in is imported).
+
Use of Python objects
~~~~~~~~~~~~~~~~~~~~~
@@ -300,3 +313,20 @@ that access to the critical variables is denied. A simple example of a mutex may
but only for the duration of eight machine instructions: the benefit of this approach is that other interrupts are
virtually unaffected.
+Interrupts and the REPL
+~~~~~~~~~~~~~~~~~~~~~~~
+
+Interrupt handlers, such as those associated with timers, can continue to run
+after a program terminates. This may produce unexpected results where you might
+have expected the object raising the callback to have gone out of scope. For
+example on the Pyboard:
+
+.. code:: python
+
+ def bar():
+ foo = pyb.Timer(2, freq=4, callback=lambda t: print('.', end=''))
+
+ bar()
+
+This continues to run until the timer is explicitly disabled or the board is
+reset with ``ctrl D``.