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Diffstat (limited to 'docs/reference')
| -rw-r--r-- | docs/reference/isr_rules.rst | 29 |
1 files changed, 29 insertions, 0 deletions
diff --git a/docs/reference/isr_rules.rst b/docs/reference/isr_rules.rst index 2db261c09..dfdee048c 100644 --- a/docs/reference/isr_rules.rst +++ b/docs/reference/isr_rules.rst @@ -124,6 +124,32 @@ A means of creating an object without employing a class or globals is as follows 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). +An instance of object creation occurs when a reference to a bound method is +created. This means that an ISR cannot pass a bound method to a function. One +solution is to create a reference to the bound method in the class constructor +and to pass that reference in the ISR. For example: + +.. code:: python + + class Foo(): + def __init__(self): + self.bar_ref = self.bar # Allocation occurs here + self.x = 0.1 + tim = pyb.Timer(4) + tim.init(freq=2) + tim.callback(self.cb) + + def bar(self, _): + self.x *= 1.2 + print(self.x) + + def cb(self, t): + # Passing self.bar would cause allocation. + micropython.schedule(self.bar_ref, 0) + +Other techniques are to define and instantiate the method in the constructor +or to pass :meth:`Foo.bar` with the argument *self*. + Use of Python objects ~~~~~~~~~~~~~~~~~~~~~ @@ -179,6 +205,9 @@ interrupt occurs while the previous callback is executing, a further instance of for execution; this will run after the current instance has completed. A sustained high interrupt repetition rate therefore carries a risk of unconstrained queue growth and eventual failure with a ``RuntimeError``. +If the callback to be passed to `schedule()` is a bound method, consider the +note in "Creation of Python objects". + Exceptions ---------- |