Documentation: added suggested introduction to interrupt handlers #1691
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Wow, thanks! I'll have to read through it properly but it looks good. "Why can't I allocate in an ISR" is a very common problem, and this should help (or at least provide a place to refer people to). Eventually it'll be nice to have "soft ISR" where response is less fast but you can allocate on the heap (as per a discussion elsewhere); and/or actually be able to allocate during a hardware ISR; and/or OS-level threads. But I still think this discussion about restrictions on ISRs is useful, especially for people new to embedded stuff, and especially because uPy uses a heap more than traditional C. |
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| red = Foo(pyb.Timer(4, freq=1), pyb.LED(1)) | ||
| greeen = Foo(pyb.Timer(2, freq=0.8), pyb.LED(2)) |
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I think there needs to be a paragraph here which describes the code above, what the interrupts are and what they call. Would also be good to explain that self.cb is a bound method which is how different state is passed around.
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After reading this interrupts sound pretty scary! I really think we need to implement "soft interrupts" which would alleviate almost all problems outlined in this document. But of course still allow hard interrupts when they are needed. I think the text needs a section "Tips and recommended practices" which is a sort of TL/DR section stating things like:
On a separate but related note, I will make a document describing things that do and don't allocate on the heap. That will help a lot to know what code you can write in a hard isr. |
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I've attempted to address these points. Is the concept of a "soft interrupt" detailed anywhere? It sounds intriguing. |
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Thank you! Merged in 521759e. |
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The new docs seem to lack links to this section. An entry under "The MicroPython language" and a link from tutorial section "5. The Switch, callbacks and interrupts" would help people find it. |
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The link under "The MP Language" is already there, just maybe it wasn't built correctly when you looked at it. And I just added a link from section 5 of the pyboard tutorial, in 1d191fd. Thanks for the tip! |
NOT TESTED! Just compiles Fixes micropython#1691
File added docs/reference/isr_rules.rst
Regular questions in the forum indicated the need for a basic introduction to the topic of writing interrupt callbacks, and this proposed addition stems from this discussion
http://forum.micropython.org/viewtopic.php?f=6&t=1156
The text can be viewed here http://hinch.me.uk/html/reference/isr_rules.html