Timeline for Breaking a switch case from an ISR
Current License: CC BY-SA 3.0
9 events
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| Apr 16, 2016 at 8:07 | vote | accept | makepeace | ||
| Apr 15, 2016 at 10:13 | comment | added | Edgar Bonet | @JRobert: I fully agree with you. I posted this because I think it's a fun hack worth sharing. I already stated in the answer I do not consider this a clean programming technique. I just expanded on that consideration, just in case it was not already extra clear. | |
| Apr 15, 2016 at 10:13 | history | edited | Edgar Bonet | CC BY-SA 3.0 |
Addendum about the clean solution: no busy waits.
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| Apr 14, 2016 at 23:53 | comment | added | JRobert | Longjmp restores the context as it was at the setjmp call. It may be; I just don't know. It sounds like you had similar concerns in your caveat to inspect the assembly code and to test carefully. It's quite possible it will work as expected/desired. On the other hand, allowing the ISR to return first gives me a lot more confidence in the outcome. | |
| Apr 14, 2016 at 18:41 | history | edited | Edgar Bonet | CC BY-SA 3.0 |
No need to sei(), as longjmp() restores SREG.
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| Apr 14, 2016 at 18:33 | comment | added | Edgar Bonet |
@JRobert: "longjmp() may return to the mainline but with the ISR's context" I don't understand what you mean by "ISR context". setjmp() and longjmp() save and restore quite a bit of context, including all the call-saved registers and the stack pointer.
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| Apr 14, 2016 at 17:39 | comment | added | JRobert | ... You'll probably want to abstract away as much of the case code as possible into small functions where the actual work and the flag-testing will be done. This way, both setjmp() and longjmp() will have (had) the same context. | |
| Apr 14, 2016 at 17:39 | comment | added | JRobert |
I think longjmp() may return to the mainline but with the ISR's context; I'd expect some surprising behavior. But if you call setjmp() prior to the switch statement (or higher, if appropriate), and the ISR sets a (volatile!) flag to indicate it has been called, then each case could do if( flag ) longjmp(); as frequently as it is appropriate to do without leaving some operation partially completed. ...
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| Apr 14, 2016 at 16:01 | history | answered | Edgar Bonet | CC BY-SA 3.0 |