Adam,
Can you call a subroutine which then makes a system call?
Sincerely,
David Smead
www.amplepower.com
www.amplepower.net
On Wed, 14 Nov 2007, Adam Dunkels wrote:
Grant Edwards wrote:
On 2007-11-14, Grant Edwards <[email protected]> wrote:
Is anybody aware of a lightweight coroutine implementation for
mspgcc? The yield operation would need to be implemented
without disabling interrupts...
Protothreads looks promising:
http://www.sics.se/~adam/pt/
Yes, protothreads do not require any interrupt-disabling code (or any
other low-level code for that matter - no assembler, no stack
manipulation, etc - protothreads are pure C). The memory overhead is
very low: only two bytes per protothread. Beware, however, that because
protothreads are stackless, local variables are not stored across a
blocking wait. Either use static local variables or pass around a state
struct like event-driven programming.
The overhead or protothreads compared to an explicit switch()-based
state machine is a few cycles so protothreads can even be used in
time-critical code such as interrupts [1]. We're using them in Contiki
[2] for a bunch of different purposes ranging from low-level radio
framing protocol parsers (inside an interrupt handler) to the high-level
process structure of Contiki.
/adam
[1] Adam Dunkels, Oliver Schmidt, Thiemo Voigt, and Muneeb Ali.
Protothreads: Simplifying event-driven programming of memory-constrained
embedded systems. In Proceedings of the Fourth ACM Conference on
Embedded Networked Sensor Systems (SenSys 2006), Boulder, Colorado, USA,
November 2006.
http://www.sics.se/~adam/dunkels06protothreads.pdf
http://www.sics.se/~adam/dunkels06protothreads.ppt
[2] http://www.sics.se/contiki/
--
Adam Dunkels <[email protected]>
http://www.sics.se/~adam/
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