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Kenneth,
> anyone tried pbforth ?
I wrote it so I'm biased...
> im doing a comparison between the different possibilities here
> and looking at pbforth i was somewhat intrigued, until i discovered that
> you cannot multitask(more than 1 thread of execution). anyone here tried
> pbforth and can confirme that ?
I'll get to the ttasker in a minute, but pbForth is the only alternative
firmware with native support for SERVOS if you use the simple circuit
I developed here:
<http://www.hempeldesigngroup.com/lego/servos/index.html>
The newest version 2.1.3 has an undocumented (for now) hook into the 1msec timer
that allows you to implement a very crude multitasker. In fact, this model
is used frequently in very small automotive applications.
The idea is as follows:
1. At the 1msec tick, do all the regular RCX stuff and then call the
mutli-tasker hook IF WE HAVE NOT ALREADY CALLED THE HOOK. Just before
we call the hook, set a flag that indicates we are about to do so.
2. Within the hook, do all the stuff we need to. You can implement
cooperative multitasking by performing some tasks evey 2 or 4th
or 100th time through the loop.
3. If the 1msec tick is called again, the hook won;t be entered because
of the flag.
It's a bit complicated, and I really am planning to add atutorial on this
very soon.
Although multitasking is neat, most of our simple robotics apps don't
really need it. The problem with pre-emptive taskers is that you generally
need a separate stack for each task. The single stack cooperative tasker
I'm proposing is a bit easier to understand.
Ill post a note here when the new tutorial is available.
Cheers, Ralph
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Check out pbFORTH for LEGO Mindstorms at:
<http://www.hempeldesigngroup.com/lego/pbForth>
Buy "Extreme Mindstorms: an Advanced Guide to Lego Mindstorms"
<http://www.amazon.com/exec/obidos/ASIN/1893115844/hempeldesigngrou>
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Reply to: rhempel at bmts dot com
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Message has 1 Reply:
 | | Re: somewhat off topic, but...
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| Repost to proper newsgroup... ===...=== I'm NOT biased because I DIDN'T write the thing... Forth is a wonderful language that has a proven track record. I don't use it in my job simply because management has never heard about it. I don't mean to (...) (22 years ago, 17-May-02, to lugnet.robotics.rcx.pbforth)
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Message is in Reply To:
| | somewhat off topic, but...
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| anyone tried pbforth ? im doing a comparison between the different possibilities here and looking at pbforth i was somewhat intrigued, until i discovered that you cannot multitask(more than 1 thread of execution). anyone here tried pbforth and can (...) (22 years ago, 15-May-02, to lugnet.robotics.rcx.legos)
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