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Ralph, Thanks for reigning in the rabbit chase!
As the originator of this thread I'd like to respond to the 'why'...
I keep running out of ports on my creations. I see 5 or 6 as a practical limit. My criteria for a
solution:
1. Entirely compliant with RCX firmware.
2. Clean programmability. My initial idea: control is accomplished by setting the power level of a
port to select which device, and by setting the second port for actual device performance (on/off,
fwd/rev, pwr level). This means it would be usable by the RIS software.
3. Reasonable cost (In my mind this means < $50).
4. Leave at least 1 port for normal, direct RCX control.
The directions this thread has taken are not attaining this goal. Instead of blue-sky ideas about the
theoretical possibilities I'd like to see possibilities/critisisms towards an attainable project. Am I
way off base on the ability to create a simple circuit that measures various PWM to enable a set of
ports? If this is am expensive undertaking then say so now so more time isn't wasted on this topic.
If someone has a simpler idea for attainment of more than 3 outputs then I am all ears.
-Wes
Ralph Hempel wrote:
> Lou Sortman wrote:
>
> > Thanks for checking this out. This is important to know. I assume, then, that the duty cycles
> > are 1/8 through 8/8 as well as off, which would be 0/8. Can anybody verify this (with a scope or
> > something)? I have long wondered whether the duty cycles were linear or followed some nonlinear
> > curve.
>
> I have checked this out, and if you use the standard RCX firmware (or other firmware
> that uses the RCX ROM, then you get the waveforms you are talking about at 125Hz
> 1/(1ms x 8). You also get polarity information - oh no, I've said too much.
>
> > I thought that NQC used the same firmware as the RIS software, and, therefore drove the ports the
> > same way. I guess either the documentation is wrong, or the highest or lowest power level is
> > missing.
>
> Dave Baum, correct me if I am wrong, but I use the internal RCX ROM code to
> do the motor driving for pbFORTH, and I'm pretty sure NQC does the same thing.
>
> In other words, NQC and RIS use the SAME code to drive the ports.
>
> Seems to me that all of this talk about multi-device control assumes:
>
> 1. That you REALLY need to do this
> 2. That the RCX using standard firmware can process information for you
> 3. That you use non-LEGO software to do the work (legOS,NQC,pbFORTH)
> 4. That you want to spend a lot of time and money getting it to work
>
> With all of the talk about RS232 converters, and PWM decoders, why not buy a
> single board computer and do everything from your PC?
>
> I've been with the group for a couple of years now, and in my early emergence
> from the Dark Ages though it would be neat to make a single board computer
> for LEGO control. Then I thought about it a bit (I'm an embedded systems
> designer with 15 years exp) and decided it wasn't worth the effort, and then TLG
> came out with Mindstorms. I have always maintained that "neat to do" was fun
> until it became a mishmash of technology that was hard to get working. I had
> fun doing pbFORTH for the RCX because it did not cost me much except some time
> over the holidays. Now I can focus on BUILDING stuff, instead of fiddling and
> wishing for things to build.
>
> If you still want to do this, go ahead, we'll support you as much as possible.
>
> Cheers,
>
> Ralph Hempel - P.Eng
>
> --------------------------------------------------------
> Check out pbFORTH for LEGO Mindstorms at:
> <http://www.bmts.com/~rhempel/lego/pbFORTH/default.html>
> --------------------------------------------------------
> Reply to: rhempel at bmts dot com
> --------------------------------------------------------
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