Subject:
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Re: Several hardware questions.. Laser link Hardware expansion n' more
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Newsgroups:
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lugnet.robotics
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Date:
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Fri, 5 Jul 2002 12:17:12 GMT
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Viewed:
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902 times
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I have chased this topic around quite a bit in the last couple of years and
built a few prototype devices to perform "I/O expansion".
My final conclusion, having gone to the trouble of building a device which
permits two of the RCX motor ports and three sensor inputs to switched to
one of three banks of ports (giving a total of six controllable motors and
nine input ports) is it isn't worth it. The cost of the electronic parts, I
used MOSFETs for the switching, comes close to that of an RCX. Most people,
were they to have that kind of money to spend on multiplexing one RCX to
more ports, would rather spend it on a second RCX!
The real downside of multiplexing input ports is you can't easily
accommodate rotation sensors. I found that to be the single most annoying
problem. As an example, if you are building a tracked platform with left and
right side rotation sensors, the easiest way to partition the task is to use
two RCXs communicating via their infrared ports set to low power. One RCX is
set up as being responsible for platform movement (controlling the main
drive motors and handling the rotation sensor inputs to close the tread
speed loops) while the other takes care of the higher level control and
navigation functions. This simplifies the communication tasks to motor
control commands being sent one way and motor status reponses being sent the
other. Low level bump sensor overrides then also route into the motor
control RCX. It often seems to me that six sensor ports and six motor ports
seems more than twice as capable as three and three.
JB
In lugnet.robotics, Mike Payson <mpayson@dawgdayz.com> writes:
> The Ferarri book talks about some ways to add input or output ports. The=20
> option that looks most promising to me is detailed at=20
> http://www.akasa.bc.ca/tfm/lego_ms2.html
>
> =46rom that site:
> "I'm very Pleased to announce that my latest project the '(MS)2 Expander'=
> will=20
> expand your RCX's ports with very little additional programming. Some of =
> the=20
> possibilities are as follows;
> =20
> 1. 6 Full featured output ports!
> (3 banks of 2 output ports with 2 usable at any one time with full=20
> "Brake"/"Float" & Direction abilities)
> =20
> 2. 3 + 1 Full featured output ports & 3 + 2 Full featured input ports!
> (3 banks of 1 output port + 1 RCX direct port & 3 banks of 1 input port =
> + 2=20
> RCX direct ports)
> =20
> 3. 6 + 1 Full featured input ports! (At the loss of 1 output port)
> (3 banks of 2 input ports with 2 usable at any one time + 1 RCX direct i=
> nput=20
> port)"
>
>
>
> On Monday 01 July 2002 01:51 pm, MiB wrote:
> > Hi - I posted a letter just before and I don't know If it went thru.
> >
> > I take it again there - Is there some hardware modifications to Mindsto= • rm
> > so it can have more IO ports - like more Motor control ports and more
> > sensor ports? - And a second thougt goes to the IR link if that can be
> > modified to a long range laser link - (In case some one got tired to th= • e
> > programming)
> >
> > Also if the IR transmitter could be replaced by the IRDA transmitter th= • at
> > is placed on most of the laptoy these days.. In fact I don't have a se= • rial
> > line anymore here just USB.
>
> --=20
> Mike Payson | DawgDayz Dog Walking & Pet Sitting
> (206) 280-7295 | www.dawgdayz.com | mpayson@dawgdayz.com
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