Subject:
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Re: Need Masses of Technical Info
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Newsgroups:
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lugnet.robotics
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Date:
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Tue, 12 Jun 2001 11:55:55 GMT
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Original-From:
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Andy Gombos <gombos_2000@IHATESPAMyahoo.com>
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Viewed:
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1375 times
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Kekoa Proudfoot wrote:
> Sean Watson <SeanWatson@ec.rr.com> wrote:
> > communication FROM the RCX TO the IR Tower/PC (as opposed to the other way
> > around)
>
> RCX->PC is difficult because of the tower hardware. The tower shuts off a
> few seconds after it completes transmission to save power. Messages from
> the RCX that arrive during or after the shut off are truncated or not
> received. The tower works best in request/reply mode where the PC requests
> something and the RCX replies to it. In request/reply mode, a good
> practical cap on the max number of data bytes to transfer from RCX to PC in
> one go is 256 (does not include header, complements, or checksum). Larger
> sizes might work, but I know 256 works. When grabbing the ROM image, I
> distinctly remember having to reduce the size to avoid losing data to the
> tower shutting off. I ended up using the 256 size.
After you get some data, like 768 bytes or something, send another signal from the
PC. The RCX waits for this, and then sends another 768 bytes. This should keep
the tower on for the right amount of time. Also, be careful of sending too much
data, increasing the duty cycle, and burning out the IR LED's in the tower or
RCX. They can be replaced, but it is probably hard.
Andy
>
>
> > communication from RCX to RCX
>
> This is not a problem, but if you use the standard firmware you are limited
> to one byte transfers. If you roll your own code to do this you can do
> pretty arbitrary stuff modulo general reliability of IR communication,
> which can be flaky depending on your lighting environment, orientation of
> RCXs, etc. I think LegOS might include some useful general IR code, but I
> am not sure.
>
> > and how the H8 chip talks to the RAM included in the RCX (not the RAM in the
> > H8, but the 32K of external RAM, I was not able to figure this out from the
> > Hitachi manual)
>
> If I remember correctly one or more pins are hardwired to tell the H8 to
> expect a memory to be attached to it. I/O ports 1, 2, and 3, and parts of
> port 4 are therefore dedicated to accessing the external RAM. The RAM is
> memory mapped into the H8 address space. There should be a diagram in the
> H8 docs that shows the various memory maps. One of those is the right one.
> Since I don't have the docs in front of me I can't tell you which it is,
> but you should be able to figure it out.
>
> -Kekoa
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Message is in Reply To:
 | | Re: Need Masses of Technical Info
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| (...) RCX->PC is difficult because of the tower hardware. The tower shuts off a few seconds after it completes transmission to save power. Messages from the RCX that arrive during or after the shut off are truncated or not received. The tower works (...) (25 years ago, 12-Jun-01, to lugnet.robotics)
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