Subject:
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RE: Another update for WIRRL
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Newsgroups:
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lugnet.robotics
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Date:
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Tue, 22 Oct 2002 21:01:11 GMT
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Original-From:
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Rob Limbaugh <RLIMBAUGH@GREENFIELDGROUPavoidspam.COM>
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Viewed:
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776 times
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Just in case people are a bit confused by the schematic, the circuit would be
needed for each device that will participate in an RF bridge.
I abandoned the idea of using two different frequencies because:
1) As soon as you attempt communication between more than two devices, one
device would have to be a proxy messenger.
2) Using two different RF frequencies doesn't solve the IR-reflection-feedback
problem that would exist.
A single frequency solves #1 (BTW, the current IR communication is single
frequency: 38kHz). Using logic between the IR side and the RF side solves
direction switching and #2 by disabling the appropriate data path.
One solution could involve using a programmable logic device with 4 I/0 lines
(at least two in and two out). If data comes in from the RFRX first, then
ignore any incoming data on IRRX until ~1.67us after incoming RFRX data ceases.
If data comes in from the IRRX first, then ignore any incoming data on RFRX
until ~1.67us after incoming IRRX data ceases. With the right PLD, the I/O line
used for IR-out could be pulsed at 38kHz without an external oscillator circuit.
Even in this case, the one RF frequency could be used.
Another option would be to modify the "Hardwired RCX" solution Peter Balch came
up with (http://www.abs-robotics.com/other/hardware.htm). There are arrows in
the diagram indicating data direction. What you could gain by using different
RF frequencies is the ability to do full-duplex communication (which may require
customized firmware and/or PC software to unlock that ability).
Perhaps I should add a "pros and cons" section to the page for the various
ideas... The two ideas listed above have several other design issues to
consider beyond what is mentioned here.
I don't know much about electronics, either. Part of the reason for pursuing
this endeavor is because I'm getting bored with "Connect red wire from J5 to
spring 34". So, like you, I would hope that if I'm making a wrong turn, someone
would point it out to me.
- Rob
-----Original Message-----
From: Bluey [mailto:Wolf_and_eagle@spamblock.yahoo.com]
Sent: Tuesday, October 22, 2002 11:24 AM
To: lego-robotics@crynwr.com
Subject: Re: Another update for WIRRL
Instead of worrying about the half duplex communication,
wouldn't it just be easier to have tranceiver at two different frequencies?
If I am missing something, go ahead and say so. I know very, very little
about electronics.
Timothy
In lugnet.robotics, "Rob Limbaugh" <RLimbaugh@greenfieldgroup.com> writes:
> I just noticed at least one glaring error with the new schematic...
>
> Say, for argument, an RCX sends "1001", which, in IR, would be "0110". =
> The IR detector of WIRRL would do nothing for the first bit ("0"), but =
> the next bit ("1") should be sent over the RFTX, and, according to the =
> current logic/schematic, it is. However, I never disabled the line =
> between the RFRX and the Oscillator, so the RFRX will receive the =
> transmission from the RFTX (because all are same frequency). This would =
> make IR =3D 1 and RF =3D 1. According to the truth tables, priority =
> will be given to RFRX data and the third bit of IR ("1") would never be =
> sent.
>
> Apparently, while creating the truth tables, I gave consideration to =
> this... I just never included it in the schematic.
>
> -----Original Message-----
> From: Rob Limbaugh=20
> Sent: Tuesday, October 22, 2002 2:45 AM
> To: lego-robotics@crynwr.com
> Subject: Another update for WIRRL
>
>
> To those interested,
>
> I've made a new schematic (WIRRL Rev. 2a) using a better TX/RX pair =
> (Linx LC
> Series) and I think I've found a possible better solution for handling =
> flow
> of data. This new diagram eliminates three transistors and replaces the
> 4001 Quad-NOR with a 74HC00A Quad-NAND.
>
> Out of nowhere, it dawned on me that I should use a truth table to =
> figure
> out how to move the data. I've included the truth table information and
> logic diagram at the bottom of the page.
>
> Same link as before: http://www.abs-robotics.com/projects/wirrl.htm
>
> Maybe I'll have time this weekend to actually build it...
>
> - Rob
>
> PS - Just as before, I don't claim this circuit works... I haven't built =
> it,
> so I don't know. I'm still learning.
>
>
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Message has 1 Reply:
 | | Re: Another update for WIRRL
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| What's a "proxy messenger"? Couldn't the reflection problem be solved by placing a barrier in between the emitter and receiver? Timothy (...) (22 years ago, 22-Oct-02, to lugnet.robotics)
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