Subject:
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Re: RCX Serial Hardware Hack
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Newsgroups:
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lugnet.robotics.rcx.legos
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Date:
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Thu, 29 May 2008 12:15:50 GMT
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Viewed:
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24054 times
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Dear Claude
In lugnet.robotics.rcx.legos, Claude Baumann wrote:
> In lugnet.robotics.rcx.legos, Bernhard Powolny wrote:
> > http://www-date.uni-paderborn.de/pub/people/dasas/Beh03.pdf
>
> I can't find it anymore neither.
A: Thank you for finding the PDF.
> > Then i have done as it is discriped in
> > http://www.convict.lu/Jeunes/RCXCam/RCXCam_Journal.htm
> > but i dont understand realy why we should do that?
> >
> > 1) To correctly use the H8 TX line with the CMUCam2 module, the driving RCX
> > software MUST shut down the 38kHz carrier
> >
> > like :
> >
> > void infrared_off() {
> > //! disable IR carrier frequency. // carrier_shutdown();
> > //extern inline void carrier_shutdown(void)
> > T1_CR =0;
> > T1_CSR =0;
> > }
>
> The carrier should be quiet in any case, because it disturbs the TX signal.
>
> > and
> > 2)set the port6<7> pin LOW. Now the upper PNP transistor isn't conducting
> > anymore.
> >
> > FOR WHAT reason...
>
> We tried this,but it didn't work. Why, because the transistor will drain some
> current, if the emitter has positive voltage and the base goes low. If the
> carrier is off, and by accident you set long range, then you have the chance to
> repeat what I did: kill a couple of infrared LEDs. Don't forget that they are
> driven at high current, but under the condition of a 50% duty cycle that is
> guaranteed by the carrier. If you shut down the timer, then the pin is high or
> low - the timer stops and you don't know the actual port6<7> state -
>
> If you have short range, the LEDs will rapidly heat also and only burn after a
> while. So, if your IR-TX doesn't work anymore... check you LEDs.
A: I will check ( measure the Voltage on the IF LEDS) should be approx. 9V
betweem LED and Transistor if everything is off.
> > But how managed the people from to http://www.convict.lu/Jeunes/RCXCam/RCXCam_Journal.htm
> > do it ????
>
> With the CMUCam2 everything works fine, even at 19600 as I said.
> > .
A: Now i had success . It works.
> >
> > more snap from the http://www.convict.lu/Jeunes/RCXCam/RCXCam_Journal.htm
> > It is important to add a 100k pull-up resistor to the TX line !!! Otherwise the
> > TX voltage will drop down to 0.45V it
>
> Pulling up the TX line IS necessary-at least with the CMUCam2, because the RX of
> this device is not pulled up.
I have allready done it.
>
> No idea, why it should not work. We have run our the CMUCam2 for hours at many
> occasions. We rebuilt the whole thing with another RCX, that we sent to Tufts
> Univ. They successfully played with the stuff.
A:Ok Now it works
best regards
Bernhard
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Message is in Reply To:
 | | Re: RCX Serial Hardware Hack
|
| (...) The carrier should be quiet in any case, because it disturbs the TX signal. (...) We tried this,but it didn't work. Why, because the transistor will drain some current, if the emitter has positive voltage and the base goes low. If the carrier (...) (16 years ago, 24-May-08, to lugnet.robotics.rcx.legos)
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