Subject:
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Re: Anyone using Mac beige G3
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Newsgroups:
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lugnet.robotics.rcx.nqc
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Date:
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Thu, 1 Feb 2001 22:41:19 GMT
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Viewed:
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2030 times
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In lugnet.robotics.rcx.nqc, Gerhard Weiss writes:
> Kevin Hayes wrote:
> >
> > Hi all,
> >
> > I having trouble connecting a PowerMac G3 (beige model, 233MHz) to the
> > IR tower. I've tried NQC, MacNQC but keep getting "Error: no response
> > from IR tower". I've also tried ZTerm to see if I can get an echo back.
> >
> > The Green LED in the tower lights up when trying to connect so I know I
> > can transmit properly, but it seems I can't receive.
> >
> > I've heard reports of people using older Macs with NQC but nobody with a
> > beige G3. My QuickCam also no longer works in my beige G3 but did in
> > older Macs so I wonder if Apple changed the serial ports.
> >
> > So, is anyone using a beige G3 with Mindstorms? If so, what
> > cables/adapters are you using?
> >
> > Thanks,
> > Kevin
>
>
>
> I've had similar problems with a CyberMaster. It seems that
> CyberMaster Tower is powered by the serial interface (at least
> it is switched on by this power). On PC, the DTR line is switched
> high (12 V), and the CTS line is switched low (-12V). These lines
> do no signaling, but just supply power. On a Mac, you can
> have either DTR or CTS functionality, since there is only one
> handshake line out. Since the HandShakeLine Out seems to be used
> in DTR functionality (it goes to high, i.e. 4,5 V), I put the
> CTS line at the DB9 connector to ground. Now available voltage
> was only 4.5, but that seems to be enough. Unfortunatly,
> the output line (transmit signal from tower device) has now
> a swing of only 0 to 4.5 Volts, so it's no longer RS232
> compatible. It helped here to leave the Rx+ line of the
> Mac interface open. In this state it stabilizes itself to
> 2.2V- right in the middle of the available level - voila, here
> we go!
>
> Gerd.
One thing to keep in mind about Mac serial ports is that they are not RS-232,
rather they are RS-422. IIRC, RS-232 is a singled-ended voltage standard (ref to
ground only), where RS-422 is a differential standard. The 'common' method of
using one of the Rx pins for the serial out, is marginal at best.
Ray
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Message is in Reply To:
 | | Re: Anyone using Mac beige G3
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| (...) I've had similar problems with a CyberMaster. It seems that CyberMaster Tower is powered by the serial interface (at least it is switched on by this power). On PC, the DTR line is switched high (12 V), and the CTS line is switched low (-12V). (...) (24 years ago, 1-Feb-01, to lugnet.robotics.rcx.nqc)
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