Subject:
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RE: brickos 090 problem no program download with CONF_LNP_FAST
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Newsgroups:
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lugnet.robotics.rcx.legos
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Date:
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Wed, 30 Apr 2008 11:57:02 GMT
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Reply-To:
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<DICKSWAN@SBCGLOBAL.NETavoidspam>
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Viewed:
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28619 times
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You should scan for some old posts by either John Barnes or Philo concerning
the different "IR transceiver" chips used between RCX 1.0 and 2.0 and
between serial vs USB towers. As I recall:
Serial tower can only transmit 38 KHz carrier. It's IR receiver is optimized
for 38 KHz.
USB tower can be set to either use 38 or 76 KHz transmission. Depending on
the application you use, the setting for this may not be exposed in an
interface. The IR receiver chip is optimized for 76 KHz carrier.
RCX 1.0 (i.e. the one with AC adaptor jack) uses same 38 KHz receiver as
serial tower. RCX 2.0 uses the same one as in the USB tower.
Due to harmonics, a IR receiver for one of the two carriers will generally
receive the other carrier frequency.
For best operation, you want to use a matched set where the transmitted
carrier frequency is the same as the IR receiver chip.
For completeness, I've tried to also use 9600 baud transmission. It simply
didn't work. The USB tower does not allow specification of this baud rate so
you have to use the serial tower. Unfortunately, it's fixed at a 38 KHz
carrier frequency which is not high enough for reliable transmission at 9600
as receiver chips need to get at least six carrier "cycles" per bit
transmitted.
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