Subject:
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Re: IR transmission
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Thu, 8 Aug 1996 19:38:47 GMT
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Original-From:
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Jeff Keyzer <jkeyzer@calweb.com[AntiSpam]>
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Viewed:
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4159 times
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>
> Jeff,
> You are right. Several things could be wrong here. First of all the precision
> resistor is VERY VERY important. This controls the frequency of the carrier
> signal. The freq is approx 1/(RC) where R = R4 and C = C6 of the the Handyboard
> IR Tx circuit. So with handyboard values, 1/(3.83k * 0.0068u) = 38.4kHz If
> you chose say a 4K resistor, this would be, 1/(4k * 0.0068u) = 36.8kHz plus any
> discrepancy due to the resistors 5% precision. This is probably too far away
> from the 40kHz desired.
Well actually, even though it's not a precision resistor, when I
installed it, I grabbed a bunch of resistors and measured each one with my
DMM until I found one which was between the 3.74 and 3.83 values Fred
specified. To further test this, I did a poke(0x1000, 0x40) to turn on the
IR transmitting circuit, attached my infrared LED, and aimed it at the IR
receiver on the HB. I then did the while (1) {if (4 & peek(0x1000)) fd(0);
else bk(0);} statement also listed in the HB debugging instructions. This
verified that the IR signal is, in fact, within the range of the IR sensor,
because the motor 0 BK LED turns on constantly when the LED is aimed
anywhere near the sensor.
>
> Secondly, I wrote the REC receive in such a way that it would accept and decode
> 2 different types of code. But the transmit code will only send one type of
> code. What do I mean?? If the Rx program sees a $4703 for a code (BTW the $47
> part should remain the same for all buttons on that device, eg VCR) then the
> actual transmission could have been one 2 possibilities. It could either be
> $47B803FC or $4703. Notice that $B8 = !$47 and $FC = !$03. Thus to make life
> easier and the Rx program more broad, I allowed it to accept either version.
> The Tx program sends the longer one, however, because well... this is the
> version that my remote sent.
I'm guessing that this is the problem. Makes me wish I had more IR
controlled devices I could mess with, until I found one that used the right
protocol.
> Could I make another version of the Tx program to do the shorter code? Quite
> easily. When can I get to it? Well my monitor went on the fritz last night
> and isn't accepting my video signal anymore. And I am almost done with some
> routines (non IC) to do PIC16c84 programming. Once I get that done I could
> make another Tx routine.
That'd be nice! :-)
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Message is in Reply To:
 | | Re: IR transmission
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| Jeff, You are right. Several things could be wrong here. First of all the precision resistor is VERY VERY important. This controls the frequency of the carrier signal. The freq is approx 1/(RC) where R = R4 and C = C6 of the the Handyboard IR Tx (...) (30 years ago, 8-Aug-96, to lugnet.robotics.handyboard)
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