At 05:40 PM 6/01/97 GMT, you wrote:
>> I have done bits and pieces... I've used a Sharp module connected to
>> a PIC 16C84.
>
>Which Sharp module did you use and how did you connect it to the PIC ?
>I've bought some samples of IS1U621, but havn't looked at them
>yet.

The module is GP1U52X(the only thing, IMHO, worth buying at Tandy/Radio
Shack). The circuit must have been the simplest PIC circuit I've ever
built. The module just connects to an input line with a pullup.
The Tx from the PC has a resistor in series. That leaves just the crystal
and the caps on either side. The PC and the VB program did the rest.

>
>Still, I feel that using receiver modules restricts your freedom
>when it comes to decoding IR remotes. You will probably only get
>signals modulated in the 36-42KHz range and miss those outside these
>frequencies (that will cover most remotes, but still...). Also,

There probably aren't many that have a different frequency. At least
the stuff I buy is one of the common brands and they all seem to operate
in that band.

>you might have problems with some of the very long
>headers as well as headerless protocols, but that might depend on
>the receiver. Given that you have enough RAM storage available,
>an idea would be to sample the raw IR signal, and demodulate it
>in software later. A sample rate of 100KHz would be enough for
>most IR remotes, provided the processor can trigger on the start
>of the IR sequence as it's being received. I assume sampling can be
>performed with the remote to be sampled very close to the IR receiver
>diode and with little other IR noise. That way it should be possible
>to get good samples with a crude transistor amp and without a proper
>filter.

Part of the problem might be to isolate the IR signal from other IR clutter
tough I have heard of people decoding it. The Sharp module seems to do a
pretty good job of detecting the signal. I suspect it uses one of those
single chip units where the whole thing is built into a TO-126 type of
package using an IR transparent plastic and has three pins - Vcc, Gnd and
output. The metal box does the all important job of shielding.

>I've never implemented raw IR capture on a PIC (and I don't intend to),
>but I've done it on PCs and Amigas and it does work. PIC capture of
>totally unknown remotes without IR receiver/demodulators can
>probably be done, but I've never seen the need in my applications.

Me neither.

>
>What unit are these values ? A good base value would be 25uS, since
>that the modulation carrier speed. According to
>http://falcon.arts.cornell.edu/~dnegro/IR/REMOTES/TABLE.HTML, the
>longest signal from a Sony Remote is the 2.2mS header pulse, which
>would correspond to 88 40KHz units. That should indicate that you may
>send all values below 128 uncompressed and values between 128 and 200
>divided by two, between 201 and 254 divided by 50 and 255 as any
>longer period. According to the table, no remote will send
>any signals (low or high) longer than (200 * 2 * 25)= 10000 uS,
>so longer values are only of value to detect retransmission speed and
>are (to my knowledge) not critical (a compression factor of 50 on
>retransmission delay would pose no problem with any remotes I know
>of).

As luck would have it, I had bought a cheap, old Phillips remote which was
to be the transmitter. It wasn't the usual RC5. It was a signal where the
time periods were really long - I don't remember what it was. Besides, I was
trying to squeeze the mark and space timings into the same byte. This gave me
a value from 0 to 15 to play around with. The compression wasn't uniform -
the level of loss of accuracy was not always in ranges of 4. Most of details
are a little hazy right now but I have the code somewhere... As the whole point
was to display a waveform on the screen, accuracy was not very important as
long the general pattern was discernable.

>Bob (tm)
Is that bob the process or Bob the name?
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