Re-using IR Decoder Chip

[Just Another Joe]

I have an old VCR which doesn't work very well mechanically any more,
which I was thinking of gutting, and using as a case for the Ocelot and
some associated circuitry (e.g. roZetta). The VCR's power supply,
together with some 5V regulators, could be used to power the circuitry
(and perhaps the Ocelot as well, I haven't determined that yet). And,
the existing IR sensor on the front panel could be connected either to
the Ocelot or to the roZetta. Perhaps one might even make use of the
front panel LCD.

The Ocelot is, to me, excellent for IR output, but its IR input is too
general purpose. For my application, a dedicated decoder would be
better, and it doesn't matter what code set the decoder is for, as my
remote control can learn the codes if they are not already in its
database. So, it makes no difference whether the codes originally
represented, for example, Play, Pause, Stop, etc. All that matters is
that I can use the codes in macros on the remote control, and the Ocelot
can be programmed to act upon those codes.

Now to the meat of the question: could the IR decoder chip in the VCR
be used for this purpose, to provide some already-decoded information to
a serial port (or a pin) on roZetta? Given the make and model of the
VCR, is there a way I could find out what IR decoder chip it uses and
then find a spec. sheet on that chip? Is this a workable idea?

--
Just Another Joe Remove .windows to reply.
Why be politically correct, when you can be right?

[Dave Houston]

Just Another Joe <address@sig.end> wrote:

>I have an old VCR which doesn't work very well mechanically any more,
>which I was thinking of gutting, and using as a case for the Ocelot and
>some associated circuitry (e.g. roZetta). The VCR's power supply,
>together with some 5V regulators, could be used to power the circuitry
>(and perhaps the Ocelot as well, I haven't determined that yet). And,
>the existing IR sensor on the front panel could be connected either to
>the Ocelot or to the roZetta. Perhaps one might even make use of the
>front panel LCD.
>
>The Ocelot is, to me, excellent for IR output, but its IR input is too
>general purpose. For my application, a dedicated decoder would be
>better, and it doesn't matter what code set the decoder is for, as my
>remote control can learn the codes if they are not already in its
>database. So, it makes no difference whether the codes originally
>represented, for example, Play, Pause, Stop, etc. All that matters is
>that I can use the codes in macros on the remote control, and the Ocelot
>can be programmed to act upon those codes.
>
>Now to the meat of the question: could the IR decoder chip in the VCR
>be used for this purpose, to provide some already-decoded information to
>a serial port (or a pin) on roZetta? Given the make and model of the
>VCR, is there a way I could find out what IR decoder chip it uses and
>then find a spec. sheet on that chip? Is this a workable idea?

No!

http://davehouston.net
http://tech.groups.yahoo.com/group/roZetta/
roZetta-subscribe@yahoogroups.com

[Just Another Joe]

On Sun, 24 Dec 2006 00:55:43 GMT, nobody@whocares.com (Dave Houston)
wrote in message <458ed001.730066593@nntp.fuse.net>:

> Just Another Joe <address@sig.end> wrote:
>
> >Now to the meat of the question: could the IR decoder chip in the VCR
> >be used for this purpose, to provide some already-decoded information to
> >a serial port (or a pin) on roZetta? Given the make and model of the
> >VCR, is there a way I could find out what IR decoder chip it uses and
> >then find a spec. sheet on that chip? Is this a workable idea?
>
> No!

Okay then, how about a purchased IR decoder chip, for example for a NEC
protocol? They should be fairly cheap. That should ease the load on
the cpu.

--
Just Another Joe Remove .windows to reply.
Why be politically correct, when you can be right?

[AZ Woody]

Won't you need "the cpu" to translate what's decoded and convert it to
serial anyway?

Help me folks.. the was an old cartoonist who used to draw cartoons of
complex ways to do simple things?

Oh wait.. I got it I think.. "Rube Goldberg"?


Just Another Joe wrote:
> On Sun, 24 Dec 2006 00:55:43 GMT, nobody@whocares.com (Dave Houston)
> wrote in message <458ed001.730066593@nntp.fuse.net>:
>
>> Just Another Joe <address@sig.end> wrote:
>>
>>> Now to the meat of the question: could the IR decoder chip in the VCR
>>> be used for this purpose, to provide some already-decoded information to
>>> a serial port (or a pin) on roZetta? Given the make and model of the
>>> VCR, is there a way I could find out what IR decoder chip it uses and
>>> then find a spec. sheet on that chip? Is this a workable idea?
>> No!
>
> Okay then, how about a purchased IR decoder chip, for example for a NEC
> protocol? They should be fairly cheap. That should ease the load on
> the cpu.
>

[Dave Houston]

Just Another Joe <address@sig.end> wrote:

>Okay then, how about a purchased IR decoder chip, for example for a NEC
>protocol? They should be fairly cheap. That should ease the load on
>the cpu.

I'm not sure what it is you are trying to accomplish. Decoder chips for
specific protocols went out of style about 20 years ago. A NEC decoder is
only useful for the NEC protocol and any microprocessor can do the same job
as well as handle other protocols.

IR receivers like the [optional] TSOP1100 used in roZetta handle carriers
from 33-57kHz and output the demodulated data envelope. The most widely used
IR protocols are fairly easy to distinguish and decode - there's little
processing involved. And, you really do not need to decode - as long as you
can output a unique code that is consistent for the specific sequence of IR
(or RF bursts) you can use that to trigger consistent responses.

Less widely used IR and RF protocols (there are thousands) are not so easily
handled as far as decoding but nothing you propose changes that.

Maybe an example will help. The snake-oil purveyors (Pay no attention to
that fishy looking fellow behind the curtain.) pushing Z-Wave make much ado
about it using DES encryption. I don't give a fig about the protocol or
about how it might be encrypted. I can capture a transmission and play it
back and it will have the same effect every time regardless of the protocol
and regardless of any method of encryption. The encryption does nothing
other than prevent neighboring systems from controlling your system - it
doesn't take DES encryption to do accomplish that.

http://davehouston.net
http://tech.groups.yahoo.com/group/roZetta/
roZetta-subscribe@yahoogroups.com

[Just Another Joe]

On Sun, 24 Dec 2006 03:08:34 GMT, nobody@whocares.com (Dave Houston)
wrote in message <458de98b.736604421@nntp.fuse.net>:

> Just Another Joe <address@sig.end> wrote:
>
> >Okay then, how about a purchased IR decoder chip, for example for a NEC
> >protocol? They should be fairly cheap. That should ease the load on
> >the cpu.
>
> I'm not sure what it is you are trying to accomplish. Decoder chips for
> specific protocols went out of style about 20 years ago. A NEC decoder is
> only useful for the NEC protocol and any microprocessor can do the same job
> as well as handle other protocols.
>
> IR receivers like the [optional] TSOP1100 used in roZetta handle carriers
> from 33-57kHz and output the demodulated data envelope. The most widely used
> IR protocols are fairly easy to distinguish and decode - there's little
> processing involved. And, you really do not need to decode - as long as you
> can output a unique code that is consistent for the specific sequence of IR
> (or RF bursts) you can use that to trigger consistent responses.
>
> Less widely used IR and RF protocols (there are thousands) are not so easily
> handled as far as decoding but nothing you propose changes that.
>
> Maybe an example will help. The snake-oil purveyors (Pay no attention to
> that fishy looking fellow behind the curtain.) pushing Z-Wave make much ado
> about it using DES encryption. I don't give a fig about the protocol or
> about how it might be encrypted. I can capture a transmission and play it
> back and it will have the same effect every time regardless of the protocol
> and regardless of any method of encryption. The encryption does nothing
> other than prevent neighboring systems from controlling your system - it
> doesn't take DES encryption to do accomplish that.

Okay, perhaps I'm misunderstanding how roZetta will capture IR. I took
it that the cpu would 'watch' a particular pin for transitions from the
IR indicating ones and zeros until a byte was accumulated, rather like
capturing serial bits and bytes. The timing and decoding would need to
be adjusted for each IR frequency and protocol.

Now, I've seen IR decoder chips which do the capture, and simply present
a byte representing the code to a serial port. That is what I meant by
easing the load on the cpu. This would be rather like using a W800RF32
to decode RF and simply present bytes to a serial port. But, if it
doesn't provide any real advantage with the IR, that's okay. It was
only an idea.

--
Just Another Joe Remove .windows to reply.
Why be politically correct, when you can be right?

[Dave Houston]

Just Another Joe <address@sig.end> wrote:

>Okay, perhaps I'm misunderstanding how roZetta will capture IR. I took
>it that the cpu would 'watch' a particular pin for transitions from the
>IR indicating ones and zeros until a byte was accumulated, rather like
>capturing serial bits and bytes. The timing and decoding would need to
>be adjusted for each IR frequency and protocol.

roZetta will capture IR in the same manner as the ocelot captures IR except
the TSOP1100 handles a wider range of carriers (33-57kHz) than the TSOP1138
used in the Ocelot (38kHz).

When the Ocelot "learns" an IR code it merely stores an image of the data
envelope in memory. When it later receives a code it compares the received
data envelope with those it has stored. The elegance of the system is that
such brute force methods give results that seem quite a bit more
sophisticated than they really are.

roZetta will only handle the X-10 IR protocol plus the extensions that Laser
Systems developed a few years ago. roZetta does not attempt to decode other
IR protocols (although it will output hex codes for the NEC protocol since
it's the same as the X-10 RF protocol). And, the IR and RF receivers use the
same input pin so they are mutually exclusive.

>Now, I've seen IR decoder chips which do the capture, and simply present
>a byte representing the code to a serial port. That is what I meant by
>easing the load on the cpu. This would be rather like using a W800RF32
>to decode RF and simply present bytes to a serial port. But, if it
>doesn't provide any real advantage with the IR, that's okay. It was
>only an idea.

The device you mention copied what I did with the BX24-AHT except they did
not realize that I was doing some decoding internally and making some logic
decisions before outputting the hex codes. The hex code output is inadequate
to fully discriminate between various types of X-10 RF codes.

Now, I have tried repeatedly to shift these discussions to the roZetta Yahoo
group since it is rather specifically about roZetta. I will not respond
further here.

http://davehouston.net
http://tech.groups.yahoo.com/group/roZetta/
roZetta-subscribe@yahoogroups.com