Re: Re-using IR Decoder Chip

[nobody@xxxxxxxxxxxx (Dave Houston)]

Just Another Joe <address@xxxxxxx> 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/
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