other IR detection?

Archiver

Hi group,

I'm a newbie...

I have read the articles "Control from the Couch" and "IR Detection &
40Hz" and am trying to get a grip on IR Detection.

The articles "seem" to imply that you need to have some idea of the
IR signal properties' to write the code to detect it correctly. For
example, the articles deal with the SONY IR command family and the
author 'knew' the pulse width was >7 wide and therefore wrote the
software code accordingly.....

What if my IR code family iS unknown? Is there any hope?

Peter

Archiver

Well, yes, you do need to have some idea of what your IR stream "looks
like" before you can demodulate it -- anything else is guessing (like a
blind date...). If you are using a different modulation scheme, you'll
need to find specs on it, or hook up a scope and take a look at what's
happening.

The SIRCS is well documented, easy to explain, and easy to decode with
the Stamp; hence the reason we use it in our projects and training.

-- Jon Williams
-- Parallax

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Original Message

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From: futurewalker [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=mkgXYduB_4L6T9HS_1Z8OJDR_YeiLqaZiSXV5kZAWMvn8fWzHql-HtGuvVqxhn8VztJK35gaoYMt-t13Kw]bs2@t...[/url
Sent: Friday, February 27, 2004 1:48 PM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] other IR detection?


Hi group,

I'm a newbie...

I have read the articles "Control from the Couch" and "IR Detection &
40Hz" and am trying to get a grip on IR Detection.

The articles "seem" to imply that you need to have some idea of the
IR signal properties' to write the code to detect it correctly. For
example, the articles deal with the SONY IR command family and the
author 'knew' the pulse width was >7 wide and therefore wrote the
software code accordingly.....

What if my IR code family iS unknown? Is there any hope?

Peter

Archiver

I once thought I was dead in the water where
this subject was concerned, but I've learned
since:

If you hook up a 40 KHz IR-Detector (3-pins,
+5, Gnd, and Signal), and you then hook up an
relatively in-expensive logic analyzer to it
(like the Ant-8, or the USBee), you can then
aim your remote at it and record the spacing
of the bits.

Having done that a bit, I then wrote a small
program on the BS2 that waits for the first
low on the signal line. It then uses
'PULSIN' to measure how long it is low, then
another 'PULSIN' to measure how long it is
high, and repeat for 16 bytes or so.
This only works for long-ish pulses,
like greater than 300 uSec. I havn't tried
this on any REALLY unknown protocols yet, but
it's on the list.

Note your accuracy will be reduced because of
the latency of the BS2's beginning to execute
the PULSIN instruction. A fast BS2 like the
SX may reduce this problem.


--- In basicstamps@yahoogroups.com, "futurewalker" <bs2@t...> wrote:
> Hi group,
>
> I'm a newbie...
>
> I have read the articles "Control from the Couch" and "IR Detection
&
> 40Hz" and am trying to get a grip on IR Detection.
>
> The articles "seem" to imply that you need to have some idea of the
> IR signal properties' to write the code to detect it correctly. For
> example, the articles deal with the SONY IR command family and the
> author 'knew' the pulse width was >7 wide and therefore wrote the
> software code accordingly.....
>
> What if my IR code family iS unknown? Is there any hope?
>
> Peter

Archiver

Hi Peter

I think there is a hope.



a while ago I hade the same problem with an Kenwood remote

I hook up a 3-pins IR-Detector (on Pin 10)

and used my BS2p to measure the pulses

I used a lot of PULSIN-command, followed by the DEBUG-command.

In the DEBUG window I could see that the first

Puls was about 5000 and then some pulses around 800 and others around 2000 (with
a BS2p)

a puls about 800 I thought as a LOW

a puls about 2000 I thought as a HIGH