Re: Ir remotes

On 5/20/2024 2:50 AM, Lasse Langwadt wrote:

On 5/20/24 09:15, Don Y wrote:

On 5/20/2024 12:01 AM, Don Y wrote:

My understanding is that Ir remotes modulate an Ir "carrier" signal
in a particular pattern to express a particular "code" corresponding to
the key pressed/held.
>
And, that different "chipsets" use different carriers and encodings.
>
Is there a front-end that is tuned to the particular carrier
in the receiver?  Or, is all of this done "digitally"?
>
I.e., with a fast-enough (Ir) photodetector, should I be able to
decode ANY signal from ANY "remote"?

>
And, before anyone mentions the obvious, I've already looked at lircd
which is the reason behind this post; why do they claim they can handle
ALMOST all remotes?  Is this a limitation of their hardware implementation?
Or, timing problems in the way they try to process the raw video signal?

 afaik almost all use a 30-50kHz carrier, nominally something like 38kHz,
I think the common IR receivers have build in bandpass filter, so it is just a matter of interpreting bits (there's a few common protocols)
 I know that B&O (used to?) be an exception with a 455kHz carrier, I'm guessing

Yikes!

because someone clever many decades ago thought to use an AM IF filter

If that is the case, then signaling an interrupt on each edge/cycle
would obviously kill a linux kernel (I've handled 140KHz interrupts
but 455KHz would really be an annoyance)  50KHz would be a piece of cake.
Thanks.  I should be able to verify this by looking to see what sort
of B&O devices are (or are NOT) supported.