Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail
From: Lasse Langwadt <llc@fonz.dk>
Newsgroups: sci.electronics.design
Subject: Re: Ir remotes
Date: Mon, 20 May 2024 11:50:22 +0200
Organization: A noiseless patient Spider
Lines: 28
Message-ID: <v2f6cv$3tvoi$1@dont-email.me>
References: <v2esfv$3s1ts$1@dont-email.me> <v2etb9$3s8ci$1@dont-email.me>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Injection-Date: Mon, 20 May 2024 11:50:23 +0200 (CEST)
Injection-Info: dont-email.me; posting-host="a75d9c77c2cedba5e73953b84cdb6c19";
	logging-data="4128530"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX19Lrlol0jYDVf8Jrd/Reeb5+Ga1q9Cy0ec="
User-Agent: Mozilla Thunderbird
Cancel-Lock: sha1:MSnYzj4SzHHHVyTM0cKHB38FGEs=
In-Reply-To: <v2etb9$3s8ci$1@dont-email.me>
Content-Language: en-US
Bytes: 2252

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