Re: [PATCH 0/6] media: ite-cir driver cleanups

[Sean Young <sean@mess.org>]

Hi Hias,

On Fri, Feb 26, 2021 at 02:57:13PM +0100, Matthias Reichl wrote:
> On Wed, Feb 24, 2021 at 09:57:47AM +0000, Sean Young wrote:
> > That's a good point, that's probably the way to go. I'll have a look at
> > modifying my eeepc box.
> 
> On a second thought it's probably a bit more involved than just
> connecting an IR photo diode/transistor. CIRRX is a digital input
> and to get acceptable performance we'd also need an AGC circuit
> and a comparator / schmitt-trigger.

Yes, I had been thinking about building something like this.

> It might be easier to just feed a modulated digital signal into CIRRX,
> either from CIRTX or from a RPi running pwm-ir-tx.

That's a great idea, I hadn't thought of that. That's a lot easier!

> > Having said that, if all the hardware out there uses TSOP-type IR
> > receivers, I'm not sure how much use there is having this hooked up in
> > the driver; same for transmit.
> 
> If it's not too much hassle I'd vote for keeping the RX demodulation
> feature in the driver - it's an interesting feature and might come in
> handy at times.

It's kind of interesting, I agree. 

> For TX we need to keep carrier function as CIRTX always transmits
> modulated singals according to the IT8712 datasheet (unmodulated TX
> output would be quite odd, haven't seen that yet).

There are IR signals which are unmodulated. In IRP this would start
with {0k, and there are several of such protocols: Jerrold, Revox for
example:

http://www.hifi-remote.com/wiki/index.php/Revox

I never seen such hardware and I have no idea how well this works in
practise.


Sean