Re: LIRC on Raspberry Pi 4B

Hi Sean,

Thanks for your hints so far!

Am Freitag, den 24.09.2021, 15:00 +0100 schrieb Sean Young:
> Hi Torsten,
> 
> On Tue, Sep 21, 2021 at 11:51:01PM +0200, Torsten Mohr wrote:
> > Hello,
> > 
> > I try to set up LIRC on a Raspberry Pi OS but doin't even have a
> > /dev/lirc0.
> > 
> > I downloaded the Raspberry Pi OS last week, the kernel version is
> > 5.10.60-v7l+.
> 
> Did you compile the kernel yourself?
No, I installed NOOBS-lite_v3_7 and then installed a standard Raspberry
Pi OS from that one.  From the subdirectories in /lib/modules and from
"uname -a" it is "5.10.60-v7l+".


> > I located the IR related kernel modules in this directory:
> > 
> > /lib/modules/5.10.60-v7l+/kernel/drivers/media/rc
> > In there are gpio-ir-recv.ko and gpio-ir-tx.ko (which I don't
> > need).
> > Also, there is no "gpio-ir.ko", but some more "ir-*.ko".
> > 
> > When I do "modprobe gpio-ir-recv" I see no fails in "journalctl
> > -f".
> > 
> > But also when "ls -l /dev | grep lirc" shows no output at all.
> > 
> > "lsmod | grep gpio" shows:
> > gpio_ir_recv    16384 0
> > 
> > To my understanding, the gpio-ir-recv is sufficient to provide a
> > "/dev/lirc0", is that correct?
> 
> No, gpio-ir-recv needs devicetree to tell it where the the IR
> receiver
> lives, that's how arm hardware discovery works. You'll need to either
> enable the correct overlay or edit the devicetree file and compile a
> new
> kernel.
Thanks for that hint.  I was unsure if this is necessary.  In a Howto I
found it said I need to "mount -o remount,rw /boot", but I skipped that
and my editing in /boot/config.txt were persistent, so I guess that is
fine?
The only thing I edited there is add a line at the end saying:
dtoverlay gpio-ir-recv

Here I noticed my first mistake, it should be dtoverlay=...
And after some googling I noticed my second mistake, though there is a
file gpio-ir-recv.ko, the dtoverlay line should read:
dtoverlay=gpio-ir

Then in /proc/device-tree I see:
ir-receiver@12

And also, there is a /dev/lirc0 now !!

I have then learned my new remote control with irreceive, rebooted
and see that it is used when typing "/etc/init.d/lircd status".

Thanks  !!!


Best regards
Torsten

> > Also when I additionally do "modprobe ir-rc5-decoder" then there is
> > no
> > /dev/lirc*.
> > 
> > I tried numerous Howtos I found, most refer to "gpio-ir", not
> > "gpio-ir-
> > recv", I did not yet find out if this is the same.
> > 
> > Also, on the Raspi many Howtos describe changing /boot/config.txt
> > to
> > mention the kernel module in there.  I tried that, it makes no
> > difference.
> 
> What changes did you make to /boot/config and what is the output of
> ls /proc/device-tree/
> ?

> As a receiver I use the "RemotePi Board + 2015" which has the GPIO
> > compatible IR receiver on GPIO18
> > 
> > To my understanding this fail seems to be very basic and already in
> > the
> > lowest layers (no userspace involved yet) and the points that could
> > influence it are:
> > - boot/config.txt
> > - the used kernel module
> > - the GPIO pin
> > 
> > To my understanding, the configuration in /etc/lirc is not yet
> > important, am I correct?
> > 
> > Has anybody got a hint on what to try to make LIRC work on the
> > Raspberry Pi 4B?
> 
> I don't think it should be any different from any other Raspberry Pi.
> 
> Thanks,
> Sean