Re: LIRC with custom receiver

[Alec L. <lea...@gm...>]

On 2014-05-21 04:10, Andrei Grigorev wrote:
>
> On Tue, May 20, 2014 at 9:19 AM, Alec Leamas <lea...@gm... 
> <mailto:lea...@gm...>> wrote:
>
>     On 2014-03-23 04:10, Andrei Grigorev wrote:
>
>         Hello,
>
>         I've built an IR receiver that is seen as serial port by
>         computer (/dev/tty<something> device in Linux). It sends
>         LIRC_MODE_MODE2 commands through the serial port. Is there an
>         easy way to make it work with lirc? Can you point me to
>         documentation on how to add support for new receiver devices?
>
>     Well, if you have a kernel driver sending data through a /dev/tty?
>     device you should really be able to use lirc 'as-is'. I haven't
>     done anything like this myself, but I think the first step should
>     be to use the mode2 tool which reads lirc data from a given device
>     and displays it. It has a manpage, but I'm afraid that's it.
>
>
> A little more details: it's a USB device it uses generic USB ACM 
> driver and seen in the system as /dev/ttyACM0.
> If I do something like
> cat /dev/ttyACM0 >~/data.bin
> then press some buttons on remote, then check the contents of the 
> data.bin file I see something like this:
>
> 0000000000: FF FF FF 00 5B 23 00 01 │ 47 11 00 00 75 02 00 01
> 0000000010: 47 06 00 00 74 02 00 01 │ F9 01 00 00 72 02 00 01
> 0000000020: 49 06 00 00 8D 02 00 01 │ E0 01 00 00 72 02 00 01
> 0000000030: FB 01 00 00 74 02 00 01 │ F9 01 00 00 8D 02 00 01
>
> Now, if I run mode2 I am getting this:
>
> # mode2 -d /dev/ttyACM0
> mode2: could not get hardware features
> mode2: this device driver does not support the LIRC ioctl interface
> mode2: major number of /dev/ttyACM0 is 166
> mode2: make sure /dev/ttyACM0 is a LIRC device and use a current 
> version of the driver
>
> How exactly am I supposed to run mode2 to have it read from device as 
> expected?
>

By not giving  any --driver option to mode2 you are using the lirc 
'default' userspace driver. This driver expects the device to be a 
regular kernel device implementing the standard lirc ioctl commands. 
What you see here is that your  device does not meet these expectations 
of the default driver. The exact answer how to handle this is beyond my 
lirc certification :) That said,  the way I see it there are two routes:

The first would be to implement the missing ioctl commands in your 
kernel driver. This way your device would be generally useful both for 
lirc and for other sw such as the kernel decoding.  The main definitions 
of these are in the file lirc.h which belongs to the kernel source (this 
is a bug[1]) and is bundled by the lirc distribution under include/. 
Unfortunately, there is not really any documentation I',m aware of on 
this; you would have to look into the kernel source to find examples.

The other route would be to write an lirc userspace driver which can 
cope with your non-standard device. Again, here is not much 
documentation and you would have to look into the lirc source to find 
usable examples.  Once this works you could use 'mode2 --device  
/dev/ttyACM0  --driver <your new driver>' .

In any case you probably want to rebuild lirc with debug enabled and 
turn on the debug printouts using --debug


Cheers!

--alec

[1] https://bugzilla.kernel.org/show_bug.cgi?id=75751