Mac OS X port and SoundCard Driver based on PortAudio Library

[Matthias R. <mri...@in...>]

Hi

I'm trying to get Lirc running on mac os x. On my machine there are no 
legacy ports like rs232 or parallel that I could use.
USB-2-Serial or USB-2-Parallel adapters wouldn't work as the home brew 
receiver only use interrupts on those ports.

I followed the idea that one could sample the IR signal with the sound 
card as Pavel Machek in hw_dsp.c but
used the normal TSOP 1738 instead of a simple diode and get the normal 
(long) range as any other receiver.

For the electronic stuff, I used 5V from a hard drive. To be able to 
connect the 5V TTL logic level to  the sound card
I used first 2 resistors (4,7 K and 1 K ) to reduce the  voltage to 
less than 1 volt and then a small capacitor ( I guess it was 100 pF)
to remove DC from it. I recorded the sound input using a sony remote 
and it clearly shows the bursts as rects. The level during one burst is 
decreasing
as one would expect as we try reading a constant voltage after one or 
more capacitors. The start pulse from the sony remote, 2400 uS, can 
clearly distiguished from the next pause.

I wrote an test app using the port audio library (available at least 
for linux, mac os 9, mac os x, several windows versions, ... ) to get 
the live data and detect pulse and pause values. this part works great. 
I used the heuristic that a difference of half the maximum level must 
be within 3 samples (44100 kHz).

Integration into LIRC is the stuff I'm not finished with. After 
changing some header files (there are no <linux/...> headers on my 
system.. :) and adding the gengetop package to get options parsing 
working, I was able to compile without drivers. I used hw_dsp as a 
starting point and added hw_audio to the makefile.am. The problematic 
part are the /dev/.. interface mechanism as mac os x doesn't allow 
user-land devfs and I didn't want to write a kernel extension. I 
decided to use a pseudo tty for the communication between the hw driver 
and lircd / irrecord. I disabled the /dev/lircd sockets, as this gives 
an error at run time and connect  to the lircd by the tcp/ip interface.

I got lircd running with a hand edited lirc conf file for my sony 
remote rmt-812. this one if for a sony dv camcorder  and uses 12, 15 
and 20 bit codes... so I used the raw mode. with irrecord I get only 
the  first pass working. This means the hw driver interface is not 
correct. I guess I will be able to get it working.

I just had a look into the lirc cvs and found the hw_udp driver. This 
would be another (easy debuggable) option for the soundcard driver.


resume: lirc compiles on mac os x, the sound card approach works fine 
here, the /dev/lircd is not working (without more effort), the hw 
driver needs a bit more work and the applications that uses lirc are 
missing. (I'm hardly using X11...)

Anybody interested in using/testing ?

Matthias Ringwald