[mythtv-users] Slightly OT - Help w/Homebrew IR Transceiver (LIRC PROBLEMS)

Scott Nicholson mythtv at scottnic.com
Fri Apr 16 10:06:49 EDT 2004


Okay... I've built the circuit. I didn't have a solderless breadboard (just
some perfboard) so I plunged in and soldered the thing together. I've gone
over the circuit several times and everything appears to be assembled
correctly.

But I'm having problems with LIRC. I first did "emerge lirc" (I'm on Gentoo)
and tried it out. When I couldn't get that working I downloaded the source
and used the "setup.sh" to configure it, then did "make" and "make install",
but I'm still getting the same problems.

I do /etc/init.d/lircd start, and lirc seems to load fine. (It's listed in
"ps -A", and /var/log/lircd lists "lircd(serial) ready").

I run "irrecord test.lirc" and get an error -- "could not open /dev/lirc".

If I run "irrecord -d /dev/lircd test.lirc" it runs okay, and /var/log/lircd
gets "accepted new client on /dev/lircd", "could not open /dev/lirc",
"default_init(): No such device" and "caught signal".

I assume the "could not open" and "no such device" mean something's not
working right, and sure enough, once I've pressed "RETURN" a couple of times
in irrecord I get "terminated" (in the irrecord messages) and lircd is no
longer running. (I have to do "/etc/init.d/lircd zap" and "/etc/init.d/lircd
start" to get it running again).

I've done some googling and searched this list and the lircd list, but
haven't been able to find anything that looks like it fits this situation.
Is this a hardware or a software problem? How can I test to find out? 

Any help will be greatly appreciated.


-----Original Message-----
From: mythtv-users-bounces at mythtv.org
[mailto:mythtv-users-bounces at mythtv.org] On Behalf Of Brian Rumple
Sent: Thursday, April 15, 2004 3:55 PM
To: Discussion about mythtv
Subject: RE: [mythtv-users] Slightly OT - Help w/Homebrew IR Transceiver

I'll start with the last one first, I only believe that excess voltage
would damage these parts but not polarity.  The basis for this is very
little knowledge and some experimenting when building mine.  I swapped
things around many times trying to debug my circuit.  I've forgotten 98%
of what I learnt in that one college hardware course.

It sounds like you have a good handle on building this thing.  I didn't
notice anything wrong while skimming your message.  I would suggest
building and testing on a breadboard before solder everything.

Last week I tried building a receiver with the 276-640.  I think that it
should work, but all my values from irrecord are the compliment of what
the real number should be (e.g. FFFF is coming out 0000).  There is a
sense option to lirc_serial module, but if a change it I get no response
from mode2. Do you mind sending me your experience after you build
yours?

The transmitter is real simple and works great.  Not very much range
though.



-----Original Message-----
From: mythtv-users-bounces at mythtv.org
[mailto:mythtv-users-bounces at mythtv.org] On Behalf Of Scott Nicholson
Sent: Thursday, April 15, 2004 12:18 PM
To: 'Discussion about mythtv'
Subject: [mythtv-users] Slightly OT - Help w/Homebrew IR Transceiver


I posted this to the LIRC list first, but haven't received a response.
This list is much more active. Hopefully there's someone here who can
answer this...

I'm going to make a transceiver based on the simple circuits provided on
the website, but it's been 10 years since I've done anything with
electronics, so I wanted to make sure I've got everything laid out
correctly...

Following the schematic at http://www.lirc.org/images/schematics.gif :

My IR Module is a Radio Shack 276-640 and its leads are labeled "Out",
"Gnd", and "VCC". These will correspond to the labels on the schematic
as
follows:

Out => data
Ground => (-)
VCC => (+)

Is that correct?

The long leg of the capacitor is (+) (and should connect to the VCC of
the IR Module and the Out of the Voltage Regulator), right? (The short
leg would then connect to ground)

The band on the Diode is (+) and should connect to the In of the Voltage
Regulator and to the resistor, right? (leaving the end without the band
to connect to pin 7 of the D-SUB)

Now, if I'm going to combine this with the simple transmitter circuit at
http://www.lirc.org/transmitters.html :

I connect pin 5 of the D-SUB to the non-banded side of the diode, the
banded side of the diode to the resistor, the other resistor lead to the
short leg of the IR LED, and the long leg of the LED to ground. Is this
right?

Please let me know if I've done anything wrong. (Will I damage anything
by connecting it incorrectly? I seem to recall that a capacitor can
explode if installed backwards. Can I fry an LED or the IR Module if I
do this wrong?)

Thanks,
Scott

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