[mythtv-users] lirc output reliability

[Dan Wilga]

At 10:08 AM -0500 10/19/05, Robert Denier wrote:
>For some reason my lirc output has been very unreliable lately.  I keep
>getting wrong channels, particularly sense I went to dish 301 receivers
>from the newer model version.

I have the same problem. I believe it has to do with the fact that 
lirc relies on the RTC timer. If something happens to interrupt it 
while it's pausing, the frequency of the output will be off and the 
receiver will balk. I think what makes the 301 more sensitive to this 
than other IR devices is the fact that it operates at a higher 
frequency (56000 Hz) than most.

I'm using an opto-coupler to interface my serial port to the Dish 301 
receivers, so I know it's not an LED-related problem. I have tried 
niceing the lirc process so it won't be as likely to get interrupted, 
but that doesn't seem to help.

My next step is to build a device that will send the IR pulses 
independently of the PC, but I don't know how long that will take. 
For now I just put up with the occasional missed program.

By the way, I analyzed the signal received by the Dish receiver with 
an oscilloscope and compared it to what was being generated by my 
device. After tweaking, I came to this lirc config, modified from the 
stock "3100" remote:

begin remote

   name 3100
   bits           16
   flags SPACE_ENC
   eps            30
   aeps          100
   header        550  5830
   one           550  1550
   zero          550  2570
   ptrail        550
   gap          5530
   min_repeat      8
   toggle_bit      0
   frequency    56000

-- 
Dan Wilga                                         dwilga at mtholyoke.edu
Web Administrator                             http://www.mtholyoke.edu
Mount Holyoke College                                Tel: 413-538-3027
South Hadley, MA  01075            "Who left the cake out in the rain?"