[mythtv-users] Re: MyIRBlaster - Myth Issues Only??
dwilga at MtHolyoke.edu
Thu Oct 27 11:41:23 EDT 2005
I have also experienced problems using LIRC to send IR signals
through the serial port. I believe the reason is LIRC's reliance on
the (low priority) RTC interrupt for timing. LIRC toggles a single
serial port control line up to 56,000 times per second, to directly
turn an LED on/off. If another thread takes control away from LIRC
for too long, a pulse gets stretched and the IR device becomes
However, this problem shouldn't affect devices like MyBlaster,
because its software uses standard serial I/O to send information to
the device. A single IR code consists of just a few bytes of data
sent using a slow (compared to LIRC) baud rate of 19,200 bps. The
MyBlaster then translates these few bytes into the many IR pulses
necessary to control the device.
I'm really surprised, and somewhat disappointed, to hear that even
MyBlasters have trouble. I was actually considering buying a
MyBlaster or constructing something similar on my own using a
Maybe I'll set up a test to just send serial bytes in a predictable
order and see if they get garbled or missed over time while Myth is
My setup incudes a 3.0 GHz P4 running on an ASUS motherboard that use
the ATI chipset. So none of that matches the original poster.
I am also using a PVR-250 and a PVR-350. There's no secondary video
card; I'm using the onboard ATI video.
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?"
More information about the mythtv-users