[mythtv-users] Re: MyIRBlaster - Myth Issues Only??
Dr. Doug L. Hoffman
hoffman at dlhoffman.com
Thu Oct 27 12:56:37 EDT 2005
I've been using a MyBlaster with my DishTV receiver for some time now
with no problems. The receiver sometimes gets hung up, but that happens
with the hand remote as well:-) I use a Pundit and dual PVR-250s.
On Thu, 2005-10-27 at 11:41 -0400, Dan Wilga wrote:
> 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
> confused.
>
> 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
> microcontroller.
>
> 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
> displaying video.
>
> 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.
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