[mythtv-users] USB -> serial ir blaster troubleshooting

[Brian Wood]

On Friday 06 February 2009 09:36:05 Travis Tabbal wrote:
> Given the price of that blaster, it's probably one of the simple ones that
> won't work with a USB to serial converter. USB just doesn't support the
> kind of direct timing required to make those work. It can be done with USB,
> but you need a smarter device on the end.
>

Right. the simple blasters do not use the serial port in its intended way. 
They do not use the data lines at all, but rather use the handshaking lines 
to drive the LED directly, so you need to pulse the control lines in the 
proper pattern to get it to work, something not possible with most USB-serial 
solutions.

The "smarter" devices (the MyBlaster is an example) actually use the port in 
the intended way, accepting data on the proper data lines and generating the 
timing internally, and should therefore work with any Linux-supported 
USB-serial converter.

This is also why you can get more IR power (and hence range) from the smarter 
devices. There is just not much energy available on the handshaking lines, so 
you can't get a lot of power from an LED driven by them. Smarter devices have 
their own power supply, and can thus generate much more IR energy.

The MyBlaster is no longer available new, though it might be found on FleaBay 
or the like.

I love my MyBlaster, no LIRC needed, and it can learn new codes if necessary, 
though it already knows most of the common ones. Controlling multiple devices 
is easy, just call another instance of the perl script with a different 
device code. A rare case of something that "Just Works". I have never had a 
channel change failure I could trace to the blaster device (some were actual 
satellite receiver failures).

-- 
beww
beww at beww.org