[mythtvnz] Serial IR blaster on USB to serial cable

[Robin Gilks]

> On Sun, 2010-08-22 at 14:37 +1200, Robin Gilks wrote:
>> > Hi guys,
>> >
>> > I found a cheap serial IR blaster online the other day and bought it.
>> > After it arrived I realised that I don't have a serial port on my
>> > computer!  Just a parallel one - why you'd want a parallel over a
>> serial
>> > I don't know.  So I borrowed a USB to serial cable from a friend and
>> it
>> > is recognised by the system.  Problem is that when you install lirc
>> and
>> > you activate the blaster option it asks you for the serial port you
>> are
>> > using and the USB version is not an option.  Anyone know whether I can
>> > actually make it work using this cable and what config file I might
>> need
>> > to modify to get the correct port working?
>>
>> No - it won't work. It *MUST* be a real serial port since if you look at
>> the wiring it uses either the RTS or DTR output control lines and the
>> lirc
>> driver waggles them 40,000 times a seconds with great accuracy. You just
>> can't do that with a USB stack.
>
> FTDI FT232* USB Serial chip in bit-bang mode is more than capable of
> doing this. It would be an interesting project to make it work. libftdi
> may help you in this regard :)

Drivers... drivers drivers drivers...

There must be a 101 ways of interfacing an infrared LED to a PC whether
its a serial port, parallel port (only just fast enough!!), PCI bus (using
one of the select lines or mapped I/O) or lots of capable USB devices.

For external USB stuff I'd prefer an Atmel 8 bit AVR micro doing USB
decode in software and bit banging the output to the LED - could download
different modulation code sets on the fly then. Someone still has to write
an lirc kernel device driver for it though so I'd use either a real serial
port or a USB MCE remote that has 2 3.5mm jacks in the back for IR
blasters (I'm using the latter in 2 places!!).

-- 
Robin Gilks