Mailing List Archive: MythTV: Mythtvnz

Serial IR blaster on USB to serial cable

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ross.jemima at gmail

Aug 21, 2010, 1:29 PM

Post #1 of 11 (1304 views)
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Serial IR blaster on USB to serial cable

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?

Cheers

Rossco

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g8ecj at gilks

Aug 21, 2010, 7:37 PM

Post #2 of 11 (1257 views)
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Re: Serial IR blaster on USB to serial cable [In reply to]

> 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.

I hope the serial blaster was less than $2 as thats how much they cost...

--
Robin Gilks

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stevehodge at gmail

Aug 21, 2010, 7:47 PM

Post #3 of 11 (1251 views)
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Re: Serial IR blaster on USB to serial cable [In reply to]

On Sun, Aug 22, 2010 at 8:29 AM, Ross and Jemima Knudsen <
ross.jemima [at] gmail> wrote:

> 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.

What motherboard have you got? There might be a real serial header on the
motherboard.

Cheers,
Steve

drtimlockyer at gmail

Aug 21, 2010, 7:51 PM

Post #4 of 11 (1262 views)
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Re: Serial IR blaster on USB to serial cable [In reply to]

It would be possible to create the 40,000 requirements using hardware with a
*555* Timer *IC and a and gate. Probably the IR repeater sold by Jaycar
would do the job.*

**

*Tim
*

On Sun, Aug 22, 2010 at 2:37 PM, Robin Gilks <g8ecj [at] 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.
>
> I hope the serial blaster was less than $2 as thats how much they cost...
>
> --
> Robin Gilks
>
>
>
> _______________________________________________
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> mythtvnz [at] lists
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>

g8ecj at gilks

Aug 22, 2010, 12:31 AM

Post #5 of 11 (1256 views)
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Re: Serial IR blaster on USB to serial cable [In reply to]

> It would be possible to create the 40,000 requirements using hardware with
> a
> *555* Timer *IC and a and gate. Probably the IR repeater sold by Jaycar
> would do the job.*

You possibly could do that but who is going to write the kernel driver for
it? That baseband 40KHz signal has to be modulated to generate the RC5 or
RC6 compliant signal - easier to either use a real serial port or a USB IR
blaster (as found in the Microsoft MCE remote) in the first place.

--
Robin Gilks

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ross.jemima at gmail

Aug 22, 2010, 2:49 AM

Post #6 of 11 (1255 views)
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Re: Serial IR blaster on USB to serial cable [In reply to]

Steve,

Thanks for the suggestion, I'll look into that.

Rossco

Robin:

Thanks for the information, you have answered my question.

On 22/08/2010 2:47 p.m., Steve Hodge wrote:
> On Sun, Aug 22, 2010 at 8:29 AM, Ross and Jemima Knudsen
> <ross.jemima [at] gmail <mailto:ross.jemima [at] gmail>> wrote:
>
> 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.
>
>
> What motherboard have you got? There might be a real serial header on
> the motherboard.
>
> Cheers,
> Steve
>
>
> _______________________________________________
> mythtvnz mailing list
> mythtvnz [at] lists
> http://lists.ourshack.com/mailman/listinfo/mythtvnz
> Archives http://www.gossamer-threads.com/lists/mythtv/mythtvnz/
>

dave2 at wetstring

Aug 26, 2010, 6:30 PM

Post #7 of 11 (1179 views)
Permalink

Re: Serial IR blaster on USB to serial cable [In reply to]

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 :)

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ross.jemima at gmail

Aug 27, 2010, 1:39 AM

Post #8 of 11 (1166 views)
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Re: Serial IR blaster on USB to serial cable [In reply to]

On 27/08/10 13:30, David Zanetti wrote:
> 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 :)
>

Hi David,

Thanks for the advice, it might serve someone with greater technical
expertise some benefit. I managed to find a serial port bracket for my
MB header and just fitted it. Now it comes to configuring it. The
default hardware.conf file generated seems to be fine, I just need to
adjust the remote config file to suit. The easiest way to do that would
be to record the keypresses wouldn't it?

Regards

Ross

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g8ecj at gilks

Aug 27, 2010, 4:33 AM

Post #9 of 11 (1164 views)
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Re: Serial IR blaster on USB to serial cable [In reply to]

> 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

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mythicalbeast at slingshot

Aug 27, 2010, 10:00 PM

Post #10 of 11 (1152 views)
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Re: Serial IR blaster on USB to serial cable [In reply to]

On Fri, 2010-08-27 at 23:33 +1200, Robin Gilks wrote:
> > 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!!).
>
But FTDI provide linux drivers (not kernel) & these devices are also in
lots of devices. I think some iMon use FTDI but then again that does not
recommend them does it !

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dave2 at wetstring

Aug 28, 2010, 12:21 AM

Post #11 of 11 (1149 views)
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Re: Serial IR blaster on USB to serial cable [In reply to]

On 27/08/2010 11:33 p.m., Robin Gilks wrote:

>> 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...

libftdi is open, and FTDI themselves provide a driver as well (same API
as their win32 one, the D2XX). And FTDI chips are well supported,
existing kernel code is just fine.

> 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!!).

Vastly overengineering it. Bitbang mode on the FTDI does buffering and
correct clocking out of the bits itself, as in, you can dump it a long
sequence in bulk and the chip will correctly clock it out for you.

http://www.huitsing.nl/irftdi/

Looks like someone already did it :) Appears to even manage to work for
reception as well.

--
David Zanetti <dave2 [at] wetstring>
http://hairy.geek.nz/

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