Re: TI-H: IR Link
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Your close. There several IR data transmission formats. And I think there
is more than these...There is an organization out there somewhere that sets
the standards.
IrDA/HP-SIR, has a pulse width requirement (and some other stuff), within
a time window.
500 kHz ASK, 500 kHz is a logic "0", absence of 500 kHz is a logic "1".
Used at baud rates of 9600, 19.2 and 38.4 kbps.
38 kHz ASK (TV remote mode), similar to above except modulation is done at
~38 kHz (40kHz). Used at 2400 kbps.
Direct Access Mode, a logic 1 is transmitted with no IR output, a logic 0
is transmitted with IR output. No modulation is done with the data.
Radio Shack has one that decodes data off a modulated carrier from ~1kHz -
100kHz.
At 10:48 PM 10/31/96 -0600, Joe Paul Schneider wrote:
>Ok... the way most IR transmissions work as far as I know is that IR
>light, which, yes, is around 900 nm (the wavelength of the light), comes
>out of an IR led (duh... I know this is boring, but hold on a sec) which
>is connected to something like a 555 that modulates it (some word like
>that) at a frequency of about 40KHz... this is a standard for most IR
>transmissions... this 40KHz stuff is then send through a second pass
>(which is why a 556 is more useful) through a timer and modulated again
>anywhere from 100 Hz to 1000 Hz... sometimes higher if you have a good
>detector... The detector finds the 40KHz light, sends the on and off of
>the light w/o the 40KHz to a tone decoder, which searches for tones in
>between 100 and 1000.... if it finds it, it's happy...
>
>Here's a diagram... (this probably won't help any... but here goes)
>
>+-------------------------------------------------------------+
>
> ---------------- ----------------
> | /\ /\ /\ /\ /| | /\ /\ /\ /\ /|
> | || || || || || | || || || || ||
> | || || || || || | || || || || ||
> | || || || || || | || || || || ||
>------ / \/ \/ \/ \/------------------- / \/ \/ \/ \/-----------
>
>the big on and offs are the 100-1000 Hz frequencies and the small ones
>inside are the 40KHz frequencies...
>
>+---------------------------------------------------------------+
>
>Also, I don't think the idea of sending only when one of the wires is high
>would work because if there was interference of anykind, the receiving
>side would immediately go low, screwing up the whole transmission....
>
>I think you'd need to use flip-flops or something to that effect so the
>circuit would remember the last thing sent to it, and leave all wires at
>the state they were at until told otherwise... this way transmission
>errors would not happen very often since the sending port doesn't change
>any of its wires until the receiving one does...
>
> -Joe
> joschnei@sendit.nodak.edu
>
>
>
>
>
>On Thu, 10 Mar 1994, Steve Wrobleski wrote:
>
>> ti-hardware@lists.ticalc.org wrote:
>> >
>> > >3) I don't know how well two separate wavelengths of light would work,
>> > >they might interfere with each other. I've tried to find out, but no one
>> > >seems to know and I haven't tried myself.
>> >
>> > The two wave lengths shouldn't interfere with each other. But tell me,
>> > where is says "transmitter", and tells you the wave length, where do you
>> > buy a 950MHz ir transmitter? Don't you have to build one? What do you
>> > have to do to oscilate the binary values. I'm assuming that it will work by
>> > sending out a constant signal at the specified w-l for 'on', and nothing
>> > for 'off', right?
>> >
>> > -C.J.-
>> >
>> > ********************************************************************
>> > Unsolicited commercial e-mail to the poster of this message
>> > will be proofread at $70/hr, minimum charge $150. Submission
>> > of such e-mail to this address will suffice as contractual assent
>> > to the said charging schedule.
>> > ********************************************************************
>> >
>> >
>> >
>>
>> Its not mhz, its nm. It is a different color of light. Some ic's send
>> off/detect different color light better because of the stuff that is
>> added too them. The 900 nm will pick up insignificant amounts of 950 nm
>> radiation and vice-versa
>>
>> --Steve
>>
>
>
>
>
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