pulsout

Archiver

OK so its

pulsout I/O pin, period

Ok so I'm understanding that if the I/O pin I'm using say p0 is low
when I call pulsout it will "pulse" to high for the period. But why
is it high for 2 times the period? That's what I'm reading in my A/D
project from parallax... Why doesn't it just let you specify exactly
how long to pulse???

Archiver

it does ask you how long to pulse. it is the period.
for example pulsout 2, 1 on a bs2 will be 2us
pulsout 2, 30 will be 60us
pulsout 2, 100 will be 200us
pulsout 2, 65535 will be 131070us or 131.07ms

ken smith


--- In basicstamps@yahoogroups.com, "packetdude2000"
<dark_archon1@j...> wrote:
> OK so its
>
> pulsout I/O pin, period
>
> Ok so I'm understanding that if the I/O pin I'm using say p0 is low
> when I call pulsout it will "pulse" to high for the period. But why
> is it high for 2 times the period? That's what I'm reading in my
A/D
> project from parallax... Why doesn't it just let you specify
exactly
> how long to pulse???

Archiver

doh remembering stuff now... thanks

Archiver

Maybe I forgot... but I was under the impression that the period for a
sine wave at least is the time between any two equivalent points. Then
1/t = f, and likewise 1/f = t. I don't get why you are multiplying it by
2. Pulsout does just go from the previous state then into an inverted one
for X time right? Then back to the original state?

Archiver

Does anyone has any experience in sending a pulse with PULSOUT through
a long wire let's say about 20m?

Thanks
Michael

Archiver

Haven't use pulseout, but have sent pulses many times.

If you want a real square pulse, then you will want to use a line driver
chip, a coaxial cable, and impedance match it at both ends.

Another method, you can send it through the wire pair (twisted is best), put
a resistance at the end across the wires, and use a comparitor or op amp
(configured as a differential receiver) to regenerate the shape.

But if you aren't picky and just need the pulse, it will propogate. Likely
there will be some leading edge and falling edge softening due to the
relatively high driving impedance of the stamp and the large amount of
capacitance on the cable.

How well it will work depends upon your exact application, but likely it can
be made to work, and relatively easily.

---

Original Message

---

From: magzi3 [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=mwU-Mw5GPyvYU2vXy3q5PYkG0Auf2uT7RESK3QG7rtb1AFVJ8BuBhB5ziBbpPEGnm0KNcaJ-By5_GZHOqYGH]magzi@p...[/url
Sent: Friday, February 13, 2004 3:49 AM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] PULSOUT


Does anyone has any experience in sending a pulse with PULSOUT through a
long wire let's say about 20m?

Thanks
Michael



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Archiver

For really long distances (4000 feet)
RS-485 works really well.

The problem with 'PULSOUT' is what do you
want to do at the far end? Detect that the
pulse occurred? (This is easy). Detect the
exact width of the pulse? (This is hard).

The width of the pulse is going to 'smear',
and the amplitude will drop,
because of the capacitance/resistance of
the cable. At 20 mA, the stamp has lots of
drive for its pins, so there's no reason
this can't work. You'll have to do some
proof-of-concept work to find the gotchas.
(in other words, do it and see what happens ;-) )

--- In basicstamps@yahoogroups.com, "magzi3" <magzi@p...> wrote:
> Does anyone has any experience in sending a pulse with PULSOUT
through
> a long wire let's say about 20m?
>
> Thanks
> Michael