Hi Rob,
The DS2405 is really only good for outputs and reading inputs that are not
momentary. It should be fine for the high water alarm though.
As Jan pointed out, the DS2408 has a latch, and can be used for sensing
button presses. The DS2406 also has a latch and could be used the same way
(and will drop in in place of the DS2405s you already have). However, with
a DS2408 you only need to query one device for up to 8 (maybe 9?) buttons.
An ebay vendor, measureexplorer I think, has a tiny adapter board that is
suitable for mounting a DS2408 to so that you can connect it to a thru-hole
board like the space on the futurlec boards. It's only got 14 pads but pins
1 and 9 on the DS2408 are NC anyway.
Did you disable caching? It could be that the delay you are seeing is due
to the state being read from cache.
-Ben
On 4/5/07, Jan Kandziora <[EMAIL PROTECTED]> wrote:
Am Donnerstag, 5. April 2007 14:31 schrieb Rob Conway:
>
> NOW MY PROBLEM
> The digital input board uses DS2405 and I just read the sense parameter.
> It seems that regardless of how fast I scan these (2 sec or 20 sec) it
> takes 2 (sometimes 3) reads of the sense parameter before the state
> changes. Again if I physically turn off the input, the 1st read no
change
> the 2nd read it will show a change.
>
> I am now approaching 20 devices on the network and do not particulary
want
> to scan these Digital inputs twice as fast as nessecary. I am going to
use
> some inputs as "momentary buttons and a high level alarm" thus wanting
to
> read the status on every scan.
>
Aside from using a microcontroller as the host, the DS2405 is unsuitable
for
momentary buttons. To catch a single keypress, you have to scan right at
the
moment the key is pressed. With a multi-process OS like Linux, this is not
feasible. It's likely your application is currently suspended due to some
other process occupying the processor, so you lose the keypress.
Other problems like key chatter get in your way, too.
Use the DS2408 as a keyboard input. It has internal edge detector and
latches,
and a alarm function triggered as soon as an edge is detected. With this
chip, you eleminate the problems you have with the DS2405 and may use the
conditional search function (alarm directory) to check if any button was
pressed since last check.
Kind regards
Jan
--
A bureaucrat's idea of cleaning up his files
is to make a copy of everything before he destroys it.
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