Am Montag, 13. Februar 2006 19:46 schrieb Marc Lavallée:
> I'm new to the 1-wire technology.
>
> I'd like to interface over 30 DS2408 on a 1-wire bus, using ordinary
> ethernet cables, arranged in a topology of 2 or 3 branches with 10 or 15
> daisy-chained devices.
>
Branches are a big problem for the onewire hardware. According to
Dallas'/Maxim's own investigations, it's best to avoid star-bus topologies at
all cost. You have three options:
1. Change the star-bus into a looped-bus topology: Use four wires per cable,
two for the forward-direction to the branch end, two for the reverse
direction back to the root and connect it there with the forward direction of
the next brach.
2. Use the DS2409 chip and switch branches.
3. Use several host adapters.
> The total length of the cables could be over 100
> meters.
>
Should be no problem.
> I need to monitor momentary push-buttons connected to the I/O pins
> of the 2408 and I need to know about the chronology of their status
> (pressed or released).
>
> It would work on Linux, and eventually on OSX. What
> are my options?
>
It's really hard to monitor keypresses that way with a non-realtime OS.
Networked peripherals makes things even worse.
You have to do it by hardware. The simplest idea is to use the edge detector
circuits built into the DS2408. That will give you a "button was pressed
since last check" signal for each button.
Kind regards
Jan
--
I'm not in favor of senseless Micro$oft bashing.
I'm in favor of bashing Micro$oft senseless.
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