Le 13 Février 2006 15:03, Jan Kandziora a écrit : > 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.
Maybe I would understand better with a schematic. > 2. Use the DS2409 chip and switch branches. Something like: http://www.hobby-boards.com/catalog/product_info.php?products_id=1511 ? > 3. Use several host adapters. Is OWFS able to manage several adapters? > 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. That might be enough. If it's not, then I can add a hardware latch in the circuit (a flip-flop?), because what I need to know is which key was pressed first. Paul Alfille wrote: > I was incorrect in my earlier note about the polling frequency. The DS2408 > has a latch, accessible through OWFS, that will save the button press. > This will greatly diminish the chance of missing a button press and reduce > the polling frequency. That seems to be the most elegant solution but I still don't understand how it works. At this point I should order a 1-Wire interface and a few 2408 in order to experiment. -- Marc ------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Do you grep through log files for problems? Stop! Download the new AJAX search engine that makes searching your log files as easy as surfing the web. DOWNLOAD SPLUNK! http://sel.as-us.falkag.net/sel?cmd=lnk&kid3432&bid#0486&dat1642 _______________________________________________ Owfs-developers mailing list Owfs-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/owfs-developers
