If you have an extra pair in the wiring, you could use one pair in and one pair out so that the star is functionally a liner network bk
-----Original Message----- From: ekgnkb3d Sent: Saturday, September 17, 2011 7:05 PM To: owfs-developers@lists.sourceforge.net Subject: [Owfs-developers] increase OW reliability in bad topology Hi all, my problem is a little bit off-topic (because not specific to owfs), but maybe in this forum are the experienced 1-Wire net experts ;-) I want to replace in an existing building the 12 analog temperature sensors by 1-Wire DS18B20 temp sensors. The used cables are standard telephone twisted pair which are shielded together. They are in star-topology, so each of the 12 cable come from a different room (10m to 50m length each) to the central controller. So the complete net have a "weight" of approx 350m. The cables shall be reused, because it would be a hell a lot of effort to replace them too. As mentioned in http://www.maxim-ic.com/app-notes/index.mvp/id/148 Maxims application note 148 and http://docs.google.com/viewer?url=http%3A%2F%2Fwww.1wire.org%2FFiles%2FArticles%2F1-Wire-Design%2520Guide%2520v1.0.pdf 1-Wire.org Design Guides , the star is the most critical topology for 1-Wire nets. But what can I do, especially with OWFS, to increase the reliability of such a net? I've thought of the following already: - Using active pull-up bus masters, e.g. DS2482 with FET - If using 4 bus-masters, each one have to drive 3 sensors only and therefore reduce the weight to approx. 100m each. - Slowing down the net to 16kBit/s Standard Mode (how to do this on DS2482 with OWFS?) or even go slower down, to 8 or 4 kBit/s?? (The temperature is only needed each minute) - Problems usually look like the devices are lost, the search algorithm occasionally can't find some devices. Is there a way to configure OWFS to retry let's say 100 times until it really gives up? - Connecting each DS18B20 with 3 wires (+5V and 100nF Capacitor each) - Ensuring that the GND and OW-Data wire is a twisted pair of the cable - No termination resistor at the end of the cables any more constructive ideas? Thanks Achim -- View this message in context: http://old.nabble.com/increase-OW-reliability-in-bad-topology-tp32487173p32487173.html Sent from the OWFS - Dev mailing list archive at Nabble.com. ------------------------------------------------------------------------------ BlackBerry® DevCon Americas, Oct. 18-20, San Francisco, CA http://p.sf.net/sfu/rim-devcon-copy2 _______________________________________________ Owfs-developers mailing list Owfs-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/owfs-developers ------------------------------------------------------------------------------ BlackBerry® DevCon Americas, Oct. 18-20, San Francisco, CA http://p.sf.net/sfu/rim-devcon-copy2 _______________________________________________ Owfs-developers mailing list Owfs-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/owfs-developers
