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Hi Attila,
I agree with both Markus and Mick: - you will most likely not need any additional diodes - watch your wiring However the below aspects I recommend you to evaluate, which are the reasons I am currently moving off 1-wire and will build an RS-485 based (home-brew modbus protocol-like) network: 1. The 1-wire bus is _not_ a computer network. If you ever want to transfer arbitrary data over the 1-wire bus in the future between your hosts it is not really supported. I found it hard-to-implement with onewire as it is designed to take standard 1-wire devices. As a 1-wire network grows this may become necessary for you (it became for me). The only solution I saw feasible is to build a special data endpoint device, which owlib could be modified to understand in a microcontroller but that is a lot of work (implement the 1-wire protocol, the search algorithm, get a unique bus address with an iserial, then indicate to owlib somehow that this is a special data endpoint device, etc.) maybe someone does it in the future and then we can have IP over 1-wire. An alternative would be to use ds2408's registers but these are simply not available (yeah, they are but around 20USD each) in my (and probably in your :) location. And this is just slow and cumbersome. 2. If you use owfs, then you do not always get proper feedback of what really happened on the bus as the OS file system may simply eat up the error - there may be workarounds with buffering adjustments and blocking IO calls, but it just did not work for me - maybe I did not take enough time to figure out properly. On the bus, however there is always a response for every command, so the host has ways to find out if a command succeeded or not. I started my network with owfs but as it was unreliable (I did not know if a write was succesful or not or took a lot of time to read back the register from the bus) I ended up communicating with owserver over IP, - where you get the response for everything properly - instead because I needed the feedback to retry or bail out. This approach proved very reliable I have been using it to control a gas furnace for over 4 years practically bus error-free. You can of course use owlib directly (I my case it was ruby with no lib available). 3. Watch ESD! Your 1-wire network will likely be a big antenna in the house, so it will pick-up an ESD event sooner or later. On my bus every single device was killed by a nearby lightning strike I had to replace all of them. It does not need to hit in directly to cause damage. Using the 1-wire bus ESD separator actually saved my computer as it separated it from the bus electrically! After replacing it I made an opto-isolation to be even safer. So if your network/equipment is critical (as mine is with the heating and hot water) watch this aspect too. Hope this helps with starting a new project. Regards, Doma On 11/08/2012 08:43 AM, Attila wrote: Hi Guys, |
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