Ruben, Not RS232, use RS485. Note that a star configuration is both and bad. Bad because you can't terminate the connections which can cause huge amounts of grief, really good because each link is separate - if one goes down, the rest still work. I've recently built a house and was planning to route the lines serially from point to point, however decided star was a better choice. In my case, I plan to power some devices from extra pairs in the CAT5/e/6 cable. Having only one device present makes this option viable. In terms of cable, the way my house is laid out and the prospective locations, very little ($) extra wire and effort was required for a home run system. You will probably need to create some sort of a "hub" device that takes these circuits and properly terminates each one. One PIC with a pin devoted to each link is sufficient. The hub could also be used for the aforementioned power distribution as well. The actual protocol is up to you. Ken ----- Original Message ----- From: "Ruben vd Merwe" To: Sent: Thursday, June 05, 2003 7:28 AM Subject: Re: [PIC]: Home Automation with PICs > Thanks Lyle > > What are the possibilities for RS232 or 485? By the sounds of it I might > have to go to a type of star config, as all my nodes will collaborate in > one place. > > Ruben > > -----Original Message----- > From: Lyle Hazelwood [mailto:haze9844@BELLSOUTH.NET] > Sent: 05 June 2003 12:55 > To: PICLIST@MITVMA.MIT.EDU > Subject: Re: [PIC]: Home Automation with PICs > > >On Behalf Of Ruben vd Merwe > >Subject: Re: [PIC]: Home Automation with PICs > > > >Thanks for all the feedback. > > > >I am just starting to build a new home and I am building it with HA in > >mind, meaning that all electrical systems would be able to be wired up. > >I have been investigating all the different systems, and I must agree > >that X-10 is way out there. > > > >I have currently got a system that I made which is working fine, but > the > >problem is that is a parallel bus system. So all the connected items > >have to be wired back to the control system. Where a serial system can > >have controllers all over the place and devices just wired to the > >closest controller. > > CAN is not quite that easy. It is serial, but there is a single run that > includes all nodes. There can be no "forks" in the line, and only two > endpoints. star configuration is not possible as far as I know. > > >I am keen on I2c and maybe CAN, and I like the IP idea, but as pointed > >out, expense in doing so. > > I am not very familiar with I2C for this kind of application. I believe > it was designed for connecting chips within a product. I am skeptical of > how well it could handle the noise you might pick up if you wired it > around > the house. I considered IP, but the cost per node, cost of hubs, and > higher > levels of "software overhead" made it less attractive. > > Some advantages of CAN: Most of the protocol overhead is built into the > 18Fxx8 PICs. Only an 8 pin line driver is required at each node for > interface. > CAN was designed to work in noisy environments. Automatic priority > arbitration. > Flexible addressing scheme. Well documented interface. 2 wire > bi-directional. > Automatic error detection and re-transmission, simple twisted pair > wiring. > Faulty nodes are automatically "kicked off" the bus. > > Disadvantage of CAN: maximum 8 byte packets. > > >Some more input welcome. Thanks for all the cool replies so far! > > >Ruben > > I should mention here that wireless CAN is available. Mr. Danmeyer has > created > http://www.autoartisans.com/products/index.htm > in case you need to go wireless. I have not used these (yet), but it's > nice > to know. > > There are many projects using CAN on the web. Example code for a CAN > node > and > a CAN bootloader are available from the Microchip "Application Maestro". > I'm > working with this now, though I haven't made it to the CAN code yet. > > Good Luck, > Lyle > > -- > http://www.piclist.com hint: To leave the PICList > mailto:piclist-unsubscribe-request@mitvma.mit.edu > > -- > http://www.piclist.com hint: To leave the PICList > mailto:piclist-unsubscribe-request@mitvma.mit.edu > -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu