I also happen to know that Dalsemi have sold their 1-wire=81 parts for use in the automotive sector, so that's a 3rd one! :-o -marc On 13/6/03 13:14, "Igor Pokorny" wrote: > Guys, >=20 > there is another standard in an automotive industry, especially in Europe= . > It's called LIN http://www.lin-subbus.org > One wire bus, rather slow with one master. It's supposed to be connected = to > CAN. >=20 > Igor >=20 >=20 > -----Original Message----- > From: pic microcontroller discussion list [mailto:PICLIST@MITVMA.MIT.EDU]= On > Behalf Of Alan B. Pearce > Sent: Thursday, June 12, 2003 10:13 AM > To: PICLIST@MITVMA.MIT.EDU > Subject: Re: [PIC]: Home Automation with PICs >=20 >=20 >>> Yes but isn't the CAN version used in cars the kind with one wire and >>> shared ground ? I am under this (strong) impression. And so are most >>> interface chips. >>=20 >> I don't know. That's possible since every penny counts and they can >> afford a slow bit rate, but I would have expected differential due to hi= gh >> noise environment. All the CAN driver chips I've seen are differential, >> and this is what is described in the standard as I recall. However, tha= t >> is merely one implementation of CAN in any case. >=20 > Looking at the CAN driver schematics I can see why Peter thinks they may = be > a single ended system. It would appear that they are not a "true > differential" drive with one side going to both positive and negative > voltages. The driver chip has a transistor which pulls the CANH line to > positive, and another to pull the CANL line to ground, but it looks like = the > "other" state is open circuit. It would seem the receiver is a true > differential item with the threshold set high enough to minimise receivin= g > any noise. >=20 > .... >=20 >>> The kind of CAN that is most commonly used is the one wire plus ground >>> kind. Twisted or not. And it does not like transients. The open >>> drain/bit squashing part that does the arbitration requires that the >>> bus be relatively high impedance at least part of the time. >>=20 >> I haven't seen that type of CAN system. All this proves is that it's >> possible to create bad implementations of CAN (I'm not even sure this >> would be true CAN anyway). I was objecting to your statement that CAN >> inherently has these problems. CAN is designed to work with differentia= l >> signals, and this is widely supported by various semiconductor >> manufacturers, including Microchip. I'm quite sure Phillips has a can >> driver chip similar to (probably even drop in equivalent) to the MCP2551= . >> I think Microchip is merely a follower here. If I remember right, they >> claim superiority in power consumption, but are otherwise trying to be a= s >> compatible as possible with industry standard CAN drivers. >=20 > I cannot see how it could be run as a one wire plus ground, and be called= a > CAN bus (see my email from yesterday). I have just had a look at the > Microchip MCP2551 and the Philips PCA82C250 and PCA82C251 transceiver chi= ps, > and they are indeed pin compatible. The MCP2551 is claimed to be suitable > for 12 and 24V systems, Philips only claim the PCA82C251 to be suitable f= or > 24V. Have not done a close comparison of the specs otherwise, but it woul= d > seem they are drop in replacements. >=20 > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics >=20 > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. >=20 =20 -------------------------------------------------- Marc Nicholas Geekythings Inc. C/416.543.4896 UNIX, Database, Security and Networking Consulting -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu