RE: RS485 resistors

["BUTLER, Tony, FM" <roaming@xxxxxxx>]

Okay thanks Ian.
I'll have a bit of a think before I do anything methinks......


Tony

> -----Original Message-----
> From: ian.bird@xxxxxxx
> [mailto:ian.bird@xxxxxxx]
> Sent: 15 August 2002 10:11
> To: ukha_d@xxxxxxx
> Subject: [ukha_d] RS485 resistors
> 
> 
> Hi Tony
> 
> If your wiring is short it probably won't matter. Neither 232 
> nor RS485 are
> protocols by the way. You might be down to trial and error 
> with a scope to
> find out what is going on.
> 
> I don't know the units so cannot help there I am afraid.
> 
> Ian
> 
> 
> 
> 
> 
> Hi Ian, 
> 
> Thanks for the info. 
> 
> These termination resistors are of concern - do you mean 
> there will be some 
> in the converter I need to disable (not a problem really) or 
> some in the 
> devices at each end I would have to disable? This _would_ be 
> a problem as I 
> don't want to take the chance of wrecking expensive kit!!! 
> 
> Good to know that 485 is robust enough if you don't connect things up
> properly but......what if it's _not_ 485? 
> Is there any way you can think of that I may be ablt to 
> dientify if it is 
> 232/485/any other serial protocol? 
> 
> thanks, 
> 
> 
> Tony 
> 
> 
> > -----Original Message----- 
> > From: Ian B [mailto:Ian@xxxxxxx] 
> > Sent: 14 August 2002 19:50 
> > To: BUTLER, Tony, FM 
> > Subject: RE: [ukha_d] Re: Displays round the house - 
> architecture... 
> > 
> > 
> > Hi Tony 
> > 
> > Assuming it is RS485 I would get one of the commercial 
> > converters but you 
> > will need to have access to the termination resistors 
> somewhere. These 
> > should only be applied at each end of the network. Ask if in 
> > doubt when you 
> > buy yours. RS485 has a plus and minus rail, plug it in 
> > wrongly and it simply 
> > doesn't work. Switch the connections and off you go. 
> > 
> > Other than that cut the cable and plug in. 
> > 
> > Ian 
> > 
> > >-----Original Message----- 
> > >From: BUTLER, Tony, FM [mailto:Tony.BUTLER@xxxxxxx] 
> > >Sent: 14 August 2002 09:13 
> > >To: 'Ian@xxxxxxx' 
> > >Subject: RE: [ukha_d] Re: Displays round the house - 
> architecture... 
> > > 
> > > 
> > >Hi Ian, 
> > > 
> > >> -----Original Message----- 
> > >> From: Ian B [mailto:Ian@xxxxxxx] 
> > >> I also have a 232 to 485 converter running as an
interface 
> > between my 
> > >> prototype networks :-)) 
> > > 
> > >This is of interest to me. 
> > >My Linn knekt system uses, I think (well, others think 
> > anyway) 485 because 
> > >power and data are sent over cat5 to wall moounted room 
> control units 
> > >(RCUs). 
> > >I would like to look at say using a PC to emulate an RCU 
> > and/or to send IR 
> > >for devices not supported by the version of Linn software
> > running on my 
> > >system. 
> > >Now Linn are about as open as Microsoft when it comes to 
> > divulging details 
> > >of their systems, so it's reverse-engineer or nothing. 
> > > 
> > >Anyway, to the point: To do this I would need to 'sniff' 
> > the signals being 
> > >sent to the RCU and to do this I would, I guess need to 
> > convert from 485 to 
> > >232 so the PC can see the data and later, if I get as far as
> > emulating an 
> > >RCU, I would need to do the reverse. 
> > >How easy/difficult is it to build such a converter? Does 
> > your one do both 
> > >way comms? 
> > >How easy do you think it would be to basically bung one in
> > >parallel with the 
> > >existing system so I can sniff the data being sent over the
> > 'live' system./ 
> > >I've seen 232 sniffers mentioned in places before, but I 
> > guess I'd need a 
> > >485 sniffer...... 
> > > 
> > >Any thoughts would be most appreciated. 
> > > 
> > >thanks, 
> > > 
> > > 
> > >Tony 
> 
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