RS485 resistors

[ian.bird@xxxxxxx]

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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