AVR-Chat

>>Ground wire *must* be used for reliability.
> 
> No, you are assuming that current will flow, I do design professional 
> equipment for a living, not just for my garage. If my equipment is not 
> line-powered then I like to opto-isolate the 485. How can current flow 
> in these two situations??
> 
>>>Anyway, I like the fact that you are not strictly abiding by the 
>>>standard and doing what engineers do best .... tinkering ;)
>>
>>I always work with known and bounded parameters. Never "tinker".
> 
> Call it what you will, this is like the chicken and egg thing. How do 
> you know and bound parameters unless you "tinker" in the first place????
> 
> 
> *Peter*
> 

I tend to play it safe in the middle, less grief. Eat my gruel, issue my 
invoices, eat.

I Use 232 for short hops & use  full 232 chips from AD or Maxim to spare 
customers the issues with half baked implementations that work with some 
desktops but not all laptops etc.

For 422/485 we always use a ground, as per manufacturers recommendations. 
However if ground lift is a problem then full iso is the way to go.  Nothing 
quite so satisfying as watching your ground lead convert to carbon and copper 
vapour when your data lead is by accident the earth reference for a 30KW 
induction heater and a similar sized pump in a nearby building.  Gives you an 
appreciation of why it is easier to play it safe & not skimp.

As for tinkering, I'm with Pete.  Might start the first 'look' in the sim or 
excel but the reality check is to build one and knock it about on the bench and 
follow it with the CRO. Besides, most of the time the bit you need to use 
doesn't have an accurate model anyway, most sims have a very long way to go yet 
;-) Again, a bit of each.

Using a solely theoretical approach assumes that you have a reasonable command 
of the facts at the time, I don't pretend to be that clever. The tinker approach 
makes no such assumption, it is a journey of exploration which often leads to a 
far greater understanding of both the operation and it's boundaries. Theory must 
also be included or else you are just swanning about on the bosses time.

Peter & I probably agree because we are self employed & make the time to 
explore. If I lose this curiosity, pull what is left of my shiraz soaked brain 
out & put me in sales.

-- 

Cheers  ( Long time no hear Pete ;-)

Don