I have a question in the networking section discussing protocols so I don't want to get into that here.
To the honest it raised as many questions as it answered but that may be a good thing....
So electrically speaking I want to have some/many devices on a buss of some sort.
It needs to be using cat5 which will carry data, one pair, audio, one pair and power, two pair.
The power can be used as a reference if needs be.
Now Obviously I could use 485 and buy tranceevers but from what I have read I don't believe it will work in a star topology basically because I can't keep weddings termination resistors.
I may have only understood the highlights but I think I understand that unterminated legs will reflect and generate issues.
Could I buy / build a 485 hub to fix this and if so would it be transparent ore would it device and then subsequently retransmit packets?
I am working with Arduino... Could I simply, ok perhaps not simply, build a bus using line drivers and if so given that I will want modest distances, perhaps as long as 50m, what electrical considderations are there.
Should I considder keeping TX and RX discriminated so that all buffers are one way. 232esque.
I may want to colossian check bit by bit - Is a high pulled low a practical solution to potentially having multiple drivers talking, even if it is only for part of an address word.
Should I be thinking about current or voltage... I assumed that there could be significant delay whilst a couple urgent pulse rises against parasitic inductance but I also realise that there is always current. I suppose what I am. Asking is how to minimise rise time on long legs.
As I said I realise that the hardware is only part of the story but the software is more flexible so it seemed reasonable to look purely at signals Jon this question as opposed to getting into protocol layers.
RE protocol, just to clarify,
Everything needs to listen to everything all the time.
Something, as they undecided, will prevent more than one device talking at a time.
Is there a hardware spec that will do this already? I ask because buying drivers may be a sensible option.
Is there any reason I can't simply pull up a line, in the hub and at its termination, and then pull out down with an open collector output when encoding data. would doing this with reciprocal lines and detecting Colossians using LoLo have any advantage, electrically.
I realise that the protocol will have an effect on these answers but I have to start somewhere so begining with some decisions, or at least options, for the hardware layer seems a reasonable plan.
Lastly, I suppose in absolute terms this does not need from be fast but I would like to explore predoctoral speed limits once I have a shortlist of possibilities.
Thoughts?
Thanks,
Al
To the honest it raised as many questions as it answered but that may be a good thing....
So electrically speaking I want to have some/many devices on a buss of some sort.
It needs to be using cat5 which will carry data, one pair, audio, one pair and power, two pair.
The power can be used as a reference if needs be.
Now Obviously I could use 485 and buy tranceevers but from what I have read I don't believe it will work in a star topology basically because I can't keep weddings termination resistors.
I may have only understood the highlights but I think I understand that unterminated legs will reflect and generate issues.
Could I buy / build a 485 hub to fix this and if so would it be transparent ore would it device and then subsequently retransmit packets?
I am working with Arduino... Could I simply, ok perhaps not simply, build a bus using line drivers and if so given that I will want modest distances, perhaps as long as 50m, what electrical considderations are there.
Should I considder keeping TX and RX discriminated so that all buffers are one way. 232esque.
I may want to colossian check bit by bit - Is a high pulled low a practical solution to potentially having multiple drivers talking, even if it is only for part of an address word.
Should I be thinking about current or voltage... I assumed that there could be significant delay whilst a couple urgent pulse rises against parasitic inductance but I also realise that there is always current. I suppose what I am. Asking is how to minimise rise time on long legs.
As I said I realise that the hardware is only part of the story but the software is more flexible so it seemed reasonable to look purely at signals Jon this question as opposed to getting into protocol layers.
RE protocol, just to clarify,
Everything needs to listen to everything all the time.
Something, as they undecided, will prevent more than one device talking at a time.
Is there a hardware spec that will do this already? I ask because buying drivers may be a sensible option.
Is there any reason I can't simply pull up a line, in the hub and at its termination, and then pull out down with an open collector output when encoding data. would doing this with reciprocal lines and detecting Colossians using LoLo have any advantage, electrically.
I realise that the protocol will have an effect on these answers but I have to start somewhere so begining with some decisions, or at least options, for the hardware layer seems a reasonable plan.
Lastly, I suppose in absolute terms this does not need from be fast but I would like to explore predoctoral speed limits once I have a shortlist of possibilities.
Thoughts?
Thanks,
Al