Pi Bridge Cable

Topics about the Hardware of Revolution Pi
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timjones
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Joined: 14 May 2018, 22:08
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Pi Bridge Cable

Post by timjones »

I understand that the PI bridge is RS-485, Ethernet, and some ID pins. However, lets say I need to located one IO Module in another enclosure. Is there any hardware in the connector, or how do I make a cable to allow modules to be located in another location.
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volker
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Joined: 09 Nov 2016, 15:41
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Re: Pi Bridge Cable

Post by volker »

well,
that is a clever thing, aint it?
....
So here is how we do it...
We use the sniff lines (digital lines) to eneble a neighbour in the right side. As soon as this neighbour is enabled it is talking through RS485 and telling which kind of module it is and it gets its own bus address. Then this module does enable its right neighbour.... and so on... until no module is answering on the sniff line... then we know that we have reached the end of the chain.
Same thing is then done on the other side of the revpi Core but slightly different in the use of the sniff lines (because a module can be used on both sides and thus you cannot just mirror the lines).

nice idea, right? :idea: :idea: :idea: :D
Unser RevPi Motto: Don't just claim it - make it!
timjones
Posts: 14
Joined: 14 May 2018, 22:08
Answers: 0

Re: Pi Bridge Cable

Post by timjones »

volker wrote: 08 Jun 2018, 18:35 well,
that is a clever thing, aint it?
....
So here is how we do it...
We use the sniff lines (digital lines) to eneble a neighbour in the right side. As soon as this neighbour is enabled it is talking through RS485 and telling which kind of module it is and it gets its own bus address. Then this module does enable its right neighbour.... and so on... until no module is answering on the sniff line... then we know that we have reached the end of the chain.
Same thing is then done on the other side of the revpi Core but slightly different in the use of the sniff lines (because a module can be used on both sides and thus you cannot just mirror the lines).

nice idea, right? :idea: :idea: :idea: :D
Yes that is very clever! :D

One more question in that regard. What happens if the connection was disconnected/reconnected on one segment? How does each device know that part of the chain was broken request another address?

Finally, so technically making a cable wouldn't be a problem then right? If I have a gateway, I would need twisted pair for the ethernet lines correct? Do you know where I can find the bridge male connector so that I can make a cable?
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volker
Posts: 1046
Joined: 09 Nov 2016, 15:41
Answers: 1

Re: Pi Bridge Cable

Post by volker »

1st: breaking the line? are you talking about run time? Please note that PiBridge is not hot pluggable. You need to set up the installation and only after having done that switching on the power. You devices might even be destroyed by deliberately plugging the PiBridge on and of during devices which are under power. So please do NOT do this.
2nd: No using cable is not a good idea! The Ethernet channels are not standard Ethernet on the physical layer but they are without magnetics (capacitive coupling). Therefore the length of the bus is limited to 5 devices per side (which is about 8 cm of bus length). The back plane bus is also not ESD protected and using cable would be a big risk to get ESD problems. Last but not least your EMI will get horrible and the system will not stay in the limits of CE conformity.
Unser RevPi Motto: Don't just claim it - make it!
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