RE: Loop connection

I don’t see this working in any reliable fashion. How will node4 decide to
turn on the switch? What happens if only one of the two CAN conductors is
disconnected/broken? What if the disturbance is not a clean cut? How should
the terminators be placed?

In short: it won’t work, instead of increasing the reliability you will end
up with something that is more error-prone.



I do see ways to design for redundancy/high availability. One way is to use
fault tolerant transceivers (that can survive a CAN conductor disruption or
short to ground/power), another way is to use two CAN interfaces per node
and redundant cabling (as is commonly used for vehicle network backbones),
optionally using different paths:



  T-+-----+-----+-----+-T

   |     |     |     |

  N.1   N.2   N.3   N.4

   |     |     |     |

T-+-----+-----+-----+-T



cheers,

Bram



From: [email protected]
[mailto:[email protected]] On Behalf Of Hideki
Masudaya
Sent: woensdag 1 april 2015 4:33
To: [email protected]; [email protected]
Subject: RE: [CANLIST] Loop connection



Thanks Allen



I'm Soory for bad my explain.

My thinking network is following.

Ring wireing on Sw box+node4

if Sw is turn off, (a) to (b) short wire is shut down.

(a) to (b) => (a) to (d) to (c) to (b)

if Sw is turn on , (a) to (b) short wire is conect.

Sw control is node4.

Each node conect branch from Ring wireing.

Terminator is include 2nodes.



If node4 turn on SW, CAN bus is Loop toporogy.

CAN bus is not defined Loop toporogy.

Why not?



Image of connection.

(d) ====================(a)

||  Ring Wireing                        || (SW box+node4)

(c)====================(b)

    ||                   ||               ||

node1           node2        node3…



Best Regards,

Hideki MASUDAYA



From: [email protected]
<mailto:[email protected]>
[mailto:[email protected]] On Behalf Of Allen
Pothoof
Sent: Tuesday, March 31, 2015 10:46 PM
To: [email protected] <mailto:[email protected]>
Subject: RE: [CANLIST] Loop connection




Are you talking about a ring topology: node 1 connected to node 2, node 2 to
node 3, node 3 to node 4 and node 4 back to node 1?

CAN is designed as a bus topology, where a node broadcasts it's information
onto a common backbone and other nodes can consume or ignore it, depending
on their needs.

In a ring topology, every node has to handle each packet that comes in and
forward it on to the next node.

If you took a CAN bus and "connected the ends together", what I suspect
would happen is that the nodes would go bus off fairly quickly due to bus
errors.  I'm not sure what kind of reflectance you'd get as the message
tried to "go both ways around the ring" and I don't know where you'd put the
terminating resisters (or if it even makes sense to talk about "terminating"
resisters).

In short, CAN is not designed to work in a ring topology.

Al.

  _____

From: [email protected] <mailto:[email protected]>
To: [email protected]
<mailto:[email protected]> ; [email protected]
<mailto:[email protected]>
Subject: RE: [CANLIST] Loop connection
Date: Mon, 30 Mar 2015 23:57:04 +0000

Thanks  Allen，



I am sorry for Mail title.

I forgot changing title.



I want to know pysical reason.

If I make Loop conectiion of CAN network,the system is not conection?

Or  comunication is still alive?



I think sytem node is about 4~8units.



Kind Regurds,



hideki MASUDAYA







From: [email protected]
<mailto:[email protected]>
[mailto:[email protected]] On Behalf Of Allen
Pothoof
Sent: Tuesday, March 31, 2015 6:07 AM
To: [email protected] <mailto:[email protected]>
Subject: RE: [CANLIST] Loop connection




 Hideki,

First of all, I've changed the subject title; it's not considered polite to
hijack other people's threads.

To your question as to why CAN "is not Specify Loop Type connection", bear
in mind that CAN is a broadcast network, not a point-to-point network.  As
such, it is somewhat akin to a radio: a node "broadcasts" it's data but
doesn't know how many other nodes are listening; it may be 1 or it could be
100.  If some number of those nodes go off-line or become disconnected, the
broadcasting node neither knows nor cares.  The only requirement is that
there must be at least 1 other node active to acknowledge the transmission.

Regards,
Al Pothoof

  _____

From: [email protected] <mailto:[email protected]>
To: [email protected]
<mailto:[email protected]> ; [email protected]
<mailto:[email protected]>
Subject: RE: [CANLIST] Busmaster CAN bus simulator -- "Function editor"
Date: Mon, 30 Mar 2015 08:44:10 +0000

Hello



I have a question  about CAN Netowork.

CAN Network is not Specify Loop Type connection.



I want to know why .

I  consider Redundant system of CAN Network.

If the system detect cutting CAN wire, the system connect another CAN wire.



Its system problem is ability of loop connection.



Kind Regurds,



hideki MASUDAYA