alexxx
Advanced Member level 4
Hello.
I need to implemented an RS-485 network (because at least 400m are required without repeaters at 115200bps) with 100-120 nodes. The network must be open circuit tolerant, so this means that if a single cable cut takes place, the network should continue operating normally. So the obvious way to go is with a ring topology, where every node has two RS-485 ports, one connected to its “left” node and one to its “right” node. If the “left” node sends data that are not intended for my address, I will read it from the “left” RS-485 port and forward (retrasmit) the message to the “right” node through the “right” port, in order for the message to continue its “journey” on the ring. The network must be multi-master, because any node can send data to any node.
The tricky part is that there will be some alarm messages, so one of those nodes must be a network “manager”, checking that those critical messages will reach all destinations. If not, a fault condition should be indicated to the user, in order to inform that not all nodes took the message.
I did some digging and most references suggest a token ring topology, but I am not sure because if an alarm is initiated to a node, I need this node to instantly send this alarm to the network and not wait for the token to be cycled back to it. There are also plenty of other scenarios to be concerned about, like if an alarm condition takes place to multiple nodes at the same time, which they start transmitting it almost simultaneously. So this "network manager" issue troubles me even more and gives me doubts on which is the optimum way to go.
This is the scenario. I continue with my research, but if someone has implemented something similar, it would be great to hear his story or get a reference that I have not yet found, to point me to the right direction.
Thanks in advance.
I need to implemented an RS-485 network (because at least 400m are required without repeaters at 115200bps) with 100-120 nodes. The network must be open circuit tolerant, so this means that if a single cable cut takes place, the network should continue operating normally. So the obvious way to go is with a ring topology, where every node has two RS-485 ports, one connected to its “left” node and one to its “right” node. If the “left” node sends data that are not intended for my address, I will read it from the “left” RS-485 port and forward (retrasmit) the message to the “right” node through the “right” port, in order for the message to continue its “journey” on the ring. The network must be multi-master, because any node can send data to any node.
The tricky part is that there will be some alarm messages, so one of those nodes must be a network “manager”, checking that those critical messages will reach all destinations. If not, a fault condition should be indicated to the user, in order to inform that not all nodes took the message.
I did some digging and most references suggest a token ring topology, but I am not sure because if an alarm is initiated to a node, I need this node to instantly send this alarm to the network and not wait for the token to be cycled back to it. There are also plenty of other scenarios to be concerned about, like if an alarm condition takes place to multiple nodes at the same time, which they start transmitting it almost simultaneously. So this "network manager" issue troubles me even more and gives me doubts on which is the optimum way to go.
This is the scenario. I continue with my research, but if someone has implemented something similar, it would be great to hear his story or get a reference that I have not yet found, to point me to the right direction.
Thanks in advance.