3 Replies Latest reply on Jun 12, 2014 7:01 AM by user_14586677

# Implementing cypress Repeater Algorithm if the communication is not 100% theorically perfect.

Hi everyone,

I am considering implementing Cypress repeater Algorithm for PLC (AN62487). My doubt is if we have 15 slaves and the repeater reaches not just 1 node next to it but 2 or more nodes and if we don't have 100% reach ability node-to-node (less say it could take 1-3 messages before one node reads correctly a message).

According to the explanation of AN62487 document on page 2-3 it seems that if a repeater message reaches 2 nodes ahead of it, the 2 node will stop repeating the message because both receive a confirmation from each other and plus the nodes ahead of these 2 have not received the message yet due to the fact we don't have 100% reach ability.

Here I try to explain the scenario trough a scheme:

A--B--C--D--E--F--G--H--I--L

A wants to communicate with L.

A has sent direct message to L, which can't see A, A sends broadcast message.

After direct message to L, both send broadcast message. Both receive a confirmation from each other so they stop repeating the message.

Now, if none of the further nodes ( D,E, ...) has received the broadcasted message from B and C (bad luck), the message is lost and never reach L.

My question is: Does the algorithm works if a node next to another does't received with 100% certainty a message.

Thank you in advance for the support.

- J
• ###### 1. Re: Implementing cypress Repeater Algorithm if the communication is not 100% theorically perfect.

Seems to me the algortithim has each node operating as a repeater

requiring acknowlegement, and each node repeats to its neighbor until it

achieves acknowlegement. So the packet propagates to each nearest

neighbor until complete.

Regards, Dana.

• ###### 2. Re: Implementing cypress Repeater Algorithm if the communication is not 100% theorically perfect.

I think that with the number of hops value in the packet eliminates my doubt about the message reaching more than 1 neighbour node.

Now I am concern about the case 2 nodes send at the same time a packet. Will the packets collide and be destroyed?

Thank you again, your help is appreciated !!

- J

• ###### 3. Re: Implementing cypress Repeater Algorithm if the communication is not 100% theorically perfect.

Use CSMA in the protocol, much like Ethernet, to avoid collisions.

Regards, Dana.