26. February 2016

Hydra

Hydra Overview

How does Hydra work ?

Hydra connects to the KNX®-IP-interface as a “normal” client that “speaks” the KNX®-tunnel-protocol.
After receiving a positive connection response, Hydra sends heartbeats (connection state requests / responses) to the interface.
The connection to the IP-interface is established. Now Hydra opens a listener channel for the clients.
After a client has sent a connection request, Hydra answers with a connection respone and stores all necessary client-parameters in order to handle each client-request in the right manner.
The KNX®-tunnel-protocol uses different handshake-algorithms. The difficulty is, that a client should only gets the data dedicated to him, i.e. client 1 should not receive a response from a request by client 2.
Hydra solves this problem in storing any parameter and status of each client, e.g. when Hydra received a tunnel request acknowledege from the interface with sequence 23, Hydra opens a dictionary to lookup the right client waiting for this sequence.
Asynchronous responses, e.g. responses to a group read will be forwarded to the client who exactly waits for this response on this groupaddress
Furthermore all group writes from the KNX®-bus will be forwarded to all clients as indications .

Limitation
  • Only the tunnel-protocol will be supported, no device configuration of the IP-interface, no USB- or serial adapters
  • Only 3-ary groupaddresses were supported