+- Comfort Automation/ Security System Forums (https://www.comfortforums.com)
+-- Forum: Third Party (interfacing to Comfort) (https://www.comfortforums.com/forum-5.html)
+--- Forum: KNX (EIB) (https://www.comfortforums.com/forum-12.html)
+--- Thread: Reading values back from Comfort (/thread-2239.html)
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- ident - 04-20-2011
Yes you can do
If Security Mode = Off
then Reset System
Endif
If the system is reset while the security is armed, after reset it will re-arm to the same security mode
- TheMax74 - 11-02-2011
Hello, i\'m interested too in reading comfort zones from Gira homeserver or any other external device.
Maybe you can implement a simple way to re-send all mapped zones (like when you reset comfort) by reserving a mapped group address to do it.
- ident - 11-02-2011
Perhaps there is a way to send a message to reset the UCM/KNX so it can resend the zones
- ekarak - 05-23-2012
Hello good people at Cytech!
Regarding the alarm & zone status updates to the KNX bus: it is essential that the UCM/KNX responds to status reads. I\'ve noticed in large installations (>16 zones) that packet drops are possible, thus you cannot be certain if a zone is open or not (so as to show it on a KNX touchpanel). UCM/KNX has to be more frugal regarding the sending of bursts of packets on the KNX bus. Thus, if a KNX screen displays all zones on a floor it could query the bus for the zone status.
Responding to KNX READ request packets shouldn\'t be too hard to implement (if UCM/KNX has its own CPU and memory, why not?).
- ident - 05-23-2012
Perhaps it may be possible for the UCM/KNX to respond to read requests from the Bus
However in your example if a KNX screen shows many zones and you query each zone for its status then that is going to cause a lot of traffic on the bus which itself may cause more problems
Our understanding is that KNX has a mechanism to do error correction so should not drop packets to cause zones status to be incorrect?
- ekarak - 05-23-2012
The KNX standard states: no more than 3 retransmissions for a failed transmit with random back-off delay (not exponential like Ethernet!), so: Yes it\'s possible for a poorly programmed device that floods the bus to saturate it.
That\'s the reason why in practice most KNX devices have a \"maximum transmissions rate\" parameter, typical value set to something like 30 packets / 15 sec., as well as a \"wait timeout before reading initial values from the bus\" so as touchscreens coming alive after power failure to wait a little before querying e.g. temperature sensors.