Convert 9pin RS232 to Loxone RS 232 extension

[Gast]

Hi All,
I am trying to include my Zehnder MVHR into Loxone and struggling! I have translated the German posts but there seems to be a significant difference between the Zehnder ComfoAir350 and ComfoAir550.
I only have access to the connections motherboard not the main control board and thus cannot use an RJ45 jack. I can plug into an RS232 port but don't know which Pins to connect to the Loxone RS232 extension. Can anyone help? After that can anyone help with programming?
Thanks,
Jim

[Thomas M.]

pinout of the extension ...
https://www.loxone.com/dede/wp-conte...-Extension.pdf

and the 9pin-dsub plug pinout ...
https://kompendium.infotip.de/files/...01_03_Pins.gif

attention:
TX (transmit data) of the extension is wired to the RX (receive data) of the device
RX of the extension to TX of the device

[Gast]

Thank you Thomas, Are you familiar with Zehnder?
So which pins go to which?
Am I correct:
I can see pin 5 is ground so Pin2 Receive data goes to Loxone TX and Pin3 Transmit data goes to Loxone RX
Does there need to be a positive supply or not and if so where should this come from and go to?

[Gast]

I may try my luck on the German side of the forum as well.

[Thomas M.]

i mentioned it already

yes:
Pin 5 ("GND Zehnder") to GND Loxone
Pin2 Receive data goes to Loxone TX
Pin3 Transmit data goes to Loxone RX

there ist no additional connection (i.e. power supply) necessary between zehnder and Loxone extension.

[Labmaster]

1. only connect RX, TX and GND, no positive supply
2. make sure there is not other device connected, only the Zehnder ComfoAir and the RS232 extension.
3. there will be no trafic on the bus as long as not data is sent by the RS232 extension, as the Zehnder ComfoAir will only send data on request. If there is trafic without request by teh RS232 then there must be another device on the RS232 line, make sure then, that this device will be disconnected when using with RS232 Extension. RS232 is not a BUS, it is a Point to Point connection, where each side has its dedicated transmit and receive line. For a RS232 connection It is not allowed to put more than one transmiter on the same line. (this will violate the electrical specification and may cause damage over time)

[Gast]

Hi Labmaster,
I am learning from the German forum as well! It looks like lots of people have wired the Loxone into the same connectors with the ComfoEase and they get some interference. This would explain what you are telling me. Do you think I should disconnect the comfoEase and wire the loxone into these green blocks rather than trying to work out the pins on the sub-d?
Could I use RS485 instead? Or is this silly because it is still 232 in the zehnder?
Jim

[Labmaster]

The electrical spezification on the Zehnder is RS232 and not RS485.
You could solve the electrical problem (not stressing the hardware over time) by using RS232 to RS485 converters on all endpoints (ComfoAir, ComfoEase, Loxone RS232/ directly Loxone RS485)
Electricaly RS485 builds a Bus system where a collision (more than one transmitter sets different levels on the line) will not cause a type of shortcircuit.

But even with this, what would not be solved, is the protcol Problem itself, as it runs on a point to point connection (RS232) so Zehnder had not to take care about collision handling.
So even with RS485 or any other type of Bus coupling you might whant to care about this issue then.

The ComfoEase normaly request data from the ComfoAir in more or less time scheeme where it then gets data back from the ComfoAir.
If you only need to read data that are alread on the bus, then this is easy as you could simply hear all data that are requested and sent back to the ComfoEase.
If you nee to request own data or you want to write otherwise to the bus, then have to find free time slots on the bus.

If you could live with a sometime not 100% working ComfoEase then a simple solution to the protocol problem is to retry as often as neccessry to get valid data.
But this solution i would only recomend if the electrical issue are solved, as any collision may damage the hardware, the more this happens the earlier it might fail in the future.

[Gast]

Hi Labmaster,
Thank you for this information. I think that the best way for me to proceed is to remove the comfoEase completely and connect Loxone into the Zhender in the Ease terminals.
So now I must think about programming a bit more.
I know that I can set the three fan speeds and set the Zehnder to holiday mode.
What I don't know is how to ask for temperature information from the Zhender and then control the 'baffle' for summer time when it is hot.
I also have a humidity probe attached to the Zhender control board so I need the Loxone to have this information to change the fan speed up when showering.
I also don't know what else I need to program into the Loxone. Presumably the air volume and other basic set up is already in the ComfoAir after it was input through the comfoEase?
Thank you again,
Jim