Communication between M171ODM14R and M172PDG42R with modbus

[dmuzina]

Hello,

I need to exchange data between this two devices via modbus. Can someone explain it to me how to do it properly?

[Bastian_Schmitz]

Hi You could acitivate on TM172 in ESME HVAC in the configuration tab the Modbus Master functionality on RS485-2. After that you could add a generic Modbus Object and FC3 to read data from the TM171ODM14R. You could see the process in this video. The related Modbus Register for the IOs of TM171O are declared in the User Manual.

[dmuzina]

@Bastian_Schmitz  My 171O says that have only master configuration. I need it as a slave not master is that posibble?

[Bastian_Schmitz]

The standard firmware of TM171O offers the possibility to use a Modbus Master. But this function get only into account if you add messages to the Master tab and activated their the Master ability. 

If the master is not active you act as Modbus Slave. 

In that case are the Register addresses from Status, BIOS and EEPROM are read and write able via modbus.

Status variables could be configured as Readonly.

[dmuzina]

@Bastian_Schmitz I put another firmware 412.21 so that it can be slave only, because I didnt know about this information you mentioned above but still I can not get connection. I will put picture here how I made configuration so you can check and tell me if I made something wrong.

Slave M171 configuration:

Master configuration M172:

In M171 on address 9280 I have WORD variable configured with value 99 but I dont read anything.

[Bastian_Schmitz]

Hi, did you use RS485-2 on TM172? Did you check the wiring and try to change +/- ? Please disconnect with TM171ADMIN from TM171ODM14R if you want to connect via TM172.

[dmuzina]

@Bastian_Schmitz Yes I am using RS485-2. Wiring is good because i try this on my desk in office and need implement that on the field. I need connect 4 M171 as slave to M172 Master. So i try to make that connection im my office first. 

Yes I have also read that TTL communication can not work together with RS485 so I dissconnect from TTL and yuse just RS485 but without success.

[Bastian_Schmitz]

The response 2 is normally an indicator that there is a general communicaiton issue. Otherwise the response in sysMbmrtunodestatus would be higher. Do you use a 120 ohm resistor at on or booth ends of the line. Mostly it work on TM172 also without resistor, but not in any case.

You could also try to test the communication to TM171O via a USB/RS485 and a third party tool like Modbus Poll. This could be help to indentifie if the problem is on the side of TM172 or on TM171O.