TM172P TM172E Can Communication

[Diegomb20]

Hello,

I am trying to communicate the PLC (TM172PD28R) and expansion module (TM172E28R) which are in different cabinets and powered by two different DC power supply (ABL2REM24015K). The cable is capable to transmit RS485 signals (120 characteristic impedance) and the distance is about 50m. I connected the Gnd shield to both end (PLC and controller), set dip switch 1 of expansion module to ON to activate EOL resistor and put a 120Ohm resistor in PLC side between L and H. Dip switch 2 and 3 were set according to the speed configured in the ESME HVAC. Dip switch 4, 5 and 6 are all Off (Address =1)The led in the expansion module flash for a moment at power on and then stay on. I tried 250Kbps and 125Kbps without success. I checked the communication using the target variables sysCANOpenNodeStatus and sysPeripheraStatus. Am I missing something in the configuration?.

[Conair_Ian]

Hello. I have a similar setup operating with the only differences being the following:

- My system is setup on 500kbps

- I do not have a resistor on my TM172PDG42RI

I have 2 separate machines done this way without issue.

[Bastian_Schmitz · Accepted solution]

Did you made a download all? Only in that case the Connec.par file will be written to the controler. This file is mandatory to start the communication. Regarding CAN it is also good to perform an complete restart of plc and expansion. The PLC send a boot command via CAN to the expansion. This happens only via startup. To perform a real restart I would suggest to unplug a USB communication cable and to remove the power connector. Please don´t unconnect only 24V +/- on the PLC or the expansion. That could be generate problems if GND is connected. 

[Diegomb20]

Hello Bastian,

That was indeed the solution. Even if you make a download all or send de Connec.par in the commisioning tab the PLC the communication didn't establish. I had to power cycle the PLC to make the communication working. It is weird that this is not specified in the manual neither of the PLC nor of the extension module.

Thank you for the help.

Regards.

[Bastian_Schmitz]

The problem could be the way how you communicat with the PLC. If you are connected via MiniUSB the processor of the PLC is supplied via the 5V of the USB. This could be a problem in some situations for a real restart. If youe are connected via Ethernet this problem should not occure.