Unable to establish communications with Omnistat2.

[123]

I just installed a new HAI Omnistat2 RC-2000 in my home and it works properly as a standalone thermostat and drives my HVAC system consisting of a single-stage gas furnace, humidifier, and AC unit (December in Montreal so the AC unit remains untested). However, I'm having difficulty establishing serial-communications between it and my PC's Home Automation software (i.e. it is not connected to an OmniPro panel).

• I made a serial-cable as per Appendix B of the "Serial Protocol Description" document. For a DB-9 Female connector:
  Pin 5 (GND) connects to N/C.
  Pin 2 (RXD) connects to BLACK.
  Pin 3 (TXD) connects to GREEN.
  Pin 4 (DTR) connects to YELLOW.
  Pin 4 is also shorted to pins 1 and 6.
  Pin 7 is shorted to pin 8.
  FWIW, I triple-checked the serial-cable connections and I'm confident the cable and connections are fine.
• I removed the u-shaped jumper from the right-hand connector as per the instructions on page 15 of the document.
• I left COMM Jumper J8 in place.
• I set the System Baud to 300 and left the Expansion Baud at the default 1200.
  QUESTION: What is the difference between these two parameters? Which one is for communications with a PC? I'm assuming it is System Baud.
• The serial-cable is connected to a Digi EdgePort/8 which is an 8-port, USB-to-serial-port device. It is seen as COM6.
  QUESTION: Could the thermostat be unhappy with the TTL-level voltages (5V) furnished by USB/serial-port converters? Must it see 12V?
• I set my PC software to drive COM6 at 300 baud, 8-bit, no parity, 1 stop bit.
• My PC software allows me to observe serial-port communications. Transmitting a "Poll for Group 1 Data" command ("010203") results in no reponse from the thermostat, not even a "Negative acknowledge". As an experiment, I changed COM6's Baud Rate to 1200 but it did not correct the problem.

What have I overlooked or what should I try differently?

 

[BryanE]

Try removing the left COMM Jumper J8.

 

[123]

Thank you, BryanE! Your suggestion did the trick.

I've confirmed that my HA application is now successfully receiving the Omnistat2's status. I used its driver to alter the Fan Mode and the thermostat responded immediately. I'm a happy camper.

Maybe the documentation I have is outdated, or I just can't see straight, but I could not find any reference to removing the J8 jumper. I had nothing to go on so I followed the instructions for an OmniPro panel (says to keep J8 in place).



PS, any ideas about the difference between System and Expansion Baud rates? System Baud appears to be the one I need to communicate with my PC ... so what is the purpose of Expansion Baud?

 

[BryanE]

Thank you, BryanE! Your suggestion did the trick.

Glad to hear that worked.

Maybe the documentation I have is outdated, or I just can't see straight, but I could not find any reference to removing the J8 jumper. I had nothing to go on so I followed the instructions for an OmniPro panel (says to keep J8 in place).

It's not you... I'm not sure why HAI doesn't list this in BOLD in their setup guide.

PS, any ideas about the difference between System and Expansion Baud rates? System Baud appears to be the one I need to communicate with my PC ... so what is the purpose of Expansion Baud?

System is the important one. Not sure what Expansion does either.