[download] Module: HAI Omnistat thermostat


Senior Member
File Name: Module: HAI Omnistat thermostat
File Submitter: 123
File Submitted: 7 Oct 2009
File Updated: 7 Oct 2009
File Category: Premise
Author: PFriedlander
Contact: None
Version: 1

Original Author: PFriedlander
Original Creation Date: 10-17-2003

From the original Premise Support Forum: [URL="http://forums.premisesystems.net/forums/400/ShowPost.aspx"]http://forums.premisesystems.net/forums/400/ShowPost.aspx[/URL]

This Module-based driver supports a single Omnistat thermostat via RS-232.

I believe this driver was written for HAI Omnistat RC-series thermostats circa 2003 (i.e. 80,90,100,etc) The attached zip file contains the XDO file and driver documentation. I've also added the RC-series Protocol documentation (circa 1998) and cabling pin-out.

Click here to download this file


Active Member
Totally off topic question, but is the Omnistat protocol the same or similar to the RC series thermos?


Senior Member
One and the same.

I just did a quick comparison of the old protocol document (circa 1998) with a more recent version (2008) and they share the same operating principle, packet format, and basic list of commands.

Naturally, the current protocol spec has probably been enhanced (new commands) to accomodate new functionality found in the Omnistat RC-1000/2000 series thermostats.
  • The old doc refers to a command to retrieve "Group 2 Data" but indicates this data is not yet defined. The current doc defines what is in Group 2 data and also describes Group 3 data.
  • The old doc describes the purpose of 73 internal registers whereas the new one defines 254 registers.
  • The purpose of registers 0-17 appears to have remained the same.
  • Registers 18-20 now serve a different purpose.
  • Registers 21-32 now hold the thermostat's Monday schedule whereas they used to define the schedule for weekdays.
  • Register 57 now handles outside humidity whereas the old doc indicates it is reserved.
  • Registers 59-73 appear to have remained unchanged.
  • The old doc lists all the supported thermostat models represented by register 73. The new doc lacks this useful bit of info.