Trouble communicating with RC-2000 thermostat

[beelzerob]

I've rechecked the wiring scheme, and it matches what the protocol doc says in the back. I've verified the device address is 1.

So when I send the bytes:

010203

That should be requesting group 1 values for address 1, correct? I couldn't think of an easier or more foolproof way to verify communication is established.

Any help appreciated.

 

[beelzerob]

No one communicating with an RC2000 directly via PC?

 

[Brian Yokum]

beelzerob,

Are you sending the ASCII string "010203" (six characters) or are you sending the three characters 0x01, 0x02, and 0x03? The Omnistat2 protocol is a binary protocol and requires the three bytes, not the six characters. Make sure the communications mode is set to "SERIAL" and the baud rate is set correctly.

 

[beelzerob]

Thanks for the help Brian!

Ya, I sent hex bytes of (0x)010203.

I made sure it was set to serial and I changed the baud rate to 1200 in case the distance was too long for it (it's probably a 50 ft+ length of wire)

Love the thermostat, btw! Just need to talk to it now....

 

[Brian Yokum]

beelzerob,

When you use the Omnistat2 in RS-232 mode there is a jumper that needs to be removed. This is documented in the Omnistat2 installation manual. Depending on the revision of the thermostat you have, this jumper is either on the communications terminal block between the N/C and Black terminals or on the thermostat circuit board itself.

 

[beelzerob]

Hmmm... an excellent suggestion. There *is* a jumper on the circuit board, and I don't know what it's for. I did see the jumper on the wiring terminals, and at first I left it there, but then I went back and realized it was keeping my TX line tied up probably....so i removed THAT jumper. I'll look in the manual to see what that circuit board jumper is for.

 

[beelzerob]

Ok, I see it in the install manual. That's not the jumper I was thinking of, so I'll have to wait until I get home to see if that jumper is removed or not. Great tip, thanks.

 

[beelzerob]

Well, my circuit board definitely does NOT have that comm jumper shown in the manual. There's nothing there at all on that part of the circuit board. (board version 1.03 if that helps). So I guess that means the jumper on the comm terminals was the only one? I've already tried talking to it with that one removed.

Any other suggestions on how to troubleshoot this? Thanks for all the help so far!

 

[Brian Yokum]

Make sure your software is asserting DTR and that there are no gaps between the bytes that violate the timing specifications in the protocol document. Triple check your wiring and consider using an HAI RS-201 cable. Triple check the communications settings in the thermostat.

 

[beelzerob]

Good ideas, will do.

 

[beelzerob]

Make sure your software is asserting DTR

Bingo! Got a response. THANKS!!

 

[beelzerob]

Communication is going well now. However, I cannot seem to find any register to ask just to get a current status on what is actually going on in the system. (Is the fan on? Is a heating or cooling stage enabled?) I can only seem to ask what the system is SET to, not what it is actually doing. The only register I can think of that might hold that info would be "Current status of relays", but there's no indication how to interpret that value when it comes back.

Also, what exactly is the difference between current mode (61) and current mode (71)? I had thought maybe 71 would tell me what the system was currently doing, but so far it does not appear to....it says "Heat" even though the system is currently off.

Thanks for the help.

 

[Brian Yokum]

beelzerob,

You need to query the relay status register (72) to determine the current status of the system. If bits 1, 2, and 4 are clear, the system is idle. The system is also idle if bits 0 and 2 are clear and bit 1 is set. The system is cooling if bits 0 and 1 are clear and bit 2 is set, otherwise it is heating. You should check the bits in the order shown.

The system is humidifying when bit 5 is set and dehumidifying when bit 6 is set. Bit 3 is set when the fan relay is energized. The fan may or may not be running depending on the furnace controls. Some furnaces require that the fan relay be energized when calling for heat, others don't. The furnace can also inhibit running the fan until the furnace has heated sufficiently.

Register 61 shows the current system mode setting. When set to auto, register 71 indicates whether the system most recently changed over to heating or cooling.

 

[beelzerob]

Awesome awesome awesome. Thanks Brian. :horse:

 

[beelzerob]

Grabbing for all the info here while I can.....

Is there a specific bit for when it's using 2 stages of heat? Or emergency heat? The more resolution I can get on what the system is doing, the better.

As far as humidity....the value that comes back from "current indoor humidity", is that 0 to 100 percent? Just a guess....