README
¶
What is 'gofinity'
Gofinity is a library for interacting with the Carrier Infinity / Bryant Evolution communicating residential HVAC systems.
This library exports
- Bus communication snooping / decoding
- Bus device state tracking
- Tools to help support reverse engineering device communications / internals
The code in this repository can loosely trace it's heritage back to Andrew Danforth's Infinitive project which aims to emulate a SAM device.
History
This project has evolved out of my desire to data-log everything on my HVAC system. I'm particularly interested in:
- logging all temperature sensor data (my outdoor unit is always wrong when it's a sunny day) and correlating it with 3rd party metrics / measurements (weather stations).
- logging BTUs produced / moved by the system.
- logging energy consumption.
- Calculating the effective R-Value of my building envelope.
Longer-term, I want to be able to:
- Control my system like a SAM. (but have it actually work with Bryant systems)
- Segment the RS-485 network to interdict system commands to subordinate devices.
- Create a zoning control module.
- Build an 'economizer' module that transparently works in conjunction with the heat-pump.
I have a fancy hybrid heat pump & variable throttled furnace, and my utility company costs fluctuate enough that given specific environmental factors, it may be less expensive to use gas or electricity (heat pump) for heating. I also live in a very temperate zone of the north american continent, where for roughly 8 months of the year the outdoor ambient air could be used for cooling with a fan rather than running the compressor on the heat pump.
My night-time 'set back' with the thermostat in 'auto' mode results in my heat pump compressor activating, when I could economize with just ambient air from outside.
The HVAC company solution to outdoor air involves a heat exchanger to try to equalize incoming ambient air temperatures to the same temperature as the conditioned space. Using this system to try and 'cool' a home would result in the fan having to blow for considerably longer than otherwise necessary if conditioned air were simply exhausted and exchanged for ambient outside air.
This all came about, as a consequence of talking with my HVAC tech (whom I also know outside of his professional life) about my economizer idea. Turns out, there are commercial products out there that do this kind of thing, but they're pretty expensive and don't do a great job of integrating with the Carrier / Bryant communicating systems. My friend did the opposite of trying to talk me out of it.
Challenge Accepted.
Protocol / Device Information
Physical ABCD Bus
Half Duplex RS-485 + 24VAC = ABCD
Inside Carrier Infinity / Bryant Evolution systems there's a set of screw terminals labeled, "ABCD". These are the very wires which connect the thermostat, air handler, and any outdoor units (heat pump, air conditioner).
The A & B terminals carry RS-485 serial data at 38400, 8n1. The C & D Terminals provide 24VAC.
RS-485 Hardware
You'll need some way to communicate with the RS-485 bus of the ABCD connectors on your HVAC system. Instead of dealing with the shortcomings of common USB transceivers and looking more toward my final goals of embedded custom hardware & software, I designed and built pi485, a TTL Serial to RS-485 transceiver for Arduino and Raspberry Pi type devices. These are not difficult to make, and a full BOM will cost about $15 USD (2017 prices) in single quantities. You could probably do it for less than that if you have a bunch of things in your 'junk drawer'.
Or, you could go the RS-485 -> USB Converter route. Any of these can work.
Beware hardware that doesn't have a way to disable termination resistors, as that will cause issues with your ABCD bus. Also, devices which don't properly bias the AB lines with the DC supply voltage and 'ground', may have issues as well. These issues (and I wanted to use the UART rather than USB) were why I created pi485.
Protocol Basics
Bootup Sequence
Documentation
¶
Index ¶
Constants ¶
const ( READY = uint8(0x00) RUNNING = uint8(0x01) STOPPING = uint8(0x02) INVALID = uint8(0x03) )
Constants for Bus.status
const ACK = 0x06
const ERROR = 0x15
const READ_REQUEST = 0x0b
const WRITE_REQUEST = 0x0c
Variables ¶
var Operations = map[uint8]string{ ACK: "ACK", READ_REQUEST: "READ_REQUEST", WRITE_REQUEST: "WRITE_REQUEST", ERROR: "ERROR", }
Functions ¶
This section is empty.
Types ¶
type Bus ¶
type Bus struct {
// contains filtered or unexported fields
}
Bus defines frame-based interactions atop a Transceiver
func (*Bus) Probe ¶
func (bus *Bus) Probe(received OnFrameReceived)
type FileReplayer ¶
type FileReplayer struct {
// contains filtered or unexported fields
}
FileReplayer is a Transceiver that turns writes into 'no-ops', but allows for probing previously recorded bus logs. if a FileReplayer hits an EOF, it's considered no longer valid.
func NewFileBusReplayer ¶
func NewFileBusReplayer(file string) *FileReplayer
func (*FileReplayer) Close ¶
func (fb *FileReplayer) Close() error
func (*FileReplayer) IsOpen ¶
func (fb *FileReplayer) IsOpen() bool
func (*FileReplayer) Open ¶
func (fb *FileReplayer) Open() error
func (*FileReplayer) Valid ¶
func (fb *FileReplayer) Valid() bool
type Frame ¶
type Frame struct {
Header Header
// contains filtered or unexported fields
}
A Communication Frame (message)
func NewProbeDeviceFrame ¶
type Header ¶
type Header struct {
Destination uint16
Source uint16
Length uint8
Operation uint8
// contains filtered or unexported fields
}
A Frame Header
type SerialTransceiver ¶
type SerialTransceiver struct {
// contains filtered or unexported fields
}
SerialTransceiver is a Transceiver that operations on serial ports. Surprise!
func NewSerialTransceiver ¶
func NewSerialTransceiver(device string) *SerialTransceiver
func (*SerialTransceiver) Close ¶
func (st *SerialTransceiver) Close() error
func (*SerialTransceiver) IsOpen ¶
func (st *SerialTransceiver) IsOpen() bool
func (*SerialTransceiver) Open ¶
func (st *SerialTransceiver) Open() error
func (*SerialTransceiver) Valid ¶
func (st *SerialTransceiver) Valid() bool
type Transceiver ¶
type Transceiver interface {
io.ReadWriteCloser
Open() error
IsOpen() bool
Valid() bool
}
Transceiver abstracts a ReadWriteCloser and the functions expected by Bus for opening / closing streams.
Source Files
Directories