Glossary¶

Short definitions for terms that show up in Radish docs, decoder output, and the ClimateTalk / CT-485 specs. For full protocol detail, see the specification archive.

A–C¶

A/B (Data 1 / Data 2)
The two-wire differential RS-485 pair used by CT-485. Equipment often labels these Data 1 / Data 2. If following the spec, they may be colored green / yellow. Reversed polarity produces inverted/noisy hex (FE/FF-heavy); swap the wires. See Wire and Verify.

Address Confirmation
Coordinator messages that push or confirm the network node list (who is on the bus and at which node types). Subordinates answer with a matching response. Missing or mismatched confirmations drive AutoNet keepalive / relinquish behavior.

App query
A read-only CT-CIM poll Radish originates after AutoNet join: Get Configuration (0x01), Get Status (0x02), Get Sensor Data (0x07), or Get Identification Data (0x0E). Triggered from Home Assistant via get_app_query; matching response hex is published on app_query_mqtt_topic. See Requesting application queries.

Air Handler
Indoor blower / coil equipment (node type 3 in CT-485). Often co-located with the network coordinator function on Daikin / ComfortNet systems.

AtomS3 Lite
M5Stack ESP32-S3 board used by the stock radish.yaml / radish2.yaml profiles.

AutoNet
ClimateTalk mechanism for a device to join the network as a subordinate: discovery → set-address → keepalive. Radish implements an AutoNet client in the ESPHome component (radish2.yaml). Keep it off until passive sniffing is solid. See ESPHome Component.

ClimateTalk
OEM communicating HVAC protocol family (Daikin / Amana / Goodman / related ComfortNet-style systems). Specs cover application messages (often called CT-CIM) and the CT-485 network/physical layers.

ComfortNet
Marketing name for many ClimateTalk-based residential communicating systems (thermostat + air handler / outdoor unit on a data bus).

Coordinator (Network Coordinator)
Device that runs the CT-485 network (address 255, node type 165): discovery, addressing, token / dataflow, and node-list pushes. Usually the air handler / control board, not Radish.

CT-485
ClimateTalk’s RS-485 network and framing layer: addresses, subnets, send methods, message types, checksums. This is what Radish sniffs on the wire and publishes as hex.

CT-CIM
ClimateTalk application / information-model messages carried inside CT-485 frames (status, sensors, menus, control, and so on).

D–M¶

Dataflow
Bus arbitration so a subordinate can transmit: typically R2R and Token Offer. Packets with packet-number bit 7 set are often ACKs / dataflow traffic; the Python listener can hide them with MQTT_EXCLUDE_DATAFLOW.

DE/RE
Driver Enable / Receiver Enable pins on many RS-485 chips. Some modules (including Tail485) handle direction automatically; breakout boards may need GPIO control in YAML.

DI / RO
Transceiver pins: DI = driver input (ESP TX → DI), RO = receiver output (ESP RX ← RO).

ESPHome
Firmware framework Radish uses on the ESP32. Profiles live in radish.yaml (sniff) and radish2.yaml (component + optional AutoNet).

Frame
One CT-485 packet: addressing header, message type, payload, checksum. Parsed by radish/frame.py and the on-device codec.

Heat Pump
Outdoor / heat-pump equipment (node type 5).

MDI
Message Data Item — structured records inside some CT-CIM payloads (for example status records with db_id, length, and value).

MQTT
Publish/subscribe messaging. Radish publishes raw hex on radish/rs485/raw (by default); mqtt_listener.py subscribes and decodes.

N–R¶

Node Discovery
Coordinator broadcast asking devices to announce themselves (message type 0x79 and related). First step of AutoNet join.

Node type
Numeric identity for the kind of device (thermostat 1, air handler 3, heat pump 5, temperature sensor 39, network coordinator 165, …). See radish/maps.py.

OTA
Over-the-air firmware update via ESPHome after the first USB flash.

Packet number
CT-485 header field distinguishing requests/responses and dataflow/ACK styles. Bit 7 set usually marks dataflow-related packets.

Polarity
Which physical wire is A vs B (Data 1 vs Data 2). Wrong polarity garbles UART bytes; correct by swapping the data pair.

R/C
Thermostat power rails: R (24 VAC hot) and C (common). Radish only needs the data pair for sniffing; do not tie RS-485 A/B to R/C.

R2R (Request to Receive / Ready to Receive)
Dataflow handshake message that helps a subordinate get a turn to send. The ESPHome component can answer when participating.

radish.yaml
Passive sniffing profile: uart.debug RX → MQTT hex. Does not join the network.

radish2.yaml
Profile that loads the local radish ESPHome component: on-device framing, dataflow replies, optional AutoNet, and originated app queries (configuration / status / sensor / identification).

Relinquish
AutoNet client drops its assigned address/subnet (for example after keepalive failure or AutoNet turned off) and waits to be rediscovered.

RS-485
Differential serial bus standard. CT-485 runs on RS-485 at 9600 baud in the stock configs.

S–Z¶

Send method
How a frame is addressed/routed (non-routed, by priority node type, by socket, …). Shown in decoder output.

Session ID
Identifier used with the ClimateTalk MAC during discovery / addressing so Set Address applies to the right device.

Set Address
Coordinator message that assigns a subordinate its network address and subnet during AutoNet.

Slot Delay
Randomized wait (100–2500 ms per CT-485, or a fixed YAML override) before answering Node Discovery so multiple devices do not collide.

Sniffing
Listen-only capture of bus traffic (no AutoNet join, no intentional TX beyond what the transceiver path allows for RX).

Subnet
CT-485 grouping: 0 = all, 2 = v1.0 subordinates, 3 = >v1.0 subordinates (common on modern gear).

Subordinate
Any addressed device that is not the coordinator (thermostat, heat pump, sensor, …). AutoNet joins Radish as a subordinate.

Tail485
M5Stack RS-485 “tail” that plugs onto the Atom. Stock YAML maps UART RX = GPIO1, TX = GPIO2.

Thermostat
User interface / zone controller (node type 1). Often priority subordinate address 1.

Token Offer
Coordinator dataflow offer allowing a filtered node to transmit. Paired with Token Offer Response from subordinates.

UART
Serial link between the ESP32 and the RS-485 transceiver. Stock baud rate is 9600 8N1.