> For the complete documentation index, see [llms.txt](https://beyond-robotix.gitbook.io/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://beyond-robotix.gitbook.io/docs/heated-pitot/telemetry.md). # Telemetry The node publishes its status using the standard DroneCAN `uavcan.equipment.power.BatteryInfo` message, broadcast every heater cycle (\~200 ms, i.e. **5 Hz**) at medium transfer priority. This message is for information only and not required for operation. Publishing can be turned off entirely with the `TELEM_EN` parameter. > **We've adapted the battery message for our heated pitot purpose. The fields no longer reflect their original meanings. Doing this allows us to use a standard message, but does mean the fields require different interpretation to normal battery messages.** In particular, `state_of_health_pct` carries the **heater state**, and `state_of_charge_pct` carries the **output power in watts**. ### Field mapping | BatteryInfo field | Carries | Units / encoding | How to interpret | | --------------------- | ----------------------------------------- | ---------------------------- | ----------------------------------------------------------------- | | `temperature` | Heater (thermocouple) temperature | Kelvin | Subtract **273** to get °C. | | `voltage` | Heater output voltage (to heater element) | Volts | As-is. Measured directly on the board's ADC divider. | | `current` | Heater current (**inferred**) | Amps | Not measured. Computed as `voltage / R_HEATER` — see below. | | `state_of_health_pct` | **Heater state machine state** | Enum (0–9) see section below | Decode with the state table below. **Not** a health percentage. | | `state_of_charge_pct` | **Heater output power** | Watts | Integer watts (0…`P_MAX`). **Not** a charge percentage. | | `battery_id` | `DEVICE_ID` parameter | — | Identifies which node this is; set via the `DEVICE_ID` parameter. | All other `BatteryInfo` fields (remaining capacity, status flags, model name, etc.) are left at their defaults (zero/empty) and carry **no meaning** — do not read anything into them. #### `temperature` — °C conversion The firmware sends `heater_temperature + 273`, so: ``` heater_temp_°C = temperature_field − 273 ``` (Note it adds a flat 273, not 273.15, so expect up to \~0.15 °C of rounding offset versus a true Kelvin→Celsius conversion — negligible for monitoring.) #### `current` — inferred, not measured The node carries no current sensor. It samples the heater output voltage on its ADC divider and applies Ohm's law using the `R_HEATER` parameter (heater resistance in hundredths of an ohm, default `235` = 2.35 Ω, the measured element resistance): ``` current_A = voltage_V / (R_HEATER / 100) ``` Two consequences worth knowing before you trust the number: * **It is only as good as `R_HEATER`.** If the element in your probe isn't the nominal one, set the parameter to its measured cold resistance. * **It reads high when hot.** The element's resistance rises with temperature while `R_HEATER` is fixed, so real current at operating temperature is somewhat lower than reported. Use it for trend and sanity-checking (is the heater drawing roughly what the commanded power implies?), not for energy accounting. #### `state_of_health_pct` — heater state enum The heater state-machine state is cast directly to an integer and placed in this field. Decode it as: | Value | State | Meaning | | ----- | -------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | `0` | `INITIALISE` | Starting up / re-initialising: clearing buffers, configuring the PID controller. | | `1` | `OFF` | Heater commanded off (via actuator command). | | `2` | `FAULT` | Recoverable fault detected (bad thermocouple reading, implausible rate-of-change, or suspected thermal runaway). Will retry normal operation after `FAULT_S`. | | `3` | `HARD_FAULT` | Terminal fault — only a power cycle resets this. The node also flags itself CRITICAL/OFFLINE and blinks its LED rapidly. This will occur if any of the onboard sensor circuits cannot be found on start-up. Likely the board has been damaged, replace heater board. | | `4` | `FAIR_WEATHER` | Idle: warm enough that heating isn't needed yet (only when `EN_FAIRWEATHER` is enabled). | | `5` | `STANDBY` | Not entered. Retained so the enum numbering stays stable; a node in it is redirected to `CONTROL`. | | `6` | `STANDARD` | Not entered. As above. | | `7` | `UNPOWERED` | No heater supply on Vin. The node still runs off the bus rail, so it stays fully alive on CAN. | | `8` | `SELFTEST` | Hardware self-test running. `state_of_charge_pct` reads 0 throughout, even though the heater is being driven. | | `9` | `CONTROL` | Active closed-loop heating toward `T_TARGET`. | Normal warmed-up operation sits in **CONTROL (9)**. Seeing **FAULT (2)** or **HARD\_FAULT (3)** indicates a problem — most often a thermocouple that has come loose or a probe that has physically detached. **UNPOWERED (7)** means the heater supply is missing, not that the node has failed. #### `state_of_charge_pct` — output power (W) The heater's commanded output power (the PID demand, 0…`P_MAX` watts) is cast to an integer and placed here. So a value of `35` means the heater is currently being driven at \~35 W. It is **not** a percentage and does not map to 0–100. > Because this field is a `uint7` (0–127) in the standard message, and `P_MAX` maxes out at 70 W, the value comfortably fits. Read it as raw watts. ### Reading it in a ground station Most GCS software will display this as a "battery." To make sense of it: * **Temperature** — displayed in Kelvin by many tools; subtract 273 for °C. * **Voltage** — the heater output voltage (not a battery). * **Current** — an estimate, not a measurement; see the note above. * **State of Health** — ignore the "%" label; read the number against the **state table** above. * **State of Charge** — ignore the "%" label; read the number as **watts of heater power**. * **Battery ID** — matches the node's `DEVICE_ID` parameter, letting you tell multiple heated-pitot nodes apart. ### Worked example A received `BatteryInfo` of: ``` temperature = 333.0 (K) voltage = 13.6 (V) current = 5.8 (A, inferred) state_of_health_pct = 9 state_of_charge_pct = 35 battery_id = 0 ``` means: heater at **60 °C** (333 − 273), driven at **13.6 V** (≈ **5.8 A** inferred through a 2.35 Ω element), in the **CONTROL** state (active closed-loop heating), currently driving **35 W**, reported by the node whose `DEVICE_ID` is **0**.