MQTT Protocol

Overview

Topics are organized into top-level commands and telemetry topics. Payloads are JSON.

Telemetry Topics

Telemetry topics are under the telemetry top-level topic, then by location on the vehicle, then by sensor type. e.g., telemetry/injector/temperature.

telemetry/chamber/pressure
telemetry/chamber/temperature
telemetry/supply/pressure
telemetry/tank/pressure
telemetry/tank/fuel/pressure
telemetry/tank/oxidizer/pressure
telemetry/tank/vent/temperature
telemetry/tank/weight/1
telemetry/tank/weight/2
telemetry/tank/weight/3
telemetry/tank/weight/4
telemetry/thrust
telemetry/voltage
telemetry/current

Telemetry Payload

{
  "timestamp": 1744708825844, // unix time in milliseconds
  "label": "PT-EI202", // P&ID label
  "value": 309.1, // floating-point number
  "unit": "psi"
}

Valve Position Telemetry Payload

{
  "timestamp": 1744708825844, // unix time in milliseconds
  "label": "SV-E203", // P&ID label
  "value": "open", // 'open', 'closed', or floating-point number indicating position in degrees
}

Commands

Command are send to the commands top-level topic.

Command Payload

{
  "command": <command>,
  "parameters": {<parameter key-value pairs}
}

Commands

ABORT

Initiates the abort sequence.

Parameters

None

IGNITE

Initiates pyrotechnic igniter

Parameters

None

TARE

Starts 5 second tare operation on all four load cells.

Parameters

None

VALVE

Commands valve to move to a specified position

Parameters

Key	Ex. Value	Description
valve	FV01	P&ID label for the valve to be commanded.
position	<open/close>	Commanded position for the value to move to.