phoenix-flight-computer

Flight computer firmware for Rocket Propulsion Lab's flagship liquid-propellant rocket Phoenix.

This system:

• Receives valve state commands from Phoenix Ground Station over raw Ethernet
• Actuates flow/pressurant/vent valves according to received commands.
• Samples pressure transducers (and other sensors in a modular fashion)
• Streams telemetry frames back to the ground over raw Ethernet.
• Is structured to allow easy/clean addition of new sensors and actuators as self-contained modules.

Repo Structure

phoenix-flight-computer/
├── phoenix-flight-computer.ino     # Main entry: setup(), loop(), Ethernet RX/TX, module orchestration
├── src/
│   ├── w5500/                      # MACRAW driver wrapper for Wiznet W5500
│   ├── valve/                      # Valve abstraction & state machine
│   └── pt/                         # Pressure transducer abstraction & configuration
├── docs/
│   └── diagrams/                   # Valve / plumbing / system diagrams
├── LICENSE
└── README.md

High Level Operation

On boot:

• Initialize serial for debugging (disabled for deployment).
• Initialize W5500 Ethernet Chip in MACRAW mode with according MAC address.
• Initialize all valves.
• Initialize all pressure transducers On loop:
• Read Ethernet frames and update valve target state.
• Apply valve target state to valves.
• Aggregate sensor readings and transmit telemetry frame to ground station.

Ethernet Communication Protocol

The Phoenix FC and ground station communicate using custom raw Ethernet frames over the W5500.

MAC Addressing

Each device is assigned a unique unicast MAC:

// Ground station
const uint8_t MAC_GROUND_STATION[6] = {0x02, 0x47, 0x53, 0x00, 0x00, 0x01}; // "GS"
// Relief valve controller (separate from main flight computer)
const uint8_t MAC_RELIEF_VALVE[6]   = {0x02, 0x52, 0x56, 0x00, 0x00, 0x02}; // "RV"
// Phoenix sensor/flight copmuter (this repo)
const uint8_t MAC_SENSOR_GIGA[6]    = {0x02, 0x53, 0x49, 0x00, 0x00, 0x04}; // "SI, Sensor Interface"

Frame Type

There are two custom EtherTypes:

• Command frames (GS to SI/RV): 0x63e4
• Telemetry frames (SI to GS): 0x8889

Generic Frame Layout

+------------+------------+-----------+-----------------+
| Dst MAC(6) | Src MAC(6) | Type (2)  | Payload (N ...) |
+------------+------------+-----------+-----------------+

Valve Command Frames (GS to SI)

EtherType: 0x63e4

Payload format:

The mapping from bits to physical valves is defined in src/valve/valve.h via named masks.

Telemetry Frames (SI to GS)

EtherType: 0x8889

Telemetry is currently serialized as simple CSV ASCII string in payload.

Payload format:

Payload: "PT0,PT1,...,PTn,LC1,LC2,LC3,TC1,TC2\r\n"

Where:

• PT[i] = engineering-value pressure in PSI
• LC[i] = load cell readings (currently set to 0 as placeholder)
• TC[i] = thermocouple readings (currently set to 0 as placeholder)

Valve System

Valve control is encapsulated in src/valve/. Conceptually:

• Physical valves are abstracted to single bit in state.
• Module is responsible for enforcing proper voltage to said valves.

Pressure Transducer System

Pressure transducers are encapsulated in src/pt/. Conceptually:

• Each PT has a unique engineering pressure range and output voltage range.
• The module holds static configurations of all PTs. To add/modify existing PTs, edit the configuration in src/pt/ and the main flight software loop automatically aggregates all readings.

Launch Control - Dev Mode (Risk: High)

• This mode is intended for testing valve openings before fueling
• All valves are free to be switched on and off
• Be very sure of what you are doing when using this mode

Launch Control - Fueling Mode (Risk: Medium)

• In fueling mode, all flow valves are locked in OFF mode
• all vent valves can be controlled by individual switch

Launch Control - Launch Mode (Risk: Low)

Buttons/Switches

• Abort (button): has highest priority, open vent valves for all
• Arm (switch): open/close pressurant valves
• Launch (button): open flow valves

Physical Specification

MCU

Arduino Mega 2560

Ethernet

W5500 Ethernet LAN Network Module