Architecture

MavNet is intentionally small. Each layer depends only on layers below it.

MavNet.Core
MavNet.Protocol
MavNet.Protocol.Generated
MavNet.Transport.Udp
MavNet.PX4
MavNet.Probe

Layers

  • MavNet.Core: shared primitives such as MavId, StateRate, and StateSubscription.
  • MavNet.Protocol: MAVLink v2 frame decode/encode primitives, X.25 CRC, message contracts, and the generated message registry.
  • MavNet.Protocol.Generated: generated message structs, enums, and command structs.
  • MavNet.Transport.Udp: one UDP socket, one receive loop, typed message events, and outbound GCS heartbeat.
  • MavNet.PX4: vehicle-level state and command helpers. Drone is the current high-level entry point.
  • MavNet.Probe: console sample for SITL/manual smoke testing.

Frame Rules

MavlinkFrame.TryDecode accepts MAVLink v2 frames only. It drops frames with:

  • MAVLink v1 magic
  • signed frames
  • unknown incompatibility bits
  • unknown message ids
  • payload lengths outside the generated min/max bounds
  • CRC mismatch
Important

Unknown incompatibility bits are dropped on purpose. MAVLink requires this for forward compatibility; accepting them can make future frames unsafe to forward or decode.

Generated Code

Do not hand-edit generated files:

  • src/MavNet.Protocol.Generated/
  • src/MavNet.Protocol/Generated/MessageRegistry.cs

Regenerate with:

dotnet run --project tools/MavNet.CodeGen

Adding a message means:

  1. Add it to tools/MavNet.CodeGen/allowlist.txt.
  2. Regenerate.
  3. Add a typed event and dispatch case in MavlinkConnection.
  4. Surface it in Vehicle / Drone only if it belongs in the high-level API.

Runtime Model

  • Receive events fire synchronously on the UDP receive thread.
  • Subscriber exceptions are swallowed so one bad handler does not kill the receive loop.
  • Send<T> uses generated static message metadata and strips MAVLink v2 trailing zero payload bytes.
  • Vehicle correlates COMMAND_LONG with COMMAND_ACK; some commands also wait for a confirming heartbeat state change.

Keep event handlers short. UI apps should dispatch from handlers into their UI synchronization context.

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