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title: CanKit.Pro.J1939Tp description: SAE J1939-21 transport protocol: TP.BAM and TP.CM

L3 · Transport SAE J1939-21 transport protocol: TP.BAM and TP.CM

CanKit.Pro.J1939Tp

SAE J1939-21 Transport Protocol (TP) for CanKit.Pro. Implements both flavors of the J1939-21 §5.10 transport service:

Status: 1.0.0 – 1.2.3 are withdrawn from nuget.org — they were published as stable before the API had been reviewed. 1.3.0 will be the first release whose API is stable; until it is tagged there is no listed version to install, so the dotnet add package line below resolves nothing and the withdrawn releases come back only on an exact version pin. The public surface can still change until then. See Versioning.

  • TP.BAM (Broadcast Announce Message) — one sender pushes an up-to-1785-byte PDU to every node on the bus, no acknowledgement (FR-TP-030).
  • TP.CM (Connection Mode: RTS / CTS / EndOfMsgAck / Connection Abort) — point-to-point, with block-size negotiation and end-of-message acknowledgement (FR-TP-031).

TP.DT (Data Transfer) frames carry the segmented payload for both flavors, sequence-numbered from 1 (FR-TP-032). Every session runs on its own actor-owned state and its own set of IDeadlines (T1, T2, T3, T4, Tr, Th — FR-TP-033), so multiple sessions can execute in parallel over the same physical bus (FR-TP-034/035) without interfering with each other.

The channel ships on nuget.org alongside the other CanKit.Pro.* L2/L3 building blocks. It re-uses:

  • CanKit.Pro.RawCan — one ICanBusService per channel to demultiplex the TP.CM / TP.DT frames back out of the shared bus stream and to confirm outbound frames.
  • CanKit.Pro.Actor — one IProtocolActor mailbox for single-writer session state.
  • CanKit.Pro.Reliability — IDeadlineScheduler for T1/T2/T3/T4/Tr/Th, cancelled/re-armed on the actor's loop.
  • CanKit.Pro.Addressing — J1939Id / J1939Pgn for composing the TP.CM (PGN 0xEC00) and TP.DT (PGN 0xEB00) 29-bit IDs.

Basic usage

using CanKit.Abstractions.API.Can;
using CanKit.Core;
using CanKit.Pro.J1939Tp;

// One bus, two nodes on their own source addresses.
using var bus = CanBus.Open("virtual://demo/0",
    cfg => cfg.SetProtocolMode(CanProtocolMode.Can20).Baud(500_000));

using var sender   = J1939Tp.Open(bus, sourceAddress: 0x01);
using var receiver = J1939Tp.Open(bus, sourceAddress: 0x02);

// TP.BAM: broadcast to every node.
await sender.SendBamAsync(pgn: 0xFECA, payload: new byte[100]);

// TP.CM: point-to-point with RTS/CTS/EOM.
await sender.SendCmAsync(pgn: 0xFECB, destinationAddress: 0x02, payload: new byte[300]);

var received = await receiver.ReceiveAsync();
// received.Pgn / received.SourceAddress / received.DestinationAddress / received.Payload

Coverage

Requirement Status
FR-TP-030 (TP.BAM send/receive) Yes
FR-TP-031 (TP.CM RTS/CTS/EndOfMsgAck) Yes
FR-TP-032 (TP.DT reassembly, SN 1..N) Yes
FR-TP-033 (T1/T2/T3/T4/Tr/Th via DeadlineScheduler, Connection Abort) Yes
FR-TP-034 (parallel sessions on shared bus) Yes
FR-TP-035 (multiple concurrent TP.CM peers) Yes

Install

dotnet add package CanKit.Pro.J1939Tp

# plus a CanKit adapter for the hardware you actually talk to, e.g.
dotnet add package CanKit.Adapter.Virtual   # loopback, no hardware

Dependencies: CanKit.Abstractions, CanKit.Pro.Actor, CanKit.Pro.Addressing, CanKit.Pro.RawCan, CanKit.Pro.Reliability.

Part of CanKit.Pro — higher CAN protocol layers built on top of CanKit, which is consumed as a NuGet package rather than forked.

License

MIT — see LICENSE. CanKit itself is a separate project licensed under Apache-2.0; see THIRD-PARTY-NOTICES.md.