CAN concepts

Controller Area Network (CAN) is the physical and data-link foundation for J1939 and many embedded labs in Embedded32.

Frame structure (classic CAN)

block-beta
  columns 8
  block:header:8
    SOF["SOF"]
    ID["11/29-bit ID"]
    RTR["RTR"]
    IDE["IDE"]
    DLC["DLC"]
    DATA["0–8 data bytes"]
    CRC["CRC"]
    ACK["ACK"]
    EOF["EOF"]
  end

Embedded32 works with logical frames in TypeScript:

interface CANFrame {
  id: number;
  data: number[]; // up to 8 bytes (classic CAN)
  extended?: boolean; // 29-bit ID when true
}

Identifier - standard vs extended

Type	ID bits	J1939 usage
Standard	11	Rare in heavy-duty J1939 labs
Extended	29	Required for J1939 on CAN

J1939 packs priority, PGN, and source address into the 29-bit extended ID. See J1939 concepts.

Driver abstraction

flowchart TB
  APP[Application / CANInterface]
  DRV{Driver}
  MOCK[MockCANDriver]
  VIRT[VirtualCANPort]
  SOCK[SocketCANDriver]
  APP --> DRV
  DRV --> MOCK
  DRV --> VIRT
  DRV --> SOCK

Driver	Hardware	Use case
`MockCANDriver`	None	Unit tests, examples
`VirtualCANPort`	None	In-memory bus between peers
`SocketCANDriver`	Linux SocketCAN	`vcan0`, real adapters

Send and receive flow

sequenceDiagram
  participant App
  participant IF as CANInterface
  participant Drv as Driver
  App->>IF: send(frame)
  IF->>Drv: write frame
  Drv-->>IF: incoming frame event
  IF-->>App: onMessage(callback)

Filtering

CANInterface supports acceptance filters so modules only receive relevant IDs - useful when simulating multiple ECUs on one bus.

Hardware-free learning path

Use MockCANDriver in examples/ and package examples.
Connect two virtual endpoints with VirtualCANPort for bus semantics.
Optionally move to vcan0 on Linux for SocketCAN labs.

Common student mistakes

Forgetting extended: true for J1939 frames
Treating id as decimal when docs use hex (0x18F00401)
Expecting CAN FD - Embedded32 classic CAN labs use 8-byte payloads