CANopen Driver

Overview

CANopen — the EN 50325-4 / CiA 301 standard application layer on top of the CAN bus (common in motor drives / encoders / IO modules). Rewritten natively in 2026-07 — the old delegation to Apache PLC4j canopen has been removed (PLC4X CANopen only supports the local SocketCAN transport and cannot be carried over TCP, so connect died on edges without a physical CAN bus). It now uses the in-house SDO expedited upload implementation in plantpulse-plc-protocol (CanopenSdoClient) plus a transport abstraction (CanTransport) — the same native pattern as AB-ETH / BACnet.

Item	Value
`opc_type`	`CANOPEN`
Implementation class	`plantpulse.driver.protocol.canopen.CANOpenDriver`
Library	In-house native (`canopen` in `plantpulse-plc-protocol` — SDO expedited upload)
Inheritance	`BaseProtocolDriver` (not PLC4j)
`getProtocol()`	`"canopen:tcp"` (retains the old PLC4X scheme notation — log/diagnostics compatibility)
Default port	`20200` (CAN-over-TCP gateway)
Status	Stable (SDO expedited polling)
read	OK (SDO expedited upload, values ≤ 4 bytes)
write	❌ (read-only — SDO download not implemented)
Security	None

CAN-over-TCP gateway prerequisite

The default transport (tcp) communicates with CANopen nodes located beyond a CAN ↔ TCP gateway. CAN frames are carried over TCP using canId(4B BE) + dlc(1B) + data[dlc]'s own binary framing (no handshake / bus name negotiation — identical framing to the simulator). transport=socketcan (local can0) is currently a stub (requires AF_CAN native bindings / JNI), so connect fails — the physical CAN interface track is planned as follow-up.

Class structure

BaseProtocolDriver
   └── CANOpenDriver — connect() 에서 CanTransport(tcp/socketcan) + CanopenSdoClient 생성

A read failure (Abort / timeout / socket) invalidates the socket (connected=false + close) so that the Edge is prompted to reconnect.

Wire format summary (in-house implementation — SDO expedited upload)

Request: COB-ID 0x600+nodeId, data [0x40, index LE(2B), subindex, 0×4].
Response: COB-ID 0x580+nodeId, command 0x43 (4B) / 0x47 (3B) / 0x4B (2B) / 0x4F (1B) — value little-endian. 0x80 = Abort (code u32 LE) → communication exception.
Segmented / block transfer not supported (values > 4B, e.g. long strings) — expedited is sufficient for scalar tag polling.

OPC registration options

Field	Meaning	Default
`opc_agent_ip`	CAN-TCP gateway IP	`192.168.1.20`
`opc_agent_port`	Gateway TCP port	`20200`
`options.read-timeout`	SDO response timeout (ms)	`3000`
`options.transport`	`tcp` / `socketcan` (stub)	`tcp`
`options.can-interface`	Interface name in socketcan mode	`can0`

Old PLC4X options removed

The node-id option from old forms/documents is deprecated — the node ID is now the first field of the tag address (see below). The request-timeout / heartbeat options are also not accepted by the native driver (the timeout is read-timeout).

Tag `plc_address` format (new contract)

<nodeId>:<index>:<subindex>[:<TYPE>]

Field	Meaning	Notation
`nodeId`	CANopen node id (1..127)	Decimal
`index`	Object dictionary index (0..0xFFFF)	`0x`-prefixed hex (`0x6041`) or decimal
`subindex`	Sub index (0..255)	`0x`-prefixed hex or decimal
`TYPE` (optional)	LE byte interpretation type	If omitted, inferred from `data_type` → if that is also absent, `UINT16`

Notation	Meaning
`1:0x6041:0:UINT16`	Node 1, DS402 Statusword
`3:0x2000:0:REAL`	Node 3, manufacturer area float32
`1:0x6064:0:INT32`	Position actual value (32-bit signed)
`5:8192:1`	Node 5, index decimal 8192 (= 0x2000), TYPE omitted → UINT16

TYPE tokens (aliases accepted)

Token (alias)	Size	Interpretation
`BOOL` (`BOOLEAN`)	1	true unless 0
`UINT8` (`U8`, `USINT`, `BYTE`) / `INT8` (`I8`, `SINT`)	1	u8 / i8
`UINT16` (`U16`, `UINT`, `WORD`) / `INT16` (`I16`, `INT`)	2	u16 / i16 (default UINT16)
`UINT32` (`U32`, `UDINT`, `DWORD`) / `INT32` (`I32`, `DINT`)	4	u32 / i32
`REAL` (`FLOAT`, `F32`, `REAL32`)	4	IEEE-754 float (LE)
`STRING` (`STR`, `VISIBLE_STRING`)	≤4	ASCII (trailing NUL stripped)

When TYPE is omitted, it is inferred from data_type: Boolean→BOOL, Integer→INT16, Long→INT32, Float→REAL, Double→REAL (4B approximation), String→STRING.

Supported / unsupported

read: SDO expedited upload (≤ 4 bytes) — OK.
write: unsupported — isWriteSupported() = false and write() always return false. (SDO download is a follow-up.)
Segmented / block SDO, PDO mapping, NMT / Heartbeat monitoring, SYNC, EMCY, LSS: unsupported.
Direct SocketCAN / USB-CAN: stub (CAN-over-TCP gateway assumed).

curl registration example

curl -X POST http://<edge-host>/api/v1/opc \
  -H "Content-Type: application/json" \
  -d '{
    "opc_id": "OPC_CANOPEN_DRIVE1",
    "opc_type": "CANOPEN",
    "opc_name": "Servo Drive 1",
    "opc_agent_ip": "192.168.1.20",
    "opc_agent_port": "20200",
    "site_id": "SITE_00001",
    "auto_collect": true,
    "timecycle": 1000,
    "options": { "read-timeout": "3000" },
    "tag_list": [
      {"tag_id":"OPC_CANOPEN_DRIVE1_T01","tag_name":"Statusword","plc_address":"1:0x6041:0:UINT16","data_type":"Integer"},
      {"tag_id":"OPC_CANOPEN_DRIVE1_T02","tag_name":"ActualPos","plc_address":"1:0x6064:0:INT32","data_type":"Long"}
    ]
  }'

References

CiA 301 (Application Layer) / CiA 402 (Drives) standards.
Code: plantpulse-edge-driver/src/plantpulse/driver/protocol/canopen/CANOpenDriver.java + the canopen package in plantpulse-plc-protocol.
Operations: the gateway framing is a proprietary binary format (canId+dlc+data) — different from the socketcand text protocol. Addresses should be validated against the device EDS file.

Overview​

Class structure​

Wire format summary (in-house implementation — SDO expedited upload)​

OPC registration options​

Tag plc_address format (new contract)​

TYPE tokens (aliases accepted)​

Supported / unsupported​

curl registration example​

References​