CANopen

CANopen

CANopen is an industrial fieldbus protocol that runs on a standard CAN network. Use it when you need to exchange cyclic process data with drives, I/O modules, sensors, or other CANopen devices — for example fan controllers, valve drivers, or third-party modules that speak CANopen PDOs rather than a custom CAN message list.

Overview

For each CAN bus you can:

1. Turn CANopen on and optionally act as network master (NMT).
2. Optionally produce SYNC and heartbeat.
3. Define nodes (devices on the bus by node address).
4. On each node, define PDOs (process data objects) that either transmit (encode channels onto the bus) or receive (decode bus data into channels).
5. Export / import the whole CANopen configuration for that bus as a .canopen file.

Where to find it

1. Open Communications.
2. Select the CAN bus you want to configure.
3. On Settings, enable CANopen.
4. Open the CANOpen tab (shown when CANopen is enabled).

Bus settings (Settings tab)

These appear under the CANOpen heading on the bus Settings tab (alongside name, bit rate, and termination).

CAN bus basics (still required)

CANopen uses the same CAN bus settings as other traffic:

• Bit rate — Must match all devices (commonly 250 kbit/s, 500 kbit/s, or 1 Mbit/s).
• Termination — Enable bus termination only when this device is at a physical end of the bus (120 Ω).

CANopen tab

With CANopen enabled, the CANOpen tab configures nodes and PDOs for that bus.

Export and import

At the top of the tab:

Nodes

A node is one CANopen device on the bus, identified by its node address (node-ID).

Node list

• Lists all configured nodes.
• Labels show address and enabled state, e.g. Node 3 [On].
• Drag to reorder (order is for organisation only; the bus address is what matters).
• Add Node creates a node with the next free address (1–127) and Enabled on.

Node settings

PDOs (process data objects)

PDOs are the cyclic data packets of CANopen. Each PDO belongs to a node and has a direction:

Adding PDOs

• Add TX PDO — Creates a transmit PDO with COB base 0x200 (standard RPDO1 base when you are the master writing to a slave).
• Add RX PDO — Creates a receive PDO with COB base 0x180 (standard TPDO1 base for data from a slave).

These defaults match the common predefined connection set; change the COB base if your device datasheet specifies different IDs.

PDO settings

Transmit types

Effective CAN ID

Displayed for the selected PDO:

Effective CAN ID = COB Base + (Node Address & 0x7F)

Example:

Encode (transmit mapping)

For a TX PDO, encode entries pack channel values into the 8-byte payload.

Encode list

• One row per field in the frame.
• Label shows channel name and byte index (or “(no channel)” if unassigned).
• Add Encode appends a field; the next free byte index is suggested automatically when possible.

Encode settings

How encoding works (simple model)

raw = round(channel_value × multiplier)
raw = (raw & mask) << left_shift
store raw in payload at byte_index for byte_count bytes (little-endian)

Multiple encode fields can share a byte (values are ORed into the payload), which is useful for bit-packed flags.

Decode (receive mapping)

For an RX PDO, decode entries unpack the payload into channels.

Decode list

Same idea as encode: list of fields with channel + byte position.

Decode settings

How decoding works (simple model)

raw = read little-endian integer at byte_index for byte_count
raw = (raw >> right_shift) & mask
if signed: sign-extend using mask width
channel_value = raw / multiplier

Typical setup workflow

Command a slave (master → device)

1. Enable CANopen on the correct bus; set bit rate and termination as needed.
2. Turn on Act as Network Manager if this unit should start the network.
3. Add Node with the device’s node address; keep Enabled on.
4. Add TX PDO (default base 0x200 is often correct for RPDO1).
5. Add encode fields for enable, setpoint, etc., matching the device manual (byte layout, scaling).
6. Optionally Add RX PDO (base 0x180 for TPDO1) and decode status feedback into channels.
7. Optionally set heartbeat consumer on the node if the device produces heartbeats.
8. Apply/send configuration and watch CANopen Tx/Rx Count channels and live channel values.

Example: 16-bit scaled speed at bytes 2–3

Device expects target speed × 10 as unsigned 16-bit little-endian at bytes 2–3:

Status channels

Per CAN bus index (1–4), the firmware publishes counters you can log or display:

If TX count stays at zero: confirm CANopen Enable, node Enabled, PDO is Transmit, configuration has been applied to the device, and the CAN bus is online.

Quick reference — COB-ID bases (predefined set)

These are industry-standard bases; many devices use them by default:

Always confirm against the device manual — some products use custom COB-IDs.

Troubleshooting

Related

• Channels and Events — how channels are used across the system
• OBD-II — diagnostics protocol on CAN (different from CANopen)
• LIN Bus — another serial bus configuration page