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CANopen Viewer

The CANopen Viewer provides a live interface for interacting with instrumentation boards on the CAN bus. You can inspect node status, browse error histories, and manually read/write object dictionary entries via SDO operations — invaluable for debugging hardware communication during test development.

Hotkey: F7

Overview

The panel has two parts:

  1. Node List — shows all registered nodes with their NMT and heartbeat status.
  2. Node Explorer — opens when you click a node; provides tabs for errors and SDO operations.

Node List

The main panel displays a table of all CANopen nodes registered in the current environment:

Column Description
Name Board name (from Environment.Ib.Add())
Node ID CANopen node ID (hex)
State Heartbeat state and NMT state

Status Indicators

  • HB (Heartbeat): Active, Timeout, Unknown — whether the node is sending heartbeats.
  • NMT (Network Management): Operational, Pre-operational, Stopped, Initializing.

A node in Operational + Active state is healthy and ready for SDO communication.

Actions

  • Click a node row to open its Node Explorer tab.
  • "Restart" button — resets the entire CANopen stack (all nodes re-initialize).

Node Explorer

When you click a node, it opens in a tabbed explorer window with three tabs:

Active Errors

Shows currently active error conditions on the node. Each error displays:

  • Error status bit (kind)
  • Error code
  • Additional info bytes

Active errors indicate ongoing problems (e.g., overcurrent, communication failure). They clear when the condition resolves.

Error History

Shows the history of emergency messages received from the node. Each entry includes:

  • Timestamp of when the error occurred
  • Error code and additional information
  • Whether the error was set or cleared

This is useful for diagnosing intermittent issues that have already resolved by the time you look.

SDO (Upload / Download)

The SDO tab lets you manually read from and write to the node's object dictionary.

SDO Operations

Upload (Read)

Read a value from the node's object dictionary:

  1. Enter the Index (hex, e.g., 0x2001).
  2. Enter the Sub-Index (e.g., 0).
  3. Select the Data Type (bool, int8, uint16, float, double, string, etc.).
  4. Set Timeout in milliseconds (default: 1000).
  5. Click Upload.

The result appears in the request history below, showing either the read value or an error (abort code).

Download (Write)

Write a value to the node's object dictionary:

  1. Enter the Index and Sub-Index.
  2. Select the Data Type.
  3. Enter the Value to write.
  4. Set Timeout.
  5. Click Download.

The result (success or abort code) appears in the request history.

Request History

Both upload and download tabs maintain a scrollable history of all requests made during the session:

Column Description
Index The OD index requested
Sub-Index The sub-index
Result The read value (upload) or success/failure (download)
Abort Code If failed, the CANopen abort code explaining why

Failed requests are highlighted in red. In-progress requests are highlighted in yellow.

Options

Option Default Description
Timeout 1000 ms How long to wait for a response
Retries 5 Number of retry attempts on failure
Block transfer Off Use block SDO transfer (for large data)
Hex input Off Interpret the download value as hexadecimal

Error Generator

Advanced / Dangerous

The Error Generator is a developer tool for simulating error conditions on the CANopen stack. It can trigger emergency messages and error states. Do not use this unless you understand the implications.

Access via the "Error Generator" button in the main panel. It allows you to inject specific error kinds and codes into the CANopen stack for testing error handling logic.

Common Use Cases

Verifying Board Communication

  1. Open CANopen Viewer (F7).
  2. Check that your boards show HB: Active, NMT: Operational.
  3. Click a node → SDO tab → upload a known entry (e.g., "Device Name" at index 0x1008).
  4. Verify the returned value matches expectations.

Debugging a Failed SDO in Test Scripts

If a test fails with an SDO timeout or abort:

  1. Open the CANopen Viewer.
  2. Manually upload the same index/sub-index.
  3. Check the abort code — common codes:
  4. 0x06020000 — object does not exist
  5. 0x06010001 — attempt to read a write-only object
  6. 0x06010002 — attempt to write a read-only object
  7. 0x08000020 — data transfer timeout
  8. 0x06090011 — sub-index does not exist

Manually Commanding Hardware

During development, you can manually download values to control hardware without writing test scripts:

  1. Open a node → SDO → Download tab.
  2. Write to the desired OD entry (e.g., set a DAC output, toggle a relay).
  3. Observe the hardware response.

Tips

  • Check heartbeat first. If HB shows Timeout, the node is not responding — check power, CAN wiring, and baud rate before trying SDO operations.
  • Use the correct data type. SDO operations are type-sensitive. Reading a REAL32 entry as uint32 will give you the raw IEEE 754 bits, not the float value.
  • Keep the panel open during test development. The error history captures emergencies in real-time, which helps correlate hardware errors with test failures.
  • Restart after bus errors. If the CAN bus enters error-passive or bus-off state (visible in the Device Viewer LED indicators), use the "Restart" button to recover.

See Also