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Device Viewer

The Device Viewer manages the connection to SLCAN USB-to-CAN adapters and displays live CAN bus traffic. It shows which devices are connected, allows manual port selection, and provides a real-time view of CAN frames on the network.

Hotkey: F3

Overview

The Device Viewer serves two purposes:

  1. Connection management — detecting, connecting, and disconnecting SLCAN adapters.
  2. Network monitoring — showing live CAN frames with their IDs, data length, and payload.

Connection Status

The connection state is always visible in the main menu bar (top-right area):

  • Green text: "Connected (N)" — N SLCAN devices are connected and active.
  • Red text: "Disconnected" — no SLCAN devices are open.
  • LED indicators — red and green dots reflect the CANopen stack's state (TX/RX activity).

Click the connection status text to open the Device Viewer panel.

Connecting to a Device

Automatic Detection

On startup, Frasy scans all USB serial ports and automatically connects to devices matching the USB whitelist in config.json:

"communication": {
    "usbWhitelist": [
        { "vid": 1155, "pid": 42180, "mi": 0 }
    ]
}

SMarTest devices (DAQ, PIO, R8L) are always accepted regardless of the whitelist.

Hot-Plug Support

When a USB device matching the whitelist is connected or disconnected, the Device Viewer detects the change automatically and connects/disconnects as appropriate.

Manual Connection

If automatic detection doesn't work:

  1. Open the Device Viewer (F3).
  2. Select the serial port from the Port dropdown.
  3. Click Refresh if the port doesn't appear.

Network State

Once connected, the panel displays a live table of CAN frames seen on the bus:

Column Description
Id CAN frame ID (hex)
IsExt Whether this is an extended (29-bit) frame
IsRTR Whether this is a Remote Transmission Request frame
DLC Data Length Code (number of data bytes)
Data Raw data bytes (hex)

The table shows the last seen frame for each unique CAN ID. It updates in real-time as packets flow.

Statistics

Above the table, a status line shows:

  • Addresses — number of unique CAN IDs seen
  • Pending packets — packets queued for processing
  • Total packets — total RX packet count since startup
  • Packets/second — current receive throughput
  • kB/s — current bandwidth usage

Click Clear to reset the network state table and counters.

The Device Viewer contributes network usage indicators to the main menu bar:

  • RX/TX progress bars — color-coded from green (low usage) through yellow to red (high usage), showing CAN bus utilization.
  • LED dots — reflect the CANopen stack's internal red/green LED state (similar to physical CANopen device LEDs indicating NMT state and errors).

Configuration

The Device Viewer uses the communication key in config.json:

"communication": {
    "usbWhitelist": [
        { "vid": 1155, "pid": 42180, "mi": 0 }
    ]
}
Field Type Description
usbWhitelist array USB device identifiers to match for auto-connection
usbWhitelist[].vid int USB Vendor ID
usbWhitelist[].pid int USB Product ID
usbWhitelist[].mi int? USB Interface Number (optional)
usbWhitelist[].rev int? USB Revision (optional)

To find your adapter's VID/PID, check Windows Device Manager → the device's Properties → Details → Hardware Ids. The format is USB\VID_XXXX&PID_XXXX&MI_XX.

Tips

  • If the device isn't detected, verify the VID/PID/MI in Device Manager matches your whitelist entry in config.json.
  • "Pending packets" growing indicates the CANopen stack can't process frames fast enough. This may happen if many nodes are transmitting simultaneously.
  • Use this panel for hardware debugging. The raw CAN frame view helps identify communication issues (missing nodes, unexpected frames, wrong baud rate).
  • The panel can remain closed during normal operation. The connection is maintained regardless of panel visibility — the panel is just a monitoring tool.

See Also