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Protocol Stack & Application Decoders

CAN & CANopen Studio features an extensible application decoder architecture.

Supported Decoder Profiles

1. Generic CANopen (CiA 301 / CiA 402)

  • CiA 301 (Base Communications):
  • Network Management (NMT, COB-ID 0x000)
  • Synchronization (SYNC, COB-ID 0x080)
  • Emergency frames (EMCY, COB-ID 0x081..0x0FF)
  • Heartbeat & Boot-up (COB-ID 0x701..0x77F)
  • SDO Request (0x600 + NodeID) and SDO Response (0x580 + NodeID)
  • CiA 402 (Drives & Motion Control):
  • Statusword (0x6041) bitfield decoding: Not Ready to Switch On, Switch On Disabled, Ready to Switch On, Switched On, Operation Enabled, Quick Stop, Fault
  • Controlword (0x6040) bitfield decoding
  • Target & Actual Velocity (0x606C) in RPM

2. SEVCON Gen4 AC/PMSM Inverter

  • TPDO1 (0x148): Inverter status vectors (v1 to v4)
  • TPDO2 (0x441): Motor status monitor (m1 to m4)
  • TPDO3 (0x156): Heatsink temperature (°C), raw motor temperature, auxiliary voltage
  • TPDO4 (0x270): Control mode, speed limit steps, target torque (0x6071)
  • TPDO5 (0x473): Actual motor speed (0x606C) and maximum speed (0x6080) in RPM

3. De Haardt Track Safety Transponder

  • Speed mode decoding:
  • 0: Emergency Stop (Red Flag)
  • 1: Pit Lane Speed (Very Slow)
  • 2: Slow Speed (Yellow Flag)
  • 3: Normal Speed (Green Flag)
  • 4: Boost / Fast Mode

4. J1939 Extended (29-bit)

  • Extracts Priority (3 bits), Parameter Group Number (PGN, 18 bits), Source Address (8 bits), and Destination Address.

Creating a Custom Decoder

To create a new decoder, simply create a class inheriting from BaseDeviceDecoder decorated with @register_decoder:

from canopen_stack import BaseDeviceDecoder, CanopenMessage, register_decoder


@register_decoder
class MyCustomBmsDecoder(BaseDeviceDecoder):
    @property
    def device_name(self) -> str:
        return "Custom BMS Battery Monitor"

    @property
    def custom_cob_ids(self):
        return {
            0x190: "BMS Status & Voltage",
            0x290: "BMS Cell Temperatures",
        }

    def can_decode(self, message: CanopenMessage) -> bool:
        return message.arbitration_id in (0x190, 0x290)

    def decode(self, message: CanopenMessage):
        cid = message.arbitration_id
        data = message.data
        signals = {}

        if cid == 0x190 and len(data) >= 4:
            voltage = int.from_bytes(data[0:2], "little") * 0.1
            current = int.from_bytes(data[2:4], "little", signed=True) * 0.1
            signals["pack_voltage_v"] = voltage
            signals["pack_current_a"] = current
            message.decoded_info = f"BMS -> Voltage: {voltage:.1f}V | Current: {current:.1f}A"

        return signals
The application will automatically discover, load, and display your decoder in the user interface!