python-can-candle 1.2.4

CAN driver for Geschwister Schneider USB/CAN devices

python-can-candle

Full featured CAN driver for Geschwister Schneider USB/CAN devices.

Support Multichannel and CAN FD.

Installation

pip install python-can-candle

Example

Using with python-can

This library implements the plugin interface in python-can, aiming to replace the gs_usb interface within it.

import can
from candle import CandleBus

# Create a CandleBus instance in the python-can API.
with can.Bus(interface='candle', channel=0, ignore_config=True) as bus:
    # Bus is an instance of CandleBus.
    assert isinstance(bus, CandleBus)

Set ignore_config=True is recommended to prevent potential type casts.

Configurations

You can configure the device by appending the following parameters when creating the can.Bus.

• bitrate: int, defaults to 1000000
• sample_point: float, defaults to 87.5
• data_bitrate: int, defaults to 5000000
• data_sample_point: float, defaults to 87.5
• fd: bool, defaults to False
• loop_back: bool, defaults to False
• listen_only: bool, defaults to False
• triple_sample: bool, defaults to False
• one_shot: bool, defaults to False
• bit_error_reporting: bool, defaults to False
• termination: bool or None, defaults to None

For example, create a canfd device with 1M bitrate and 5M data bitrate.

with can.Bus(interface='candle', channel=0, fd=True, bitrate=1000000, data_bitrate=5000000, ignore_config=True) as bus:
    ...

Connect multiple devices

When connecting multiple devices at the same time, you can set channel to serial_number:channel to create the specified can.Bus.

with can.Bus(interface='candle', channel='208233AD5003:0', ignore_config=True) as bus:
    ...

You can also select devices by appending some additional parameters.

• vid: int, vendor ID
• pid: int, product ID
• manufacture: str, manufacture string
• product: str, product string
• serial_number: str, serial number

Device Discovery

Detect all available channels.

channels = can.detect_available_configs('candle')
print(channels)

Open multiple channels of a single device

This driver now supports opening multiple channels from the same device in a single CandleBus instance.

• Pass a list of channel indices belonging to the same device, e.g. channel=[0, 1].
• For multiple devices, pass serial_number=SERIAL to select the device by serial number.
• Configure each channel separately with channel_configs.

Create a CandleBus instance with multiple channels.

bus = CandleBus(channel=[0, 1], serial_number='208233AD5003', bitrate=1000000)

Create and configure channels with different bitrates.

bus = CandleBus(channel=[0, 1], serial_number='208233AD5003', channel_configs={0: {'bitrate': 500000}, 1: {'bitrate': 1000000})

Send to a specific channel.

msg = can.Message(arbitration_id=0x100, channel=1, data=[0x1, 0x2, 0x3, 0x4])
bus.send(msg)

Send to multiple channels.

msg = can.Message(arbitration_id=0x100, channel=[0, 1], data=[0x1, 0x2, 0x3, 0x4])
bus.send(msg)

Distinguish channels in received messages.

msg = bus.recv()
print(f'Received message on channel {msg.channel}.')

Notes on multi-channel behavior

• send() routes frames to the target channel based on msg.channel (int, "SERIAL:idx", or Sequence[int]).
• recv() returns Message.channel set to the source channel number.
• When msg.channel is not set, send() defaults to the first channel.

Performance

The communication layer is implemented based on pybind11 with libusb. You can run the following scripts to evaluate the performance.

For single-channel performance:

python -m candle.stress

For multi-channel performance:

python -m candle.stress_multichannel

Reference

• linux gs_usb driver
• python gs_usb driver
• candleLight firmware
• candle_api