CAN-FD Bridge Mode

Mode 4 · Pulsar only · Introduced in firmware v4.4.0

CAN-FD Bridge Mode turns the Pulsar’s virtual COM port into an SLCAN interface: ASCII commands, one per line, terminated with \r. It handles both classic CAN and CAN-FD, standard (11-bit) and extended (29-bit) IDs, with per-frame bit-rate switching.

It is interoperable with python-can’s slcan interface and with CANable-style terminal tools.

Danger

Not available on Binho Supernova. Selecting this mode on a Supernova is rejected with an invalid-parameter error.

Note

The COM port’s baud rate is irrelevant: this is a USB CDC endpoint, not a real UART. The CAN bus bitrate is set with the S and Y SLCAN commands, not by the serial port settings.

Quick start

{% stepper %} {% step %}

Switch the Pulsar into CAN-FD mode

python device_settings_cli.py --device pulsar set --cdc-mode canfd

The tool resets the device to apply the change. {% endstep %}

{% step %}

Drive it from python-can

import can

bus = can.Bus(interface="slcan", channel="COM7", bitrate=500000)

msg = can.Message(arbitration_id=0x123, data=[0xDE, 0xAD], is_extended_id=False)
bus.send(msg)

print(bus.recv(timeout=1.0))

The bitrate argument sets the nominal (arbitration) rate. The FD data phase defaults to 5 Mbps; call bus.set_bitrate(nominal, data) to choose another. {% endstep %} {% endstepper %}

SLCAN command set

Command	Meaning
S0–S8	Select the nominal (arbitration) bitrate
Y1 / Y2 / Y5	Select the CAN-FD data-phase bitrate
O	Open the channel
L	Open the channel listen-only (bus monitor; transmit disabled)
C	Close the channel
t / T	Transmit a classic frame, standard / extended ID
d / D	Transmit a CAN-FD frame without bit-rate switching
b / B	Transmit a CAN-FD frame with bit-rate switching
V / N / F	Version, serial number, status flags

Lowercase means a standard ID, uppercase an extended ID. Any unrecognized command returns \a.

Frame format

<cmd><ID><DLC><data...>

The ID is 3 hex digits for standard, 8 for extended. The DLC is one hex digit, followed by that many bytes as hex pairs. Received frames come back in the same shape, with the leading letter indicating what arrived.

For classic CAN, DLC 0–8 is the byte count. CAN-FD extends it:

DLC	Bytes	DLC	Bytes
9	12	D	32
A	16	E	48
B	20	F	64
C	24

Bitrates

Nominal rates: S0 10 kbps, S1 20 kbps, S2 50 kbps, S3 100 kbps, S4 125 kbps, S5 250 kbps, S6 500 kbps, S7 800 kbps, S8 1 Mbps.

Data-phase rates: Y1 1 Mbps, Y2 2 Mbps, Y5 5 Mbps. Only these three are offered, because they are the rates that are exact at the CAN core clock; other digits return \a.

Without S or Y, the channel opens at 500 kbps nominal and 5 Mbps data.

Caution

Bitrate commands are captured when the channel opens. Always send S and Y before O or L: changing them afterwards has no effect until the channel is closed and reopened.

Limitations

• No remote (RTR) frames: neither transmit nor receive.
• No receive timestamps.
• No error-frame or bus-state reporting to the host.
• No host-side acceptance filtering: every incoming ID is accepted, standard and extended alike. Filter in the application.
• V, N and F return fixed constants, not live device values.
• s (custom nominal bit timing) is accepted but does nothing. Use S.

Getting back out

python device_settings_cli.py --device pulsar set --cdc-mode uart_passthrough