USB CDC Operating Modes

The USB CDC interface (the virtual COM port the device presents alongside its USB HID interface) can do one of five different jobs. Which one it does is controlled by a single persistent device setting, stored in flash.

The modes are mutually exclusive: exactly one is active at a time.

Caution

Changing the mode writes the setting to flash, but the device keeps running in its current mode until it resets. The choice is made once, at boot.

The five modes

UART Passthrough→

Mode 0, the default, on both boards. The COM port is a transparent bridge to the device’s UART pins.

Terminal Mode→

Mode 1, Supernova only. The COM port becomes an interactive shell for driving I2C, I3C and GPIO by typing commands.

Nova Compatible Mode→

Mode 2, on both boards. The COM port speaks the legacy Binho Nova ASCII protocol, so existing Nova host software works unmodified.

RS-485 Bridge Mode→

Mode 3, Pulsar only. The COM port becomes a transparent half-duplex RS-485 bridge.

CAN-FD Bridge Mode→

Mode 4, Pulsar only. The COM port speaks SLCAN, so python-can and CANable tooling can drive the CAN bus.

Availability by device

Mode	Value	Supernova	Pulsar
UART Passthrough	0	Yes	Yes
Terminal	1	Yes	No
Nova Compatible	2	Yes	Yes
RS-485 Bridge	3	No	Yes
CAN-FD Bridge	4	No	Yes

Selecting a mode the device doesn’t support is rejected outright, so a device can’t be stranded in an unusable configuration this way.

Switching modes with device_settings_cli.py

device_settings_cli.py is a small host-side tool that reads and changes these settings over USB HID. It is the recommended way to switch modes: no Mission Control and no SDK code required.

It needs Python 3 with hidapi:

pip install hidapi

Tip

The tool talks to the device over HID, which stays available in every CDC mode. That is what makes it always possible to switch back out of a mode: even one like Terminal or Nova Compatible, where the COM port is busy doing something other than accepting settings commands.

Subcommands

Command	What it does
show	Print the current settings: webusb_enabled, cdc_enabled, cdc_mode.
set	Change one or more settings, then reset the device to persist them.
reset	Restore factory defaults (webusb=1, cdc=1, cdc_mode=0) and reset.

Flags

Flag	Applies to	Meaning
--cdc-mode <mode>	set	uart_passthrough, terminal, nova_compat, rs485, canfd, or the numeric value 0–4.
--cdc on|off	set	Enable or disable the CDC interface entirely.
--webusb on|off	set	Enable or disable WebUSB.
--device supernova|pulsar	all	Target one board when both are connected. Auto-detects otherwise.
--no-save	set	Apply in RAM only, without resetting. The change is lost on the next power cycle, and a cdc_mode change won’t take effect at all until a reset.

Common commands

# What mode is the device in right now?
python device_settings_cli.py show

# Switch modes: the device resets automatically to apply
python device_settings_cli.py set --cdc-mode terminal

# Go back to the default
python device_settings_cli.py set --cdc-mode uart_passthrough

# ...or restore everything to factory defaults
python device_settings_cli.py reset

# Target one board when both are plugged in
python device_settings_cli.py --device pulsar set --cdc-mode canfd

A successful set prints the updated settings and then resets the device:

Connected to Binho Supernova
Settings updated:
  webusb_enabled : 1  (on)
  cdc_enabled    : 1  (on)
  cdc_mode       : 1  (terminal)

Resetting device to persist settings to flash...
Device is resetting. Settings will be saved to flash.

Switching modes programmatically

The CLI is a thin wrapper over the SetUsbConfig HID command, which can be sent from Mission Control, a Binho SDK, or custom HID code. It carries three fields (webusb_enabled, cdc_enabled and cdc_mode), and each accepts 0xFF to mean “leave unchanged”.

SetUsbConfig only writes the setting. Send the reset command, or power-cycle the device, for the new mode to take effect.