Transports

Overview

The SDK exposes four transport constructors:

Constructor	Protocol	Use Case
`Controller(channel)`	SocketCAN	Standard CAN 2.0, most common
`Controller.from_socketcanfd(channel)`	CAN-FD	High-bandwidth, Hexfellow motors
`Controller.from_dm_serial(port, baud)`	Serial	Damiao serial bridge adapter
`Controller.from_dm_device(dm_device_type, dm_channel)`	DM_Device SDK	Damiao via USB2CANFD / USB2CANFD_DUAL / LINKX4C

SocketCAN (Standard CAN)

The default transport for most motor vendors. Linux uses SocketCAN directly, and Windows/macOS use the PCAN backend with canX channel aliases.

Usage

from motorbridge import Controller

# Open standard CAN interface
with Controller("can0") as ctrl:
    motor = ctrl.add_damiao_motor(0x01, 0x11, "4340P")
    # ... control motor

Supported Vendors

Damiao (all models)
RobStride
MyActuator
HighTorque

System Setup (3 Platforms)

Linux (SocketCAN):

# Configure CAN interface at 1M bitrate
sudo ip link set can0 type can bitrate 1000000
sudo ip link set can0 up

# Increase TX queue to prevent buffer overflow
sudo ifconfig can0 txqueuelen 1000

macOS (PCAN via PCBUSB):

# Verify PCBUSB runtime is available
python3 -c "import ctypes; ctypes.CDLL('libPCBUSB.dylib'); print('PCBUSB load OK')"

# Run a scan check on can0
motorbridge-cli scan --vendor damiao --transport auto --channel can0 --start-id 1 --end-id 16

Windows (PCAN):

# Verify PCAN runtime is available
python -c "import ctypes; ctypes.CDLL('PCANBasic.dll'); print('PCANBasic load OK')"

# can0@1000000 maps to PCAN_USBBUS1
motorbridge-cli scan --vendor damiao --transport auto --channel can0@1000000 --start-id 1 --end-id 16

Multiple CAN Interfaces

# Control motors on different CAN buses
with Controller("can0") as ctrl0:
    motor0 = ctrl0.add_damiao_motor(0x01, 0x11, "4340P")

with Controller("can1") as ctrl1:
    motor1 = ctrl1.add_robstride_motor(127, 0xFD, "rs-06")

CAN-FD (SocketCAN-FD)

Extended CAN with larger payload and higher bandwidth. Required for some vendors.

Usage

from motorbridge import Controller

# Open CAN-FD interface
with Controller.from_socketcanfd("can0") as ctrl:
    motor = ctrl.add_hexfellow_motor(0x01, 0x00, "hexfellow")
    # ... control motor

Supported Vendors

Hexfellow (required)
Damiao (optional, for higher bandwidth)

System Setup

# Configure CAN-FD interface
sudo ip link set can0 type can bitrate 1000000 dbitrate 5000000 fd on
sudo ip link set can0 up

CAN-FD examples above are Linux-first. On Windows/macOS, prefer standard CAN (Controller(channel)) unless your adapter stack explicitly supports FD.

DM Serial Bridge

Serial-to-CAN bridge for Damiao motors using the official Damiao serial adapter.

Usage

from motorbridge import Controller

# Open serial bridge
with Controller.from_dm_serial("/dev/ttyACM0", baud=921600) as ctrl:
    motor = ctrl.add_damiao_motor(0x01, 0x11, "4340P")
    # ... control motor

Parameters

Parameter	Type	Default	Description
`serial_port`	str	”/dev/ttyACM0”	Serial device path
`baud`	int	921600	Baud rate (use 921600 for Damiao)

Supported Vendors

Damiao only

Serial Port Setup (3 Platforms)

Linux:

# Check available serial ports
ls -la /dev/ttyACM* /dev/ttyUSB*

# Add user to dialout group for permission
sudo usermod -a -G dialout $USER
# Log out and back in

macOS:

# Typical serial devices
ls -la /dev/cu.usbmodem* /dev/cu.usbserial*

Windows (PowerShell):

# List COM ports
[System.IO.Ports.SerialPort]::GetPortNames()

Common Serial Devices

Device	Path	Notes
Damiao USB-CAN	/dev/ttyACM0	Default
USB-Serial Adapter	/dev/ttyUSB0	Check with `dmesg`

DM-Device (DM_Device SDK)

Native Damiao transport backed by the DaMiao DM_Device SDK for the USB2CANFD, USB2CANFD_DUAL, and LINKX4C adapters. The adapter must be in USB mode; this transport is Damiao-only.

Usage

from motorbridge import Controller

# Open DM-Device transport
with Controller.from_dm_device("usb2canfd", dm_channel="0") as ctrl:
    motor = ctrl.add_damiao_motor(0x01, 0x11, "4340P")
    # ... control motor

Parameters

Parameter	Type	Default	Description
`dm_device_type`	str	—	`usb2canfd`, `usb2canfd-dual`, or `linkx4c`
`dm_channel`	str	`"0"`	Channel index (string). `usb2canfd`: `"0"`; `usb2canfd-dual`: `"0"`/`"1"`; `linkx4c`: `"0"`..`"3"`.

Supported Vendors

Damiao only

Runtime Requirements

Python wheels do not embed the vendor runtime. If the DM_Device runtime is missing, MotorBridge prints the required runtime file, its GitHub download URL, where to place it, and the platform ABI requirements.

Linux x86_64: libusb-1.0.so.0, GLIBC_2.14+, libstdc++.so.6 with GLIBCXX_3.4.32
Linux aarch64: GLIBC_2.17+, libstdc++.so.6 with GLIBCXX_3.4.22+

Install the runtime on demand with the bundled helper:

motorbridge-install-dm-device

Windows DM_Device runtime selection is restricted to x86_64. Long-running processes reuse the already-open adapter instead of reopening it.

Transport Selection Guide

Decision Tree

What motor vendor are you using?
│
├── Hexfellow ──→ from_socketcanfd (required)
│
├── Damiao with USB2CANFD / USB2CANFD_DUAL / LINKX4C ──→ from_dm_device
│
├── Damiao with USB-CAN adapter ──→ from_dm_serial
│
├── Damiao with CAN card ──→ Controller (SocketCAN)
│
├── RobStride ──→ Controller (SocketCAN)
│
├── MyActuator ──→ Controller (SocketCAN)
│
└── HighTorque ──→ Controller (SocketCAN)

Mixed Vendor Setup

When using multiple vendors on the same CAN bus, create separate Controller instances:

from motorbridge import Controller

# Each vendor gets its own controller
with Controller("can0") as dm_ctrl:
    dm_motor = dm_ctrl.add_damiao_motor(0x01, 0x11, "4340P")
    dm_ctrl.enable_all()

with Controller("can0") as rs_ctrl:
    rs_motor = rs_ctrl.add_robstride_motor(127, 0xFD, "rs-06")
    rs_ctrl.enable_all()

Do not add motors from different vendors to the same Controller instance. Each controller is optimized for a specific vendor protocol.

Transport Performance

Latency Comparison

Transport	Typical Latency	Max Throughput
SocketCAN	~1-2 ms	~5000 msg/s
CAN-FD	~0.5-1 ms	~10000 msg/s
DM Serial	~2-5 ms	~2000 msg/s
DM-Device	~1-2 ms	~5000 msg/s

Recommendations

Real-time control: Use SocketCAN or CAN-FD
Development/Debug: DM Serial is convenient for quick testing
High-speed loops: Use CAN-FD with dt_ms >= 10

Troubleshooting

SocketCAN: “No buffer space available” (Error 105)

# Stop other CAN senders
# Increase TX queue
sudo ifconfig can0 txqueuelen 1000

# Increase control loop period
# dt_ms = 20 or higher

Serial: Permission Denied

sudo usermod -a -G dialout $USER
# Log out and back in

CAN-FD: “Invalid argument”

# Ensure CAN-FD is enabled on interface
sudo ip link set can0 type can bitrate 1000000 dbitrate 5000000 fd on
sudo ip link set can0 up

Next Steps

Quickstart - Your first motor control program
API: Controller - Full controller API reference

​Transports

​Overview

​SocketCAN (Standard CAN)

​Usage

​Supported Vendors

​System Setup (3 Platforms)

​Multiple CAN Interfaces

​CAN-FD (SocketCAN-FD)

​Usage

​Supported Vendors

​System Setup

​DM Serial Bridge

​Usage

​Parameters

​Supported Vendors

​Serial Port Setup (3 Platforms)

​Common Serial Devices

​DM-Device (DM_Device SDK)

​Usage

​Parameters

​Supported Vendors

​Runtime Requirements

​Transport Selection Guide

​Decision Tree

​Mixed Vendor Setup

​Transport Performance

​Latency Comparison

​Recommendations

​Troubleshooting

​SocketCAN: “No buffer space available” (Error 105)

​Serial: Permission Denied

​CAN-FD: “Invalid argument”

​Next Steps

Transports

Overview

SocketCAN (Standard CAN)

Usage

Supported Vendors

System Setup (3 Platforms)

Multiple CAN Interfaces

CAN-FD (SocketCAN-FD)

Usage

Supported Vendors

System Setup

DM Serial Bridge

Usage

Parameters

Supported Vendors

Serial Port Setup (3 Platforms)

Common Serial Devices

DM-Device (DM_Device SDK)

Usage

Parameters

Supported Vendors

Runtime Requirements

Transport Selection Guide

Decision Tree

Mixed Vendor Setup

Transport Performance

Latency Comparison

Recommendations

Troubleshooting

SocketCAN: “No buffer space available” (Error 105)

Serial: Permission Denied

CAN-FD: “Invalid argument”

Next Steps