Flex over USB

The Flex USB-B connection carries the robot’s HTTP API over serial, so no IP address is needed. Close the Opentrons App before connecting: it uses the same port.

Install serial support:

pip install 'pylabrobot[serial]'
python -m serial.tools.list_ports

Use the Flex’s port from that list (for example /dev/cu.usbmodem1201 on macOS; typically /dev/ttyACM0 on Linux or COM3 on Windows):

from pylabrobot.opentrons import Flex

flex = Flex(serial_port="/dev/cu.usbmodem1201")
await flex.connect()
try:
    print(flex.robot_model, flex.software_version)
finally:
    await flex.disconnect()

Run this in an async context or a notebook. connect() reads health without moving the robot. Supply either serial_port or host, not both. The usual setup() and pipette operations work through the selected transport; setup() homes the robot.

HTTPSerial reuses PLR’s HTTP logging, errors, and capture/replay. A serial timeout closes the port without retrying; check the robot’s state before reconnecting or repeating a command.