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#!/usr/bin/env python2
# Send a BEEP command via USB to a Lego Mindstorms EV3 brick
import sys
import usb.core # https://walac.github.io/pyusb/
def ev3_write(command):
# To send commands, we need an Endpoint.
# To get to the endpoint we need to descend down the hierarchy of
# 1. Device
VENDOR_LEGO = 0x0694
PRODUCT_EV3 = 5
# 2. Configuration
CONFIGURATION_EV3 = 1 # 1-based
# 3. Interface
INTERFACE_EV3 = 0 # 0-based
# 4. Alternate setting
SETTING_EV3 = 0 # 0-based
# 5. Endpoint
ENDPOINT_EV3 = 1 # 0-based
# 1. Device
device = usb.core.find(idVendor=VENDOR_LEGO, idProduct=PRODUCT_EV3)
if device is None:
print("Is the brick connected and turned on?")
sys.exit(1)
# By default, the kernel will claim the device and make it available via
# /dev/usb/hiddevN and /dev/hidrawN which also prevents us
# from communicating otherwise. This removes these kernel devices.
# Yes, it is weird to specify an interface before we get to a configuration.
if device.is_kernel_driver_active(INTERFACE_EV3):
print("Detaching kernel driver")
device.detach_kernel_driver(INTERFACE_EV3)
# 2. Configuration
# A Device may have multiple Configurations, and only one can be active at
# a time. Most devices have only one. Supporting multiple Configurations
# is reportedly useful for offering more/less features when more/less
# power is available.
## Because multiple configs are rare, the library allows to omit this:
## device.set_configuration(CONFIGURATION_EV3)
configuration = device.get_active_configuration()
# 3. Interface
# A physical Device may have multiple Interfaces active at a time.
# A typical example is a scanner-printer combo.
#
# 4. Alternate setting
# I don't quite understand this, but they say that if you need Isochronous
# Endpoints (read: audio or video), you must go to a non-primary
# Alternate Setting.
interface = configuration[(INTERFACE_EV3, SETTING_EV3)]
# 5. Endpoint
# The Endpoint 0 is reserved for control functions
# so we use Endpoint 1 here.
# If an Interface uses multiple Endpoints, they will differ
# in transfer modes:
# - Interrupt transfers (keyboard): data arrives soon, with error detection
# - Isochronous transfers (camera): data arrives on time, or gets lost
# - Bulk transfers (printer): all data arrives, sooner or later
endpoint = interface[ENDPOINT_EV3]
# Finally!
endpoint.write(command)
beep_command = \
'\x0F\x00\x01\x00\x80\x00\x00\x94\x01\x81\x02\x82\xE8\x03\x82\xE8\x03'
ev3_write(beep_command)
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