Python usb core find

usb.core – USB Core

Initialize self. See help(type(self)) for accurate signature.

exception usb.core. USBTimeoutError 

Raised when a USB transfer times out.

Initialize self. See help(type(self)) for accurate signature.

usb.core. find ( find_all : bool = False , * , idVendor : int | None = None , idProduct : int | None = None ) → Device 

Find the first device that matches the given requirements or, if find_all is True, return a generator of all matching devices.

Returns None if no device matches.

User code cannot create Device objects. Instead, get them from usb.core.find .

The USB vendor ID of the device

The USB product ID of the device

The USB device’s serial number string.

The USB device’s product string.

The USB device’s manufacturer string.

set_configuration ( configuration = None ) 

Set the active configuration.

The configuration parameter is the bConfigurationValue field of the configuration you want to set as active. If you call this method without parameter, it will use the first configuration found. As a device hardly ever has more than one configuration, calling the method without arguments is enough to get the device ready.

write ( endpoint : int , data : circuitpython_typing.ReadableBuffer , timeout : int | None = None ) → int 

Write data to a specific endpoint on the device.

• endpoint (int) – the bEndpointAddress you want to communicate with.
• data (ReadableBuffer) – the data to send
• timeout (int) – Time to wait specified in milliseconds. (Different from most CircuitPython!)

the number of bytes written

read ( endpoint : int , size_or_buffer : array.array , timeout : int | None = None ) → int 

Read data from the endpoint.

• endpoint (int) – the bEndpointAddress you want to communicate with.
• size_or_buffer (array.array) – the array to read data into. PyUSB also allows size but CircuitPython only support array to force deliberate memory use.
• timeout (int) – Time to wait specified in milliseconds. (Different from most CircuitPython!)

ctrl_transfer ( bmRequestType : int , bRequest : int , wValue : int = 0 , wIndex : int = 0 , data_or_wLength : array.array | None = None , timeout : int | None = None ) → int 

Do a control transfer on the endpoint 0. The parameters bmRequestType, bRequest, wValue and wIndex are the same of the USB Standard Control Request format.

Control requests may or may not have a data payload to write/read. In cases which it has, the direction bit of the bmRequestType field is used to infer the desired request direction.

For host to device requests (OUT), data_or_wLength parameter is the data payload to send, and it must be a sequence type convertible to an array object. In this case, the return value is the number of bytes written in the data payload.

For device to host requests (IN), data_or_wLength is an array object which the data will be read to, and the return value is the number of bytes read.

Determine if CircuitPython is using the interface. If it is, the object will be unable to perform I/O.

interface (int) – the device interface number to check

Stop CircuitPython from using the interface. If successful, you will then be able to perform I/O. CircuitPython will automatically re-start using the interface on reload.

interface (int) – the device interface number to stop CircuitPython on

Allow CircuitPython to use the interface if it wants to.

interface (int) – the device interface number to allow CircuitPython to use

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How to Control USB Port using Python

Python, being a versatile programming language, can be used to interact with USB devices effectively.

This article will guide you through the process of controlling USB ports using Python, providing detailed explanations, and offering an example project to help you better explore its use cases.

Before we dive into the details of USB communication with Python, it’s essential to have a fundamental understanding of USB devices and how they function. This knowledge will help you work more effectively with USB devices and control them using Python.

To follow along with this tutorial, you should have a basic understanding of Python programming and some experience working with USB devices.

USB Basics

1. Understanding USB Devices

USB devices are connected to a computer or other host devices through USB ports. Each USB device has a unique identifier called the Vendor ID (VID) and Product ID (PID), which allows the host to recognize and communicate with it.

2. USB Device Communication

USB communication is based on a hierarchical structure, with the host being the primary controller and USB devices acting as slaves. Data transfers between the host and the devices occur through endpoints, which can be of different types, such as control, interrupt, bulk, or isochronous.

4. PyUSB Library

To interact with USB devices using Python, we will use the PyUSB library, which is a cross-platform module that simplifies USB communication in Python.

4.1. Installation

You can install the PyUSB library using pip:

4.2. Listing USB Devices

To list all connected USB devices, use the following code snippet:

import usb.core devices = usb.core.find(find_all=True) for device in devices: print("VID: , PID: ".format(device.idVendor, device.idProduct))

4.3. Device Information

To obtain detailed information about a specific USB device, you can use the following code snippet:

import usb.core device = usb.core.find(idVendor=0x1234, idProduct=0x5678) if device is None: print("Device not found") else: print("Device found") print("VID: , PID: ".format(device.idVendor, device.idProduct)) 

Replace `0x1234 and 0x5678` with the desired Vendor ID and Product ID.

Controlling USB

1. Reading from USB Devices

To read data from a USB device, you can use the following code snippet:

import usb.core import usb.util device = usb.core.find(idVendor=0x1234, idProduct=0x5678) if device is None: print("Device not found") else: # Set the configuration device.set_configuration() # Define the endpoint endpoint = device[0][(0, 0)][0] # Read data from the endpoint data = device.read(endpoint.bEndpointAddress, endpoint.wMaxPacketSize) print("Data read:", data) 

2. Writing to USB Devices

To write data to a USB device, use the following code snippet:

import usb.core import usb.util device = usb.core.find(idVendor=0x1234, idProduct=0x5678) if device is None: print("Device not found") else: # Set the configuration device.set_configuration() # Define the endpoint endpoint = device[0][(0, 0)][1] # Write data to the endpoint data = [0x01, 0x02, 0x03, 0x04] bytes_written = device.write(endpoint.bEndpointAddress, data) print("Bytes written:", bytes_written) 

3. Handling USB Exceptions

When working with USB devices, it’s crucial to handle exceptions that might occur. The following code snippet demonstrates how to catch and handle USB exceptions:

import usb.core import usb.util try: device = usb.core.find(idVendor=0x1234, idProduct=0x5678) if device is None: print("Device not found") else: # Set the configuration device.set_configuration() # Define the endpoint endpoint = device[0][(0, 0)][0] # Read data from the endpoint data = device.read(endpoint.bEndpointAddress, endpoint.wMaxPacketSize) print("Data read:", data) except usb.core.USBError as e: print("USB Error:", e) 

Example Project

1. Project Description

In this example project, we will create a simple Python script that reads data from a USB device and writes the data back to it.

2. Complete Code with Comments

import usb.core import usb.util # Find the USB device device = usb.core.find(idVendor=0x1234, idProduct=0x5678) if device is None: print("Device not found") else: try: # Set the configuration device.set_configuration() # Define the read endpoint read_endpoint = device[0][(0, 0)][0] # Read data from the read endpoint data = device.read(read_endpoint.bEndpointAddress, read_endpoint.wMaxPacketSize) print("Data read:", data) # Define the write endpoint write_endpoint = device[0][(0, 0)][1] # Write the data back to the write endpoint bytes_written = device.write(write_endpoint.bEndpointAddress, data) print("Bytes written:", bytes_written) except usb.core.USBError as e: print("USB Error:", e) 

3. Running the Project

To run the project, save the code in a file named usb_control_example.py and execute it using the following command:

python usb_control_example.py 

Make sure to replace the Vendor ID ( 0x1234 ) and Product ID ( 0x5678 ) with the correct values for your USB device.

Conclusion

In this article, we have covered the basics of USB devices and communication, and how to control USB ports using Python with the help of the PyUSB library. By following the provided examples and explanations, you should now be able to create your own Python projects to interact with USB devices effectively.

FAQs

Q1. Can I control all USB devices using Python?

A1. Python, with the help of the PyUSB library, allows you to control a wide range of USB devices. However, some devices may require additional drivers or specific communication protocols not covered in this article.

Q2. Can PyUSB be used on different operating systems?

A2. Yes, PyUSB is a cross-platform library that can be used on various operating systems, including Windows, macOS, and Linux.

Q3. How do I find the Vendor ID and Product ID of my USB device?

A3. You can use a tool like the Device Manager on Windows, System Information on macOS, or lsusb command on Linux to find the Vendor ID and Product ID of your USB device.

Q4. What are the different types of USB endpoints?

A4. There are four types of USB endpoints: control, interrupt, bulk, and isochronous. Each type serves a different purpose and has specific characteristics regarding data transfer rates and reliability.

Q5. Can I use Python to control USB devices other than storage devices?

A5. Yes, Python can be used to control various USB devices, including human interface devices (HID), such as keyboards and mice, as well as other peripherals, like printers and scanners.

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