Linux python read usb

python :Read from a USB HID device

I have a USB RFID device that appears on /dev/hidraw for my serial devices they appear on /dev/ttyUSB* i used pyserial and it works like charm but for this one i couldn’t read from it using cat /dev/hidraw0 need root privileges plus i need to read one line and not keep on listening I used evdev library but my device doesn’t appear at all :

import evdev devices = [evdev.InputDevice(fn) for fn in evdev.list_devices()] for device in devices: print(device.fn, device.name, device.phys) 

Your question is hard to read. Have a look at pyusb (of course you still need access rights to the device).

If cat /dev/hidraw0 can’t see it, it doesn’t sound good: you may have a defective device. Does it show up when you do lsusb in the terminal? Also check dmesg | tail after you plug it in. Note that even if lsusb can see it that doesn’t necessarily imply that you can actually do anything useful with the device. But if lsusb can’t see it, it’s probably dead.

i can read with the cat function but it needs root permission is there a way to read as normal user ?

The sudo cat /dev/hidrawX (hidraw3 in my case) worked nicely for me! Everytime the scanner recognized a barcode with the trigger, a string would pop out on terminal. Now that I did that sanity check, i can continue. Keep in mind I first used the Zebra config tool on windows to setup the scanner, I don’t know if that helped or not.

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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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Easy USB access for Python

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README.rst

PyUSB – Easy USB access for Python

PyUSB provides for easy access to the host machine’s Universal Serial Bus (USB) system for Python 3.

Until 0.4 version, PyUSB used to be a thin wrapper over libusb. Starting with the 1.0 version, things changed considerably: now PyUSB is an API rich, backend neutral Python USB module easy to use.

The best way to get started with PyUSB is to read the following documents:

For more detailed information, PyUSB’s API documentation, as with most Python modules, is based on Python doc strings and can be manipulated by tools such as pydoc [1]:

The libusb 1.0 documentation is also a recommended read, especially when using that backend (more on this below).

Requirements and platform support

PyUSB is primarily developed and tested on Linux and Windows, but it should also work fine on any platform running Python >= 3.7, ctypes and at least one of the built-in backends.

PyUSB supports libusb 1.0, libusb 0.1 and OpenUSB. Of those, libusb 1.0 is currently recommended for most use cases.

On Linux and BSD, these will generally be available on the distribution’s official repositories.

On macOS, libusb 1.0 can easily be installed through Homebrew:

On Windows, pyocd/libusb-package is a convenient [2] [3] way to provide the necessary libusb 1.0 DLL, as well as a suitable PyUSB backend and a easy to use wrapper over PyUSB’s find() API:

# with pure PyUSB for dev in usb.core.find(find_all=True): print(dev) # with pyocd/libusb-package for dev in libusb_package.find(find_all=True): print(dev)

Alternatively, the libusb 1.0 DLL can be manually copied from an official release archive into the C:\Windows\System32 system folder, or packaged together with the complete application.

PyUSB is generally installed through pip [1]:

# the latest official release python -m pip install pyusb # install a specific version (e.g. 1.2.1) python -m pip install pyusb==1.2.1 # the latest snapshop from the official git repository python -m pip install pyusb git+https://github.com/pyusb/pyusb#egg=pyusb

Most Linux distributions also package PyUSB in their official repositories.

If you have a question about PyUSB:

To report a bug or propose a new feature, use our issue tracker. But please search the database before opening a new issue.

[1]	(1, 2) On systems that still default to Python 2, replace python with python3 .

[2]	Unlike PyUSB, pyocd/libusb-package uses the more restrictive Apache 2.0 license.

[3]	While pyocd/libusb-package supports platforms other than Windows, there are advantages to sticking to a system-provided libusb, if it is available and the platform has a robust package manager (e.g. Linux, BSD, macOS with Homebrew).

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Easy USB access for Python

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