# Customizing USB Devices in CircuitPython ## Overview ## Standard CircuitPython USB Devices When you plug a CircuitPython board into a host computer, it shows up as several USB devices. Normally, you see: - The **CIRCUITPY** drive, which is a USB "Mass Storage" (MSC) device. - A serial connection to the REPL, which shows up as a **COM** port on Windows, a **/dev/tty** device on Linux, or a **/dev/cu** device on MacOS. - MIDI in and out streams, which show up as a kind of audio device. - A mouse, keyboard, etc., all of which are different kinds of "Human Interface Devices" (HID). The HID devices are lumped together in a single "composite" device. ## Can I Hide Some Devices? It's great that CircuitPython provides all these USB capabilities, **but sometimes you don't want to see all of them**. For instance, you might build a volume control, macro keypad, or your own fancy keyboard that you want to leave plugged in all the time. You wouldn't want its **CIRCUITPY** and serial connection to be visible. If you plugged in another CircuitPython board, you couldn't be sure which was your permanent accessory and which was the new board. So CircuitPython allows you to choose which devices are visible at run time. You add code to the **boot.py** file which will specifies which USB devices you want to enable or disable. You can [make CIRCUITPY disappear](https://learn.adafruit.com/customizing-usb-devices-in-circuitpython/circuitpy-midi-serial#circuitpy-mass-storage-device-3096583-4) or [hide the standard REPL serial connection](https://learn.adafruit.com/customizing-usb-devices-in-circuitpython/circuitpy-midi-serial#usb-serial-console-repl-and-data-3096590-12), for instance. Warning: Some CIrcuitPython boards use chips that provide no USB support or incomplete USB support. These boards may nevertheless have a USB jack which provides serial-only access. Examples include ESP32, ESP32-C3, ESP32-C6, and ESP32-P4 boards. The information in this guide does not apply to those boards. ## Add a Second Serial Port In addition to just turning the standard devices on and off, you can also [enable a second serial port](https://learn.adafruit.com/customizing-usb-devices-in-circuitpython/circuitpy-midi-serial#usb-serial-console-repl-and-data-3096590-12). A second **COM** port or **/dev/tty** or **/dev/cu** device will appear. It is not connected to the REPL, so you can use it for unimpeded communication back and forth with the host computer. You can send and receive binary data, and not worry about having to escape ctrl-C characters or seeing print statements or errors in the data you read. ## Define Custom HID Devices Finally, you can also [create new HID devices](https://learn.adafruit.com/customizing-usb-devices-in-circuitpython/hid-devices), such as specialized game controllers, digitizers, custom mice, and so forth. You'll need to understand how to make HID report descriptors, but you can often copy existing ones. ## Change USB Identification The overall USB device reports manufacturer and device names when it is plugged in. You can [change the default values if you wish](https://docs.circuitpython.org/en/latest/shared-bindings/supervisor/index.html#supervisor.set_usb_identification). A particular USB interface (MIDI, CDC, etc.) also reports names, but as of this writing, it is not possible to change these without building a custom version of CircuitPython. ## Try it! Read the rest of the guide to find out how to take control of CircuitPython USB! - [Next Page](https://learn.adafruit.com/customizing-usb-devices-in-circuitpython/circuitpy-midi-serial.md) ## Featured Products ### Adafruit Feather RP2040 [Adafruit Feather RP2040](https://www.adafruit.com/product/4884) A new chip means a new Feather, and the Raspberry Pi RP2040 is no exception. 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