How can I make the Raspberry Pico not automount as USB storage while using Circuit Python

user_15254934 0
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I am using Circuit Python on a Raspberry Pi Pico to give me hardware buttons for keyboard shortcuts. I am using Circuit Python as opposed to MicroPython because it has the USB_HID library.

I don't want the Pico to automatically mount as USB storage when being plugged in. I just want it to act as a HID device. I am aware that I can write a boot.py script in addition to a code.py but I can't find anywhere online what to put in this which would prevent it from mounting as a USB device. I also still want it to mount as USB sometimes (when a button is pressed/GPIO pin is connected) so there is a still a way for me to change the code on the device.

Is this possible? And, if so, what should the boot.py look like to only mount when a certain GPIO pin is connected?

adafruit-circuitpython raspberry-pi-pico raspberry-pi python
3 Answers

I recently came across a need to do the same that you are looking for, and after a decent rabbit hole, have determined that it can't be done at this time.

https://github.com/adafruit/circuitpython/issues/1015

Looks like the request was opened a few years ago and is still listed as open.

I am not sure if running a pi zero in "gadget" mode can accomplish this or not, but may be worth a look

user_131731810

The code below is what I use. Roughly, it checks to see if a button connected to one of the Pico's IO pins. If the button is pressed when the cable is plugged in, then it mounts as a USB drive. If the button is not pressed, it's not mounted:

import storage
import board, digitalio

# If not pressed, the key will be at +V (due to the pull-up).
# https://learn.adafruit.com/customizing-usb-devices-in-circuitpython/circuitpy-midi-serial#circuitpy-mass-storage-device-3096583-4
button = digitalio.DigitalInOut(board.GP2)
button.direction = digitalio.Direction.INPUT
button.pull = digitalio.Pull.UP

# Disable devices only if button is not pressed.
if button.value:
    print(f"boot: button not pressed, disabling drive")
    storage.disable_usb_drive()

This was adapted from examples on Adafruit's site

user_1387760

Here's a good HID guide:

https://learn.adafruit.com/circuitpython-essentials/circuitpython-hid-keyboard-and-mouse

Here's the HID example:

import time

import board
import digitalio
import usb_hid
from adafruit_hid.keyboard import Keyboard
from adafruit_hid.keyboard_layout_us import KeyboardLayoutUS
from adafruit_hid.keycode import Keycode

# A simple neat keyboard demo in CircuitPython

# The pins we'll use, each will have an internal pullup
keypress_pins = [board.A1, board.A2]
# Our array of key objects
key_pin_array = []
# The Keycode sent for each button, will be paired with a control key
keys_pressed = [Keycode.A, "Hello World!\n"]
control_key = Keycode.SHIFT

# The keyboard object!
time.sleep(1)  # Sleep for a bit to avoid a race condition on some systems
keyboard = Keyboard(usb_hid.devices)
keyboard_layout = KeyboardLayoutUS(keyboard)  # We're in the US :)

# Make all pin objects inputs with pullups
for pin in keypress_pins:
    key_pin = digitalio.DigitalInOut(pin)
    key_pin.direction = digitalio.Direction.INPUT
    key_pin.pull = digitalio.Pull.UP
    key_pin_array.append(key_pin)

# For most CircuitPython boards:
led = digitalio.DigitalInOut(board.D13)
# For QT Py M0:
# led = digitalio.DigitalInOut(board.SCK)
led.direction = digitalio.Direction.OUTPUT

print("Waiting for key pin...")

while True:
    # Check each pin
    for key_pin in key_pin_array:
        if not key_pin.value:  # Is it grounded?
            i = key_pin_array.index(key_pin)
            print("Pin #%d is grounded." % i)

            # Turn on the red LED
            led.value = True

            while not key_pin.value:
                pass  # Wait for it to be ungrounded!
            # "Type" the Keycode or string
            key = keys_pressed[i]  # Get the corresponding Keycode or string
            if isinstance(key, str):  # If it's a string...
                keyboard_layout.write(key)  # ...Print the string
            else:  # If it's not a string...
                keyboard.press(control_key, key)  # "Press"...
                keyboard.release_all()  # ..."Release"!

            # Turn off the red LED
            led.value = False

    time.sleep(0.01) ```

The example only prints Hello World, so it's not very useful, but it's a good base to mod.
user_161558010
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