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Your project will use a specific set of CircuitPython libraries and the code.py file. To get everything you need, click on the Download Project Bundle link below, and uncompress the .zip file.
Drag the contents of the uncompressed bundle directory onto your board's CIRCUITPY drive, replacing any existing files or directories with the same names, and adding any new ones that are necessary.
# SPDX-FileCopyrightText: 2022 john park for Adafruit Industries
# SPDX-License-Identifier: MIT
# Pico Four Step Switch Keypad Demo
import time
import board
import keypad
from digitalio import Direction, DigitalInOut
board_led = DigitalInOut(board.LED)
board_led.direction = Direction.OUTPUT
board_led.value = True
switch_pins = (board.GP6, board.GP7, board.GP8, board.GP9)
keys = keypad.Keys(switch_pins, value_when_pressed=False, pull=True)
led_pins = (board.GP2, board.GP3, board.GP4, board.GP5)
leds = []
for led_pin in led_pins:
tmp_led_pin = DigitalInOut(led_pin)
tmp_led_pin.direction = Direction.OUTPUT
tmp_led_pin.value = False
leds.append(tmp_led_pin)
def blink_led(led_num, pause, repeat):
for __ in range(repeat * 2):
leds[led_num].value = not leds[led_num].value
time.sleep(pause)
def blink_all_leds(pause, repeat):
for __ in range(repeat * 2):
for led in leds:
led.value = not led.value
time.sleep(pause)
blink_all_leds(0.1, 4)
mode_picked = False # state of mode selection
mode_choice = 0 # MIDI mode, desk switcher mode, etc.
modes = (0, 1, 2, 3)
mode_names = ("MIDI", "DESK", "SELECTOR", "COPY-PASTE")
print("Select the mode by pressing a button: MIDI, DESK, SELECTOR, or COPY-PASTE")
while not mode_picked: # program waits for a mode to be picked
key = keys.events.get()
if key:
if key.pressed:
mode_choice = key.key_number
print(mode_names[mode_choice], "mode")
mode_picked = True
if mode_choice == 0: # MIDI mode
import usb_midi
import adafruit_midi
from adafruit_midi.control_change import ControlChange
midi = adafruit_midi.MIDI(
midi_in=usb_midi.ports[0],
in_channel=0,
midi_out=usb_midi.ports[1],
out_channel=0
)
cc_num = [16, 17, 18, 19]
cc_state = [False, False, False, False]
else: # HID modes
import usb_hid
from adafruit_hid.keyboard import Keyboard
from adafruit_hid.keycode import Keycode
if mode_choice == 1: # Mac Desktop switcher mode
kpd = Keyboard(usb_hid.devices)
MODIFIER = Keycode.CONTROL
KEYMAP = (
("Desktop 1", [MODIFIER, Keycode.ONE]),
("Desktop 2", [MODIFIER, Keycode.TWO]),
("Desktop 3", [MODIFIER, Keycode.THREE]),
("Desktop 4", [MODIFIER, Keycode.FOUR]),
)
if mode_choice == 2: # SELECTOR mode for game weapon slot, Wirecast, etc.
kpd = Keyboard(usb_hid.devices)
MODIFIER = Keycode.SHIFT
KEYMAP = (
("Selector 1", [MODIFIER, Keycode.ONE]),
("Selector 2", [MODIFIER, Keycode.TWO]),
("Selector 3", [MODIFIER, Keycode.THREE]),
("Selector 4", [MODIFIER, Keycode.FOUR]),
)
if mode_choice == 3: # Copy/Paste mode
kpd = Keyboard(usb_hid.devices)
# Choose the correct modifier key for Windows or Mac.
# MODIFIER = Keycode.CONTROL # For Windows
MODIFIER = Keycode.COMMAND
KEYMAP = (
("Copy/Paste 1", [MODIFIER, Keycode.A]), # select all
("Copy/Paste 2", [MODIFIER, Keycode.X]), # cut
("Copy/Paste 3", [MODIFIER, Keycode.C]), # copy
("Copy/Paste 4", [MODIFIER, Keycode.V]), # paste
)
blink_led(mode_choice, 0.1, 3)
while True:
key = keys.events.get()
if key:
if key.pressed:
i = key.key_number
print(i, "pressed")
if mode_choice == 0:
leds[i].value = not leds[i].value
if cc_state[i] is False:
midi.send(ControlChange(cc_num[i], 127))
cc_state[i] = True
else:
midi.send(ControlChange(cc_num[i], 0))
cc_state[i] = False
else:
print(KEYMAP[i][0])
kpd.send(*KEYMAP[i][1])
for switch_led in leds: # blank the LEDs first
switch_led.value = False
leds[i].value = True # light selected switch LED
Use It
On startup, the board waits for you to select a mode by pressing one of the four switches. From left-to-right the modes are "MIDI", "Desktop switcher", "Item selector", and "Copy-Paste".
- In MIDI mode pressing each key toggles a MIDI CC on and off (127 or 0). You can see this in action in the video at the top of the page
- Desktop switcher mode pick among four MacOS desk "Spaces". You can see a video of this mode demonstrated below.
- Selector mode pick four main items in many video games, particularly first-person shooters
- Copy-Paste mode invokes "select all", "cut", "copy", and "paste" shortcuts
How it Works
The code is doing a few basic tasks: checking for button presses, toggling the LEDs, and sending USB MIDI or USB HID messages.
To make the button reading simple, we use the adafruit_keypad library.
import time import board import keypad from digitalio import Direction, DigitalInOut
Switch Setup
The setup for multiple switches if very simple when using the keypad library. You create a variable name for the group of pins, list the pins, and then create a keypad object (in this case named keys) that point to the switch pin list, set a value default, and choose a pull up or down resistor value.
switch_pins = (board.GP6, board.GP7, board.GP8, board.GP9) keys = keypad.Keys(switch_pins, value_when_pressed=False, pull=True)
LED Setup
The LEDs are set up as a list so they are easy to call later using a list and index, e.g. leds[2]
led_pins = (board.GP2, board.GP3, board.GP4, board.GP5)
leds = []
for led_pin in led_pins:
tmp_led_pin = DigitalInOut(led_pin)
tmp_led_pin.direction = Direction.OUTPUT
tmp_led_pin.value = False
leds.append(tmp_led_pin)
Blink Functions
A couple of convenience functions are created to make it easy to blink one or all of the LEDs.
def blink_led(led_num, pause, repeat):
for __ in range(repeat * 2):
leds[led_num].value = not leds[led_num].value
time.sleep(pause)
def blink_all_leds(pause, repeat):
for __ in range(repeat * 2):
for led in leds:
led.value = not led.value
time.sleep(pause)
Mode Selection
At startup, the code will wait for the user to select one of four modes by clicking one of the step switches.
To do so, we have a mode_picked state, a mode_choice variable, and four possible modes.
Using a while not mode_picked: loop, the program essentially checks for a button press before it will get out of the loop and move ahead.
mode_picked = False # state of mode selection
mode_choice = 0 # MIDI mode, desk switcher mode, etc.
modes = (0, 1, 2, 3)
mode_names = ("MIDI", "DESK", "SELECTOR", "COPY-PASTE")
print("Select the mode by pressing a button: MIDI, DESK, SELECTOR, or COPY-PASTE")
while not mode_picked: # program waits for a mode to be picked
key = keys.events.get()
if key:
if key.pressed:
mode_choice = key.key_number
print(mode_names[mode_choice], "mode")
mode_picked = True
Modes
Once a mode is selected, additional libraries are imported relevant to the mode selection, as well as some other specific setup.
For mode 0, MIDI is set up, with a list of CC numbers to use.
if mode_choice == 0: # MIDI mode
import usb_midi
import adafruit_midi
from adafruit_midi.control_change import ControlChange
midi = adafruit_midi.MIDI(
midi_in=usb_midi.ports[0],
in_channel=0,
midi_out=usb_midi.ports[1],
out_channel=0
)
cc_num = [16, 17, 18, 19]
cc_state = [False, False, False, False]
The other three modes import USB hid libraries.
else: # HID modes
import usb_hid
from adafruit_hid.keyboard import Keyboard
from adafruit_hid.keycode import Keycode
if mode_choice == 1: # Mac Desktop switcher mode
kpd = Keyboard(usb_hid.devices)
MODIFIER = Keycode.CONTROL
KEYMAP = (
("Desktop 1", [MODIFIER, Keycode.ONE]),
("Desktop 2", [MODIFIER, Keycode.TWO]),
("Desktop 3", [MODIFIER, Keycode.THREE]),
("Desktop 4", [MODIFIER, Keycode.FOUR]),
)
if mode_choice == 2: # SELECTOR mode for game weapon slot, Wirecast, etc.
kpd = Keyboard(usb_hid.devices)
MODIFIER = Keycode.SHIFT
KEYMAP = (
("Selector 1", [MODIFIER, Keycode.ONE]),
("Selector 2", [MODIFIER, Keycode.TWO]),
("Selector 3", [MODIFIER, Keycode.THREE]),
("Selector 4", [MODIFIER, Keycode.FOUR]),
)
if mode_choice == 3: # Copy/Paste mode
kpd = Keyboard(usb_hid.devices)
# Choose the correct modifier key for Windows or Mac.
# MODIFIER = Keycode.CONTROL # For Windows
MODIFIER = Keycode.COMMAND
KEYMAP = (
("Copy/Paste 1", [MODIFIER, Keycode.A]), # select all
("Copy/Paste 2", [MODIFIER, Keycode.X]), # cut
("Copy/Paste 3", [MODIFIER, Keycode.C]), # copy
("Copy/Paste 4", [MODIFIER, Keycode.V]), # paste
)
Main Loop
When the main loop of the program is running the step switches are checked using the keys.events.get() command.
When a key is pressed, that switch's LED lights up and the associated command is sent.
while True:
key = keys.events.get()
if key:
if key.pressed:
i = key.key_number
print(i, "pressed")
if mode_choice == 0:
leds[i].value = not leds[i].value
if cc_state[i] is False:
midi.send(ControlChange(cc_num[i], 127))
cc_state[i] = True
else:
midi.send(ControlChange(cc_num[i], 0))
cc_state[i] = False
else:
print(KEYMAP[i][0])
kpd.send(*KEYMAP[i][1])
for switch_led in leds: # blank the LEDs first
switch_led.value = False
leds[i].value = True # light selected switch LED
Page last edited January 22, 2025
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