This project creates a USB HID keyboard with 4 rotary encoders and 13 button inputs. Instead of using keyboard keys, use toggle switches, ignition switches, etc. to make a car or airplane button box.
- https://learn.adafruit.com/rotary-encoder
- https://learn.adafruit.com/debouncer-library-python-circuitpython-buttons-sensors/overview
- https://learn.adafruit.com/circuitpython-essentials/circuitpython-hid-keyboard-and-mouse
Contents of the CIRCUITPY/lib directory. consumer_control*.mpy and mouse.mpy could be removed. rotaryio is a built-in library.
CIRCUITPY/lib
├── adafruit_debouncer.mpy
└── adafruit_hid
├── consumer_control_code.mpy
├── consumer_control.mpy
├── __init__.mpy
├── keyboard_layout_us.mpy
├── keyboard.mpy
├── keycode.mpy
└── mouse.mpy
In this example, the Raspberry Pi Pico is used because it exposes many GPIO pins on a $4 board. Other boards running CircuitPython can be used but the number of pins and the names of pins must be changed.
Note: This project uses 5 pin rotary encoders. KY-040 rotary encoder boards should work. It does not use Adafruit's Seesaw Rotary Encoder I2C boards.
Each rotary encoder has 3 pins on one side and 2 pins on the other. The 2 pins are ground and button output. The 3 pins are ground, A, and B.
The following table shows 4 rotary encoders are connected to a Raspberry Pi Pico board. The remaining pins are configured for button inputs.
The pin label refers the white text printed on back of the Pico. The CircuitPython (CP) pin name refers to the same pin but is the name used in CP programs.
0.A refers to rotary encoder 0 pin A and similarly for 0.B. 0.button refers to the button output pin. Note there are two pins for the button. One must be connected to ground and the other is the button output pin. It does not matter which is which. However, this is not true for the A and B pins. Swapping them reverses the direction of rotation so if an encoder behaves backwards, swapping the A and B pins should fix it.
| Rotary Encoder | Pico pin label | CP pin name |
|---|---|---|
| 0.A | GP0 | board.GP0 |
| 0.B | GP1 | board.GP1 |
| 0.button | GP8 | board.GP8 |
| 0.GND | GND | |
| 1.A | GP2 | board.GP2 |
| 1.B | GP3 | board.GP3 |
| 1.button | GP9 | board.GP9 |
| 1.GND | GND | |
| 2.A | GP4 | board.GP4 |
| 2.B | GP5 | board.GP5 |
| 2.button | GP10 | board.GP10 |
| 2.GND | GND | |
| 3.A | GP6 | board.GP6 |
| 3.B | GP7 | board.GP7 |
| 3.button | GP11 | board.GP11 |
| 3.GND | GND |
The remaining pins are handled as normally open push buttons. Each button must also have one its terminals connected to a Pico ground (GND).
| Plain Button | Pico pin label | CP pin name |
|---|---|---|
| B1 | GP12 | board.GP12 |
| B2 | GP13 | board.GP13 |
| B3 | GP14 | board.GP14 |
| B4 | GP16 | board.GP16 |
| B5 | GP17 | board.GP17 |
| B6 | GP18 | board.GP18 |
| B7 | GP19 | board.GP19 |
| B8 | GP20 | board.GP20 |
| B9 | GP21 | board.GP21 |
| B10 | GP22 | board.GP22 |
| B11 | GP26_A0 | board.GP26 |
| B12 | GP27_A1 | board.GP27 |
| B13 | GP28_A2 | board.GP28 |
The following table shows the USB keys sent by the Pico.
| USB Key | Action |
|---|---|
| F1 | Rotary encoder 0 clock wise rotation |
| F2 | Rotary encoder 0 counter clock wise rotation |
| F3 | Rotary encoder 1 clock wise rotation |
| F4 | Rotary encoder 1 counter clock wise rotation |
| F5 | Rotary encoder 2 clock wise rotation |
| F6 | Rotary encoder 2 counter clock wise rotation |
| F7 | Rotary encoder 3 clock wise rotation |
| F8 | Rotary encoder 3 counter clock wise rotation |
| F9 | Rotary encoder 0 button |
| F10 | Rotary encoder 1 button |
| F11 | Rotary encoder 2 button |
| F12 | Rotary encoder 3 button |
| F13 | Button 1 |
| F14 | Button 2 |
| F15 | Button 3 |
| F16 | Button 4 |
| F17 | Button 5 |
| F18 | Button 6 |
| F19 | Button 7 |
| INSERT | Button 8 |
| DELETE | Button 9 |
| HOME | Button 10 |
| END | Button 11 |
| PAGE_UP | Button 12 |
| PAGE_DOWN | Button 13 |