pyky040 0.1.4
High-level interface for the KY040 rotary encoder and switch.
Keywords: keyes rotary encoder switch ky040

# pyKY040

**High-level Python module for the KY040 rotary encoder and switch** on Raspberry Pi and similar boards that use `RPi.GPIO`

<img src="https://i.imgur.com/vgHjSoY.jpg" width="300" alt="KY-040 rotary encoder and switch">

## Features

- Increment callback
- Decrement callback
- Change callback (increment or decrement)
- Switch press callback

### Options

- Scale mode (internal counter is bound between X and Y, and is given as argument in the callback functions)
- Looped scale mode (from X to Y, then X again)
- Custom scale step
- GPIO polling (easier) or [as a device](#device-or-gpio-polling) (sturdier)

## Installation

```bash
pip install pyky040
```

## Usage

[![asciicast](https://asciinema.org/a/GVUyrqUUnZP4Sne8eEmKTWHCt.svg)](https://asciinema.org/a/GVUyrqUUnZP4Sne8eEmKTWHCt)

### Basic

```python
# Import the module
from pyky040 import pyky040

# Define your callback
def my_callback(scale_position):
    print('Hello world! The scale position is {}'.format(scale_position))

# Init the encoder pins
my_encoder = pyky040.Encoder(CLK=17, DT=18, SW=26)

# Or the encoder as a device (must be installed on the system beforehand!)
# my_encoder = pyky040.Encoder(device='/dev/input/event0')

# Setup the options and callbacks (see documentation)
my_encoder.setup(scale_min=0, scale_max=100, step=1, chg_callback=my_callback)

# Launch the listener
my_encoder.watch()

# Mess with the encoder...
# > Hello world! The scale position is 1
# > Hello world! The scale position is 2
# > Hello world! The scale position is 3
# > Hello world! The scale position is 2
# > Hello world! The scale position is 1
```

### In a thread

As the `watch()` method runs an infinite polling loop, you might want to run it in a thread if you don't want to block the rest of your script, or if you have **multiple encoders** to handle.

```python
# Import the module and threading
from pyky040 import pyky040
import threading

# Define your callback
def my_callback(scale_position):
    print('Hello world! The scale position is {}'.format(scale_position))

# Init the encoder pins
my_encoder = pyky040.Encoder(CLK=17, DT=18, SW=26)

# Or the encoder as a device (must be installed on the system beforehand!)
# my_encoder = pyky040.Encoder(device='/dev/input/event0')

# Setup the options and callbacks (see documentation)
my_encoder.setup(scale_min=0, scale_max=100, step=1, chg_callback=my_callback)

# Create the thread
my_thread = threading.Thread(target=my_encoder.watch)

# Launch the thread
my_thread.start()

# Do other stuff
print('Other stuff...')
while True:
    print('Looped stuff...')
    sleep(1000)
# ... this is also where you can setup other encoders!

# Mess with the encoder...
# > Other stuff...
# > Looped stuff...
# > Hello world! The scale position is 1
# > Hello world! The scale position is 2
# > Hello world! The scale position is 3
# > Looped stuff...
# > Hello world! The scale position is 2

```

**Note:** The interruption of the module when running in threads is not yet handled, you might have to kill it by yourself ��

## Documentation

#### `Encoder(CLK=x, DT=y, SW=z)`

Initializes the module with the specified encoder pins.

- Options
  - `polling_interval` Specify the pins polling interval in ms (default 1ms)

#### `Encoder(device='...')`

⚠️ Linux only

Initializes the module with the specified encoder device. [Read more](#device-or-gpio-polling)

Requirement: `pip install pyky040[device]`

#### `Encoder.setup()`

Setup the behavior of the module. All of the following keyword arguments are optional.

- Callbacks
  - `inc_callback (function)` When the encoder is incremented (clockwise). Scale position as first argument.
  - `dec_callback (function)` When the encoder is decremented. Scale position as first argument.
  - `chg_callback (function)` When the encoder is either incremented or decremented. Scale position as first argument.
  - `sw_callback (function)` When the encoder switch is pressed

- Scale mode
  - `scale_min (int/float)` Scale minimum
  - `scale_max (int/float)` Scale maximum
  - `loop (boolean)` Loop mode (defaults to `False`)
  - `step (int/float)` Scale step when incrementing or decrementing

- Options
  - `sw_debounce_time (int/float)` Switch debounce time in ms (allow only one interrupt per X ms, dismiss others)

**Note:** better keep using ints and not floats for more precise results.

#### `Encoder.watch()`

Starts the listener. The pins polling interval is `1ms` by default and can be customized (see `Encoder()`).

## <a name="device-or-gpio-polling"></a>Should I use the GPIO polling or the device overlay?

The Raspberry Pi firmware allows the encoder to be set up as a device with the [`rotary-encoder` overlay](https://github.com/raspberrypi/firmware/blob/master/boot/overlays/README#L1892-L1921). It trades *the promise to catch every encoder tick* for *the ease of use* (because it needs to be installed on the host beforeheand, with root privileges).

|Approach|Plug & Play|Needs prior installation|Catches every tick|
|--------|-----------|------------------------|---------------------|
|GPIO polling|**Yes**|No|No|
|Device overlay|No|Yes|**Yes**|

### <a name="install-device"></a>How to install the encoder as a device?

Only tested on Raspbian Buster at this time.

```
# Copy this line in `/boot/config.txt` and reboot
# (replacing {CLK_PIN} and {DT_PIN} by their real values)
dtoverlay=rotary-encoder,pin_a={CLK_PIN},pin_b={DT_PIN},relative_axis=1,steps-per-period=2
```

## TROUBLESHOOTING

### Erratic behavior

It is known that some pins combinations introduce erratic behavior (interferences?). The library has been tested successfully using the following combinations (BCM numbering).

|CLK| DT| SW|       Pi|Raspbian|
|---|---|---|---------|--------|
| 26|  4| 21| 3B (1.2)|Buster  |

Feel free to edit the README to provide your working combinations!

If you are still experiencing issues, you might want to try to [set up the encoder as a device](#device-or-gpio-polling) instead.

## CHANGELOG

**0.1.4**

  - Added `device` mode

**0.1.3**

  - Fixed `latest_switch_call` not defined before the loop

**0.1.2**

  - Changed `__init_` args to kwargs for better readability and ease of use `Encoder(CLK=x, DT=y, SW=z)`
  - Added customizable debounce time (in ms) for the switch `setup(..., sw_debounce_time=300)`
  - Added customizable polling interval (in ms) `Encoder(..., polling_interval=1)`