epd2in13/README.md

Nodejs driver for the Waveshare 2.13inch (B) e-Paper Hat

# epd2in13
This is a port of the epd2in13bc [Python driver from Waveshare](https://github.com/waveshare/e-Paper/tree/master/RaspberryPi_JetsonNano/python/lib/waveshare_epd).  
Key features of this library:
* Fast, uses native GPIO and SPI libraries
* Supports Red Color
* Remappable Pins
* Promises based
* Can render from a Canvas or an Image

Since this device is only capble of single tone (black or white, or red), it uses a frame buffer of 1 bit per pixel.  
Although this device natively uses a portrait layout per the diagram below, it is mapped to a landscape layout instead for practical rendering of images or canvas.  
Hence, Width > Height for `prepareImageFile` or `prepareCanvas` function calls.  
<a name="layout"></a>
![Layout](https://i.postimg.cc/6p9C1HpT/epd2in13-layout.png)

## In-Action Shot
![Action Shot](https://i.postimg.cc/SxfbmK4D/epd2in13.png)


## Dependencies
1. [GPIO](https://github.com/jperkin/node-rpio)
2. [SPI-Devicve](https://github.com/fivdi/spi-device)
3. [ImageJS](https://github.com/image-js/image-js) for buffer rendering

## Getting Started
  ```sh
  npm install epd2in13
  ```

## Example Code
```js
    const epd2in13 = require('epd2in13');
    const { createCanvas, registerFont } = require('canvas');

    const display = new epd2in13(); // Or potentially call new epd2in13({ RST_PIN: 10, BUSY_PIN: 11 }) if the pins are remapped for any reason

    // Setup the canvases and context here
    registerFont('./fonts/Montserrat-Medium.ttf', { family: 'Montserrat' });
    const black = createCanvas(display.width, display.height);
    const bctx = black.getContext('2d');
    const red = createCanvas(display.width, display.height);
    const rctx = red.getContext('2d');

    // Black context here
    bctx.fillStyle = 'white';
    bctx.fillRect(0, 0, display.width, display.height);
    bctx.font = '20px Montserrat';
    bctx.textBaseline = 'top';
    bctx.fillStyle = 'black';
    bctx.fillText('epd2in13 Driver', 5, 5);

    // Red context here
    rctx.fillStyle = 'white';
    rctx.fillRect(0, 0, display.width, display.height);
    rctx.fillStyle = 'black';
    rctx.fillRect(0, 35, 80, 16);
    rctx.font = '10px Montserrat';
    rctx.fillStyle = 'white';
    rctx.fillText('By gaweee', 5, 45);


    display.init()
        .then(() => display.clear())
        .then(() => Promise.all([display.prepareCanvas(black), display.prepareCanvas(red)]))
        .then(([blackBuffer, redBuffer]) => display.display(blackBuffer, redBuffer))
        .then((buffer) => display.wait())
        .then(() => display.clear())
        .then(() => display.prepareImageFile('./test.png'))
        .then((buffer) => display.display(buffer))
        .then((buffer) => display.wait())
        .then(() => display.clear())
        .then(() => display.sleep())
```

## Functions Calls
`epd2in13.init()`  
Runs the initialization sequence (Required).  

`epd2in13.reset()`  
Resets the display, runs already as part of the initialization sequence.  

`epd2in13.display(black=[], red=[])`  
Renders a combination of black and red optional buffers that follows a portrait layout.  
Refer to [layout diagram](#layout) above.  

`epd2in13.prepareCanvas`  
Translates the canvas into an image and sends to `prepareImageBuffer` call below.  

`epd2in13.prepareImageFile`  
Loads an image by fileaname and sends to `prepareImageBuffer` call below.  

`epd2in13.prepareImageBuffer`  
Takes in the image buffer and prepares it (pixel by pixel) for display, in the process maps the output from landscape to portrait layout.  

`epd2in13.clear(0xFF)`  
Flushes the screen to white, optionally send 0x00 for black.

`epd2in13.wait()`  
GPIO delay before the next event.  

`epd2in13.sleep()`  
Power down (retains ink on screen) the hat and stop listening to events.  

## TODO
* Abstract the driver to support multiple other displays in the future
* Optional rotation