# ScrollHat

Elixir driver for the Pimoroni Scroll Hat LED boards:

* [Scroll HAT mini](https://shop.pimoroni.com/products/scroll-hat-mini)
* [Scroll pHAT HD](https://shop.pimoroni.com/products/scroll-phat-hd)

See the [python library](https://github.com/pimoroni/scroll-phat-hd) also

## Usage

The main interface is via the `ScrollHat.Display` module which interacts
with the IS31FL3731 LED driver according to the pinout for the ScrollHat.

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Ensure you start the display to initialize the driver manually or in
your supervision tree:

```elixir
{:ok, _pid} = ScrollHat.Display.start_link()
```

The `draw/2` and `marquee/3` accept a 2D 7x17 canvas matrix where each value
represents the LED at that location starting from top-left. Values
must be a positive integer, 0-255, where `0` disables the LED and any value
greater than 0 sets the brightness to that level.

The `frame` argument is the frame (0-7) to write for the LED driver. The default
is the first frame `0`. However, this rarely needs to be used as it is mainly
intended as a memory store on the LED driver chip and is mainly provided for
convenience. The state of the display is instead kept in `ScrollHat.Display`

When using `marquee/3`, a canvas larger than 7x17 can be supplied in which
the display will attempt to scroll through, left -> right, moving one LED
column at a time.

A `ScrollHat.Font` has been provided as a convenience to transform text into
a canvas for display:

```elixir
canvas = ScrollHat.Font.graph("howdy")
ScrollHat.Display.draw(canvas)
```

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