Dial_Display: improve docs

Author: thyttan

modules/Dial_Display.md

@@ -0,0 +1,56 @@
+Bangle.js Dial Display Library
+======================
+
+
+> Take a look at README.md for hints on developing with this library.
+
+Usage
+-----
+
+```JS
+var DialDisplay = require("Dial_Display");
+var dialDisplay = new DialDisplay(options);
+```
+
+For example in use with the Dial module:
+
+```JS
+var options = {
+  stepsPerWholeTurn : 6,
+  dialRect : {
+    x: 0,
+    y: 0,
+    w: g.getWidth()/2,
+    h: g.getHeight()/2,
+  }
+}
+
+var DialDisplay = require("Dial_Display");
+var dialDisplay = new DialDisplay(options);
+
+var cb = (step)=>{
+  var value = dialDisplay(step);
+};
+
+var Dial = require("Dial");
+var dial = new Dial(cb, options)
+Bangle.on("drag", dial);
+```
+
+`options` (first argument) (optional) is an object containing:
+
+`stepsPerWholeTurn` - how many steps there are in one complete turn of the dial.
+`dialRect` - decides the area of the screen the dial is set up on.
+
+Defaults:
+```js
+{ stepsPerWholeTurn : 7
+  dialRect : {
+    x: 0,
+    y: 0,
+    w: g.getWidth(),
+    h: g.getHeight(),
+  },
+}
+```
+