added distance measurer

docs/examples.md

@@ -212,5 +212,10 @@ Here are some fun programs for your @boardname@!
   "description": "Keep your brick entertained and happy",
   "url":"/examples/happy-unhappy",
   "cardType": "example"
+}, {
+  "name": "Distance Measurer",
+  "description": "Use a motor to measure angle and distance",
+  "url": "/examples/distance-measurer",
+  "cardType": "example"
 }]
 ```

docs/examples/distance-measurer.md

@@ -0,0 +1,34 @@
+# Distance Measurer
+
+```blocks
+let distance = 0
+let angle = 0
+let measuring = false
+let radius = 0
+// Start and stop measuring with the enter button
+brick.buttonEnter.onEvent(ButtonEvent.Pressed, function () {
+    if (measuring) {
+        // turn off the measuring
+        measuring = false
+        brick.setStatusLight(StatusLight.Off)
+    } else {
+        // turn on the measuring clear the counters so that
+        // the motor tracks the angle
+        measuring = true
+        motors.largeB.clearCounts()
+        brick.setStatusLight(StatusLight.GreenPulse)
+    }
+})
+radius = 2.5
+brick.showString("Press ENTER to measure", 4)
+forever(function () {
+    if (measuring) {
+        angle = motors.largeB.angle()
+        distance = angle / 180 * Math.PI * radius
+        brick.clearScreen()
+        brick.showValue("angle", angle, 2)
+        brick.showValue("distance", distance, 3)
+    }
+    pause(100)
+})
+```