Add flag raiser docs

apps.json

@@ -959,6 +959,7 @@
     "name": "Espruino Flag Raiser",
     "icon": "app.png",
     "version":"0.01",
+    "readme": "README.md",
     "description": "App to send a command to another Espruino to cause it to raise a flag",
     "tags": "",
     "storage": [

apps/flagrse/README.md

@@ -0,0 +1,76 @@
+# Espruino Flag Raiser
+
+An app to send a command to another Espruino to cause it to raise a flag.
+
+For this to work, you need to upload the following code to another
+bluetooth Espruino device (the one with the flag attached) :
+
+```
+var FLAG_PIN = D14;
+
+var s = require("servo").connect(FLAG_PIN);
+s.move(1,3000); // move to position 1 over 3 seconds
+
+var timeout;
+function flag() {
+  if (timeout) clearTimeout();
+  s.move(0.2,2000);
+  timeout = setTimeout(function() {
+    timeout = undefined;
+    s.move(1,2000);
+  },2000);
+}
+
+setWatch(flag, BTN, {repeat:true});
+
+NRF.setServices({
+  "3e440001-f5bb-357d-719d-179272e4d4d9": {
+    "3e440002-f5bb-357d-719d-179272e4d4d9": {
+      value : [0],
+      maxLen : 1,
+      writable : true,
+      onWrite : function(evt) {
+        flag();
+      }
+    }
+  }
+}, { uart : false });
+NRF.setAdvertising({}, {name:"Flag"});
+```
+
+## Wiring
+
+This is designed for an [MDBT42Q Breakout board](http://www.espruino.com/MDBT42Q)
+but should work on any Bluetooth LE Espruino device - you just need to change `FLAG_PIN`
+to the name of the pin that's connected to the servo motor.
+
+However, as designed:
+
+* Get an [MDBT42Q Breakout board](http://www.espruino.com/MDBT42Q)
+* Connect `GND` to GND (black) of a 3.7v LiPo battery
+* Connect `Vin` to positive (red) of the battery
+* Take a servo motor and:
+  * Connect the Black wire to `GND` (LiPo GND)
+  * Connect the Red wire to `Vin` (LiPo 3.7v)
+  * Connect the White wire to `D14` on the MDBT42Q
+
+## How does it work?
+
+The code above changes the advertised name of the Espruino device to be
+`Flag` (which the app then searches for).
+
+Then, it adds a service UUID `3e440001-f5bb-357d-719d-179272e4d4d9` (this
+is just a random number we made up) with characteristic `3e440002-f5bb-357d-719d-179272e4d4d9`
+(the same UUID with the second 16 bits incremented). When the characteristic
+is written (with any data), `flag()` is called, which raises the flag.
+
+`flag()` itself uses the [servo module](http://www.espruino.com/Servo+Motors)
+to allow the servo motor to be controlled easily.
+
+You might find the [Espruino About Bluetooth LE page](http://www.espruino.com/About+Bluetooth+LE)
+is useful as an introduction to services and characteristics.
+
+### Don't want to use a servo motor?
+
+No problem, just replace `flag()` with a function that controls whatever you need
+it to.