BangleApps/apps/flagrse

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 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
• 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 to allow the servo motor to be controlled easily.

You might find the Espruino About Bluetooth LE page 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.