puck-energy-monitor.js

// Programmed with https://www.espruino.com/ide
// Based on https://github.com/aegjoyce/bthome-electricity-meter/blob/main/meter.js

var counter = 0;

// time in milliseconds since epoch
var lastpulse = Date.now();

// energy variable will be actual kWh * 1000 in order for BTHome to parse to 3 decimal places
var energy = 0;

// power variable will be actual watts * 100 in order for BTHome to parse to 2 decimal places
var power = 0;

// change this to match your meter - e.g. 3200 imp / kWh
var imp = 1000;

function onInit() {
  // Blink RED on init
  digitalPulse(LED1,1,100);

  // Tune battery life
  NRF.setTxPower(0);  // TODO: consider switching to -40
  //NRF.setConnectionInterval(1000);  // Not needed when using only advertising mode

  // Set up pin states
  D1.write(0);
  pinMode(D2,"input_pullup");

  E.enableWatchdog(5);

  clearWatch();
  // Watch for pin changes
  // Logic is inverted. "falling" is when signal is showing up, "rising" is when signal is fading.
  setWatch(function() {
    // Blink RED on signal detection
    digitalPulse(LED1,1,100);
    counter++;
    rate();
    update();
  }, D2, { repeat:true, edge:"falling" });

  /*
  // Baseline 60s update
  setInterval(function() {
    update();
  }, 60 * 1000);
  */

  // Blink GREEN after init is complete
  digitalPulse(LED2,1,100);
}

// Update BLE advertising
function update()   {
  NRF.setAdvertising(
    [
      // Reference - https://bthome.io/format/
      0x02,0x01,0x06,  // BTHome Identifier
      0x05,0x09,"P","u","c","k", // Local Name (Length + ID + name)
      0x0E,0x16,  // Service Data Header (Length + ID)
      0xD2,0xFC,  // BTHome UUID
      0x40,  // BTHome Device Information
      0x01,Puck.getBatteryPercentage(),  // Battery ID + Data
      0x0A,energy,energy>>8,energy>>16,  // Energy ID + Data
      0x0B,power,power>>8,power>>16,  // Power ID + Data
    ],{
      //interval: 600,
      scannable: false,
      connectable: false
    }
  );

  // Blink BLUE after update is complete
  digitalPulse(LED3,1,100);
}

// Calculate live wattage
function rate() {
  // make sure Date.now() is executed only once to ensure accurate calculations.
  now = Date.now();  // in milliseconds
  pulsetime = now - lastpulse;
  lastpulse = now;

  power = (360000000000 / imp) / pulsetime;
  power = Math.round(power);
  energy = counter * (1000 / imp);
  energy = Math.round(energy);
}