Add BTHome energy monitor

Author: gfwilliams

apps.json

@@ -278,6 +278,18 @@
       {"name":".bootcde","url":"app.js"}
     ]
   },
+  { "id": "bthome_energy",
+    "name": "BTHome Energy Monitor",
+    "icon": "icon.png",
+    "version":"0.01",
+    "description": "Turn your Espruino device into a BTHome/Home Assistant compatible energy monitor by sensing flashes from your electricty meter (needs an LDR wired between D1 and D2)",
+    "tags": "bluetooth,homeassistant,energy,power,electricity",
+    "readme": "README.md",
+    "needsFeatures":["BLE"],
+    "storage": [
+      {"name":".bootcde","url":"app.js"}
+    ]
+  },
   { "id": "knobbutton",
     "name": "Knob Button",
     "icon": "icon.png",

apps/bthome_energy/ChangeLog

@@ -0,0 +1 @@
+0.01: New App!

apps/bthome_energy/README.md

@@ -0,0 +1,11 @@
+# BTHome Energy Monitor
+
+This advertises energy usage and battery in a [BTHome (https://bthome.io/)](https://bthome.io/) compatible format, which can then be used in https://www.home-assistant.io/
+
+This is based on https://www.espruino.com/BTHome and https://www.espruino.com/Smart+Meter
+
+## Usage
+
+With the device as on https://www.espruino.com/Smart+Meter, so an LDR between `D1` and `D2`, and position it over the flashing LED of an electricity meter.
+
+Install the app and disconnect, and a device called `Electricity` should appear in Home Assistant.

apps/bthome_energy/app.js

@@ -0,0 +1,37 @@
+var counter = 0; // number of impulses
+var power = 0; // power in watts (assuming 1000imp/kwh)
+var lastPulse = getTime();
+
+// Update BLE advertising
+function update() {
+  NRF.setAdvertising(require("BTHome").getAdvertisement([
+    {
+      type : "battery",
+      v : E.getBattery()
+    }, {
+      type : "energy",
+      v : counter/1000 // kWh, and usualy 1000 imp/kWh
+    }, {
+      type : "power",
+      v : power // kWh, and usualy 1000 imp/kWh
+    }
+  ]), {
+    name : "Electricity",
+    // not being connectable/scannable saves power (but you'll need to reboot to connect again with the IDE!)
+    //connectable : false, scannable : false,
+  });
+}
+
+// Set up pin states
+D1.write(0);
+pinMode(D2,"input_pullup");
+// Watch for pin changes
+setWatch(function(e) {
+  let timeDiff = e.time - lastPulse;
+  power = 3600 / timeDiff; // 1000imp/kwh -> 1000 pulses in 3600sec = 1kW
+  counter++;
+  update();
+  lastPulse = e.time;
+  digitalPulse(LED1,1,1); // show activity
+}, D2, { repeat:true, edge:"falling" });
+update();