Receiving/decoding more than 1 byte with ble_advert and known_services?

[HaLo2FrEeEk]

Is it possible? Am I just tripping? I know there are other ways of doing this, but I've gone down a rabbit hole and this is where I'm stuck. I want to advertise my current step count. I wrote a simple little boot app:

(() => {
  function advertiseSteps() {
    let s = Bangle.getHealthStatus("day").steps;

    //require("ble_advert").set(0xe1ba, s);   // method 1

    let steps = [s & 255,(s >> 8) & 255];     // method 2
    require("ble_advert").set(0xe1ba, steps); // method 2
  }

  setInterval(advertiseSteps, 60 * 1000);
  advertiseSteps();
})();

I also have/had this in my config.json:

"advertised_services" : {
  "e1ba" : {
    "name": "steps"
  }
},

There are a few problems. With the boot code how it is, I only get the first byte of the array (the low byte). If I remove the entry from advertised_services and restart EspruinoHub, then I don't get anything unless I enable "mqtt_advertise_service_data". If I uncomment method 1 and comment method 2 (with the entry in advertised_services), I get a mqtt messages like this:

/ble/advertise/Bangle/steps -> 18
/ble/advertise/Bangle/e1ba -> "[18]"
/ble/json/Bangle/e1ba -> "{\"steps\":18,\"rssi\":-64}"

And on the status page:

d8:6a:6b:c2:13:33 - Bangle.js 1333 (RSSI -76)
  180f => {"battery":93}
  e1ba => {"steps":18}
[CONNECT] Connections [] IDLE

The actual step count is 274. 274 & 255 = 18, so it's still only seeing the first byte. I don't know what else to try, I'd like to avoid using manufacturer data for this if I can.

I can see in /lib/attributes.js, the "decodeAttribute" function:

// look up decoders in config.json
if (name in config.advertised_services) {
  var srv       = config.advertised_services[name];
  var obj       = {};
  obj[srv.name] = value[0];
  return obj;
}

Which explains why I'm only getting the first byte when I have an entry in advertised_services, but I imagine there has to be a way to send values larger than 255, right?!

[gfwilliams]

I think I did mention in the last post you made was that using BTHome might be way easier for you, and it should handle this case pretty well?

As far as I remember with EspruinoHub it attempts to decode services it knows about, which are in https://github.com/espruino/EspruinoHub/blob/master/lib/attributes.js#L51

But it doesn't know e1ba - it seems you have a few options:

• Use 181c - which is 'User Data' and which I think gets passed though. Or any of the others on https://github.com/espruino/EspruinoHub/blob/master/lib/attributes.js#L31
• Add your own decoder to https://github.com/espruino/EspruinoHub/blob/master/lib/attributes.js#L51
• Use the 0x0590 manufacturer data
• Use mqtt_advertise_service_data in settings and it'll pass on all the service data it sees?

It looks like advertised_services does only do single bytes. Maybe the idea was it could be extended to include a data type but it looks like the person that added that code never got around to it.

[HaLo2FrEeEk]

I did try BTHome again, but unless I'm missing something I can't see how to set it up to advertise step count automatically. It's perfect for setting up buttons if I want to control someone in HA, but I don't think it's right for what I'm trying to do.

I did also eventually realize that /ble/advertise/Bangle/e1ba does send along both bytes with the mqtt_advertise_service_data option.

I ended up doing the dumbest thing. Home Assistant still only sees the first byte, so I subscribe to the /e1ba topic in Node-RED, use some simple js to turn the bytes into a 16-bit number, then send that back to Home Assistant. I also send an mqtt message to register the calculated step count as a new entity (just like EspruinoHub does) and I just disable the ones from /e1ba.

[gfwilliams]

Glad you got it working!

For BTHome the apps themselves don't have HRM broadcast built in, but it's pretty easy to use the app to add it. The BTHome app provides a function Bangle.btHome: https://github.com/espruino/BangleApps/blob/master/apps/bthome/boot.js#L18-L24

So you can just add the following to some boot code to make it advertise the current step count:

Bangle.on('step', function() { 
  let steps = Bangle.getHealthStatus("day").steps;
  Bangle.btHome([{type:"count16",v: steps}]);
});

[HaLo2FrEeEk]

Oh...well that changes everything! That would simplify my whole process! I'm definitely gonna take a closer look at BTHome again, thank you!

I also just realized that attributes.js is just a file. For some reason I had it in my head that I would have to rebuild EspruinoHome if I modified any of those files...now that I know I can change it and just restart, I might try adding my own handler. I would like to explore the option of making my own service with characteristic, mostly just for the learning. I know if I did that I would have to add it to attributes.js, but it would make it more worth it.

Now the thing I'm gonna bump my head against is that step count gets reset at midnight, but I work overnight so I'm not usually home at midnight. I might need to advertise both, current step count as well as yesterday's steps from the health app. Unless you know of a better solution?

I also just figured out how to send and evaluate JS, I couldn't get it to work before but I played with it more. I could eliminate even more of the process by just having Node-RED send the MQTT messages and receive the response. Hmmm, doors have opened for sure. Thank you for your help :)

[HaLo2FrEeEk]

Just wanted to give a little update. I edited the boot code to send both current and yesterday's steps in the same message, then I edited the attributes.js file to know what to do with the message. That was really all I needed to do.

I also set up a simple flow in Node-RED where I can send a message with "msg.js" as a string of Javascript that gets properly encoded, sends a notify and subscribes to the data topic, then sends the JS and unsubscribes 2 seconds after the last message is received (so I don't get overflowed when I connect to the IDE). It works most of the time, I know I could do it better, but it works well enough. It'll be handy for quick testing. Here's the flow for Node-RED:

[
    {
        "id": "f07a19d5b6f91c4c",
        "type": "mqtt in",
        "z": "aaeb6238.7944f",
        "g": "f1a04bc24ec88f64",
        "name": "",
        "topic": "",
        "qos": "2",
        "datatype": "auto-detect",
        "broker": "17ac1f27.2b5951",
        "nl": false,
        "rap": true,
        "rh": 0,
        "inputs": 1,
        "x": 595,
        "y": 280,
        "wires": [
            [
                "77db3fcab75455df"
            ]
        ],
        "l": false
    },
    {
        "id": "75cea28a7d12c011",
        "type": "function",
        "z": "aaeb6238.7944f",
        "g": "f1a04bc24ec88f64",
        "name": "function 85",
        "func": "let notify = {topic: \"/ble/notify/Bangle/nus/nus_rx\", payload: \"\"};\nlet sub = {topic: \"/ble/data/Bangle/nus/nus_rx\", action: \"subscribe\"}\n//let data = {topic: \"/ble/write/Bangle/nus/nus_tx\", payload: `Bangle.getHealthStatus(\"day\").steps\\n`};\nlet data = {topic: \"/ble/write/Bangle/nus/nus_tx\", payload: `${msg.js}\\n`};\n\nsetTimeout(() => node.send(data), 1000);\n\nreturn [notify, sub];",
        "outputs": 2,
        "timeout": 0,
        "noerr": 0,
        "initialize": "",
        "finalize": "",
        "libs": [],
        "x": 545,
        "y": 260,
        "wires": [
            [
                "d98c485dcd6ed883"
            ],
            [
                "f07a19d5b6f91c4c"
            ]
        ],
        "l": false
    },
    {
        "id": "77db3fcab75455df",
        "type": "function",
        "z": "aaeb6238.7944f",
        "g": "f1a04bc24ec88f64",
        "name": "function 86",
        "func": "let t = context.get(\"t\");\nif(!t) { context.set(\"t\", \"\"); t = context.get(\"t\"); }\nlet d = (context.get(\"d\")||\"\") + msg.payload;\n\nclearTimeout(t);\nt = setTimeout(() => {\n    node.send({topic: msg.topic, action: \"unsubscribe\"});\n    context.set(\"t\");\n    node.warn(d);\n    context.set(\"d\");\n}, 2000);\ncontext.set(\"t\", t);\ncontext.set(\"d\", d);\n\nreturn;",
        "outputs": 1,
        "timeout": 0,
        "noerr": 0,
        "initialize": "",
        "finalize": "",
        "libs": [],
        "x": 645,
        "y": 280,
        "wires": [
            [
                "f07a19d5b6f91c4c"
            ]
        ],
        "l": false
    },
    {
        "id": "3756823b6b1af241",
        "type": "inject",
        "z": "aaeb6238.7944f",
        "g": "f1a04bc24ec88f64",
        "name": "",
        "props": [
            {
                "p": "js",
                "v": "Bangle.getHealthStatus(\"day\").steps",
                "vt": "str"
            }
        ],
        "repeat": "",
        "crontab": "",
        "once": false,
        "onceDelay": 0.1,
        "topic": "",
        "x": 495,
        "y": 260,
        "wires": [
            [
                "75cea28a7d12c011"
            ]
        ],
        "l": false
    },
    {
        "id": "d98c485dcd6ed883",
        "type": "mqtt out",
        "z": "aaeb6238.7944f",
        "g": "f1a04bc24ec88f64",
        "name": "",
        "topic": "",
        "qos": "",
        "retain": "",
        "respTopic": "",
        "contentType": "",
        "userProps": "",
        "correl": "",
        "expiry": "",
        "broker": "17ac1f27.2b5951",
        "x": 595,
        "y": 240,
        "wires": [],
        "l": false
    },
    {
        "id": "17ac1f27.2b5951",
        "type": "mqtt-broker",
        "name": "Pi4 Broker",
        "broker": "192.168.0.140",
        "port": "1883",
        "clientid": "",
        "autoConnect": true,
        "usetls": false,
        "protocolVersion": "4",
        "keepalive": "60",
        "cleansession": true,
        "autoUnsubscribe": true,
        "birthTopic": "",
        "birthQos": "0",
        "birthPayload": "",
        "birthMsg": {},
        "closeTopic": "",
        "closeQos": "0",
        "closePayload": "",
        "closeMsg": {},
        "willTopic": "",
        "willQos": "0",
        "willPayload": "",
        "willMsg": {},
        "sessionExpiry": ""
    }
]

[gfwilliams]

That looks great - thanks for posting up! So with that it should be trivial to send updated time once a day if you need it.

If you want to send just a single steps value, you could either just detect if the steps value is lower than before, and instead add it - or, you can use Bangle.getStepCount() which will return the total number of steps single Bangle.js got hard rebooted.

[HaLo2FrEeEk]

I figure since EspruinoHub is doing the "hard" work of bridging the BLE and MQTT, I might just set up something in Node-RED that sends require("health").readDay(new Date(Date.now() - 86400000), print), when I get home from work. I can parse and process the array however I want and send the value along to HA.

Thank you for reminding me about updating the time! In all the whirlwind of learning I had completely forgotten that part of the goal lol. The NR flow will definitely make that easy!