Get Battery Level and RSSI in JavaScript

devedag · July 2018

I need to query the Battery Level after the MetaMotionR is found. I also want to query the RSSI value each second.

How can I do this using JavaScript?

Eric · July 2018

https://mbientlab.com/cppdocs/0/settings.html#battery-state
https://github.com/noble/noble#update-rssi

devedag · July 2018

Thanks Eric, but it´s still not clear to me how to realize it in JavaScript.

Regarding the battery, this is my approach:

function batteryHandler(board, onDataCallback){
  battery_signal = MetaWear.mbl_mw_settings_get_battery_state_data_signal(board);
  MetaWear.mbl_mw_datasignal_subscribe(battery_signal, MetaWear.FnVoid_DataP.toPointer(onDataCallback));
  MetaWear.mbl_mw_datasignal_read(battery_signal);
}

let onBatteryDataCallback = (data) => {
    let state = data.deref().value;
        console.log(state);     // prints another Buffer <Buffer@0x1a2e3d8 >
};
ServiceMeMoHardware.batteryHandler(newMeMo.board, onBatteryDataCallback);

How can I realize the inner part?

auto state = (MblMwBatteryState*) data->value;
printf("{voltage: %dmV, charge: %d}\n", state->voltage, state->charge);

devedag · July 2018

Ok, I was thinking too quick, got the battery query work now:

      let onBatteryDataCallback = (dataPtr) => {
        let data = dataPtr.deref();
        let MblMwBatteryState = data.parseValue();
        /* MblMwBatteryState Public Attributes
            voltage: Voltage level [mV]
            charge: 0-100 [%]
        */
        console.log('Charge ' + MblMwBatteryState.charge + '%');
      };
      ServiceMeMoHardware.batteryHandler(newMeMo.board, onBatteryDataCallback);

For the RSSI issue I don't really see any approach... I need to get the new RSSi value each time it changes...

    peripheral.once('rssiUpdate', callback(rssi));
    peripheral.updateRssi([callback(error, rssi)]);

How can I use the Noble functions? Could someone please provide a quick JavaScript example?

Eric · July 2018

You should check the Noble GtiHub repo for code examples / ask Noble specific questions there.

mraxn · November 2018

Hi Eric,

Is there is a simple way to get the one time off battery level of sensor, without subscribing to periodic updates? I've noticed the MetaWear.BatteryState but haven't figured out how to use it... I noticed above that you referencing to C++ API but I don't understand how to use examples from C++ in JavaScript...

Eric · November 2018

@mraxn said:
Hi Eric,

Is there is a simple way to get the one time off battery level of sensor, without subscribing to periodic updates? I've noticed the MetaWear.BatteryState but haven't figured out how to use it... I noticed above that you referencing to C++ API but I don't understand how to use examples from C++ in JavaScript...

Look at the code posted in this thread.

Get Battery Level and RSSI in JavaScript

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