device-decoder

device-decoder is a JavaScript library for uniformly and efficiently working with streaming devices on web pages and native apps. It is multithreaded by default with dedicated codec threads, serial threads, and can be used with custom codecs you write following our conventions.

This supports Web Bluetooth API + Native Mobile (via @capacitor-community/bluetooth-le) and Web Serial API using convenient wrappers.

Note: Android has severe limits with Web Bluetooth (e.g. 20 byte MTU limit, 512 byte limit elsewhere) so the native library is necessary for mobile builds.

Packages

• device-decoder is the main package for decoding and rendering data from streaming devices (source)
• ble-wrapper wraps @capacitor-community/bluetooth-le with easier handles (source)
• webserial-wrapper wraps the Web Serial API with easy handles and buffering + transform stream support (source)
• device-decoder.third_party contains wrappers for third party libraries. Includes Muse, Ganglion, and Webgazer (eye tracking) (source). Import Devices from this to get a complete device list including these extra, much fatter drivers.

Examples

• A general purpose debugger for BLE and USB streaming devices (source, website)
• An EEG acquisition system with filters and coherence analysis (source)
• An HEG-FNIRS acquisition system with auditory feedback (source)
• A multimodal data acquisition system with alerts for specific sensors (source, website)

Installation

You can use the device-decoder library in your project in a few different ways.

If you're using NPM to manage your project, you can install the library with the following command:

npm install device-decoder

Otherwise, it may be more convenient to use a CDN link to import the library directly into your project:

<script src="https://cdn.jsdelivr.net/npm/device-decoder@latest/dist/device.frontend.esm.js"></script>

Regardless of your import source, you may find it useful to use ES Modules to explicitly include variables from the library in your code:

import { Devices, initDevice } from 'device-decoder'

import { Devices, initDevice } from 'https://cdn.jsdelivr.net/npm/device-decoder@latest'

Getting Started

Provide a configuration object from Devices as the first argument in initDevice to initialize a multithreaded decoding and rendering pipeline.

let info = initDevice(
    Devices['BLE']['hegduino'],

    // Optional settings
    {
        //devices: Devices // A custom device list
        //workerUrl: './stream.worker.js' // Specify a custom worker (using the template at the bottom of this documentation file)
        //reconnect?:true //for USB connections, if usbVendorId and usbProductId are provided and a previous connection was permitted. For BLE provide the deviceId from info.device.deviceId saved from a previous connection. For USB ports use info.device.port.getInfo();
        ondecoded: (data) => console.log(data), //results supplied through codec
        ondata?:(data) => console.log(data), //results direct from device, e.g. bypass codec threads (or use both)
        onconnect: (deviceInfo) => console.log(deviceInfo),
        ondisconnect: (deviceInfo) => console.log(deviceInfo),
        filterSettings: {red:{ useLowPass:true, lowpassHz:50 }, infrared:{ useLowpass:true, lowpassHz:50 }} //IIR Filter settings per output key based on the codec results. See FilterSettings type. sample rate is preprogrammed or can be set in each channel setting
    }
)

Init options:

type InitDeviceOptions = { //you can update ondecoded and ondisconnect at any time
    devices?:{ //defaults to the library internal Device list, which you can add to, but make sure you set a custom worker that loads the list
        [key:string]:{
            [key:string]:any
        }
    },
    
    //this function is required
    ondecoded:((data:any) => void)|{[key:string]:(data:any)=>void}, //a single ondata function or an object with keys corresponding to BLE characteristics
    onconnect?:((device:any) => void),
    beforedisconnect?:((device:any) => void),
    ondisconnect?:((device:any) => void),
    ondata?:((data:DataView) => void), //get direct results, bypass workers (except for serial which is thread-native)
    filterSettings?:{[key:string]:FilterSettings},
    reconnect?:boolean, //this is for the USB codec but you MUST provide the usbProductId and usbVendorId in settings. For BLE it will attempt to reconnect if you provide a deviceId in settings
    roots?:{ //use secondary workers to run processes and report results back to the main thread or other
        [key:string]:WorkerRoute
    },
    workerUrl?:any,
    service?:WorkerService //can load up our own worker service, the library provides a default service
}

Filter settings options (this runs on the thread):

Select a combination of filters, which are preconfigured butterworth IIR filters and a few others:

type FilterSettings = {
  sps:number, //required
  useSMA4?:boolean,
  useNotch50?:boolean,
  useNotch60?:boolean,
  useLowpass?: boolean,
  lowpassHz?:number,
  useBandpass?: boolean,
  bandpassLower?:number,
  bandpassUpper?:number,
  useDCBlock?: boolean,
  DCBresonance?: number,
  useScaling?: boolean,
  scalar?:number,
  trimOutliers?:boolean,
  outlierTolerance?:number
}

I think we can also use the IIR filters in the official Audio API but I have not actually tried, so these are handmade filters ported from an RF tutorial.

The default Devices object is organized as follows:

BLE

• nrf5x: Connect to our [nRF52 microcontroller prototypes] over BLE.
• hegduino: Connect to the HEGduino over BLE.
• cognixionONE: Connect to the Cognixion ONE over BLE.
• statechanger: Connect to the Statechanger HEG over BLE.
• blueberry: Connect to the Blueberry over USB.
• blueberry2: Connect to the Blueberry (v2) over USB.
• heart_rate: Connect to the generic bluetooth heart rate characteristic (compatible with many devices)
• freeEEG16 : Connect to Dmitry Sukhoruchkin's FreeEEG16 module (ESP32 based) over BLE

USB

• nrf5x: Connect to our [nRF52 microcontroller prototypes] over USB.
• freeEEG32: Connect to the FreeEEG32 over USB.
• freeEEG32_optical: Connect to the FreeEEG32 over optical USB.
• freeEEG128: Connect to the FreeEEG128 over USB.
• hegduino: Connect to the HEGduino over USB.
• cyton: Connect to the OpenBCI Cyton over USB.
• cyton_daisy: Connect to the OpenBCI Cyton + Daisy over USB.
• peanut: Connect to the Peanut HEG over USB.
• statechanger: Connect to the Statechanger HEG over USB.
• cognixionONE: Connect to the Cognixion ONE over USB.
• freeEEG16 : Connect to Dmitry Sukhoruchkin's FreeEEG16 module (ESP32 based) over USB

CUSTOM

• simulator: generates sine waves. You can easily modify this protocol.
• webgazer: (via device-decoder.third_party), webcam-based eye tracking via Webgazer.js!

BLE_CUSTOM (under device-decoder.third_party)

• muse: Integrates with the muse-js library.
• ganglion: Modifies the ganglion-ble library. Note, this was broken last time it was tried, but I don't own a ganglion.

Other ideas would be creating media stream drivers to run processes on threads e.g. for audio and video.

These drivers are formatted with simple objects to generalize easily and get the multithreading benefits of device-decoder.

You can create these simple objects to pipe anything through our threading system!

The stream objects returned by initDevice call are structured like the following depending on what type of stream is defined. This gives you full control over your devices on their respective protocols. Note custom defined ones may have arbitrary behaviors.

type SerialDeviceStream = {
    workers:{
        serialworker:WorkerInfo,
        streamworker:WorkerInfo
    },
    options:InitDeviceOptions,
    device:{
        _id:string,
        settings:any,
        info:Partial<SerialPortInfo>
    },
    subscribeStream:(ondata:(data:any) => void) => Promise<any>,
    unsubscribeStream:(sub:number|undefined) => Promise<any>,
    //FYI only works on time series data and on devices with a set sample rate:
    setFilters:(filterSettings:{[key:string]:FilterSettings}, clearFilters?:boolean) => Promise<true>,
    disconnect:()=>void,
    read:()=>Promise<any>,
    write:(command:any)=>Promise<boolean>,
    roots:{[key:string]:WorkerRoute}
};
    

type BLEDeviceStream = {
    workers:{
        streamworker:WorkerInfo
    },
    options:InitDeviceOptions,
    device:BLEDeviceInfo,
    subscribe:(service, notifyCharacteristic, ondata?, bypassWorker?) => Promise<void>,
    unsubscribe:(service, notifyCharacteristic) => Promise<void>,
    //FYI only works on time series data and on devices with a set sample rate:
    setFilters:(filterSettings:{[key:string]:FilterSettings}, clearFilters?:boolean) => Promise<true>,
    disconnect:()=>void,
    read:(command:{ service:string, characteristic:string, ondata?:(data:DataView)=>void, timeout?:TimeoutOptions }) => Promise<DataView>,
    write:(command:{ service:string, characteristic:string, data?:string|number|ArrayBufferLike|DataView|number[], callback?:()=>void, timeout?:TimeoutOptions})=>Promise<void>,
    roots:{[key:string]:WorkerRoute}
};

type CustomDeviceStream = {
    workers:{
        streamworker:WorkerInfo
    },
    device:any,
    options:InitDeviceOptions,
    disconnect:()=>void,
    read:(command?:any)=>any,
    write:(command?:any)=>any,
    //FYI only works on time series data and on devices with a set sample rate:
    setFilters:(filterSettings:{[key:string]:FilterSettings}, clearFilters?:boolean) => Promise<true>,
    roots:{[key:string]:WorkerRoute}
};

Monitoring Multiple Characteristics

For BLE devices with multiple notification or read characteristics, you can supply an object to the ondecoded property in initDevice. This allows you to specify callback functions for each characteristic.

You will need to know which characteristics to specify from the device profile.

const device =  Devices['BLE']['nrf5x']
const services = device.services
let service = Object.keys(services)[0];
let characteristics = Object.keys(services[service]);

let info = initDevice(
    device,

    {
        ondecoded: {
            [characteristics[0]]: (data) => console.log(data),
            [characteristics[1]]: (data) => console.log(data)
        },
    }
)

You may also specify roots in the config object which will subscribe to all outputs from the stream worker thread to be used with graphscript formatting. In the eegnfb example in the GS repo we demonstrated piping multiple workers this way e.g. to run algorithms or build CSV files in IndexedDB.

Stream Worker Template

This is the required base template for our web worker system. You can update the Devices list yourself with your own custom list this way. Otherwise, there is a worker service baked into the library. You can copy that file and our dependencies and work from there, or use the following. Note this is required if you want to customize the device list to take advantage of the multithreaded codec and IIR filters.

import {  WorkerService, workerCanvasRoutes, subprocessRoutes } from 'graphscript'

import { streamWorkerRoutes } from 'device-decoder/src/stream.routes' 

import { Devices } from 'device-decoder/src/devices'

declare var WorkerGlobalScope;

if(typeof WorkerGlobalScope !== 'undefined' && self instanceof WorkerGlobalScope) {

    globalThis.Devices = Devices;

    const worker = new WorkerService({
        roots:{
            ...workerCanvasRoutes,
            ...subprocessRoutes,
            ...streamWorkerRoutes
        }
    });
}

export default self as any; //you can import this as a global in tinybuild to trigger bundling or just add it as an entrypoint to esbuild. 

Contributing

Add your Own Drivers

See docs

[nRF52 microcontroller prototypes]: (https://github.com/joshbrew/nRF52-Biosensing-Boards