我可以使用 chrome web 蓝牙低能量 android 将来自树莓派的图像的 stream 发送到 android 吗？

Question

Currently I have a HTML/Javascript web application working on my Android that can pair with a raspberry pi using the Chrome web bluetooth api. I understand that up to 512 bytes can be sent through a GATT characteristic which is too small for my purposes. Is there a way to send a stream of images (or even just one image for now) from the pi to my android over BLE with this web bluetooth api?

Here is the javascript code to request the raspberry pi below. I have python scripts running on the pi to advertise itself and its services/characteristics. Currently I have a custom GATT characteristic that I have built but can't send an image through because of the 512 byte limit. After using the API to find/connect to the pi, is there another way to send images from the pi back to the android?

    //device and characteristic variables

    var bluetoothDevice;

    var imageCharacteristic;



    //decoder for array buffer -> string

    var enc = new TextDecoder("utf-8");



    //UUIDs

    //service uuid 

    const serviceUUID = '00000001-710e-4a5b-8d75-3e5b444bc3cf'


    //write characteristic for taking an image on the pi

    const imageCharacteristicUUID = '00000007-710e-4a5b-8d75-3e5b444bc3cf'



    //button 1: change connect/disconnect button when clicked

    connectButton.addEventListener('click', function handleClick() {

        const initialText = 'Connect';



        if (connectButton.innerText.includes(initialText)) { //user clicks 'connect'

            //check if see if bluetooth device has already been requested

            return (bluetoothDevice ? Promise.resolve() : requestDevice())

            .then(connectDevice)

            .then(_ => {

                connectButton.innerText = 'Disconnect';

                document.getElementById("status").innerHTML = 'BT Connected';

            })

            .catch(error => {

                console.log('error' + error);

            });

        } else { //user clicks 'disconnect'

            if (bluetoothDevice.gatt.connected) { //error handling to ensure device is actually connected

                console.log('disconnecting...')

                bluetoothDevice.gatt.disconnect();

            } else {

                console.log('Bluetooth Device is already disconnected');

            }

        }

    })



    //request device using web bluetooth api

    function requestDevice() {

        return navigator.bluetooth.requestDevice({

            //filter to search for one device

            filters: [

                {name: 'rasPi'},

                {services: [serviceUUID]}

            ]

        })

        .then(device => {

            bluetoothDevice = device;

        })

    }



    //connect to device and register services and characteristics

    function connectDevice() {

        if (bluetoothDevice.gatt.connected) {

            return Promise.resolve();

        }

        console.log("connected");

        return bluetoothDevice.gatt.connect()

        .then(server => server.getPrimaryService(serviceUUID))

        .then(service => service.getCharacteristics())

        .then(characteristics => {

            //start a queue to gather each characteristic

            let queue = Promise.resolve();

            characteristics.forEach(characteristic => {

                switch (characteristic.uuid) {

                    case BluetoothUUID.getCharacteristic(imageCharacteristicUUID) :

                        queue = queue.then(_ => {

                            imageCharacteristic = characteristic;

                        })

                        break;

                    default : console.log('Unknown Characteristic: ' + characteristic.uuid);

                }

            });

            return queue;

        })

    }

Answer 1

Resolved: I ended up converting the image to a string and sending it through one characteristic with a loop. My web page starts characteristic notifications and gets 512 bytes at a time to then string together and display an image.