Break up large ArrayBuffer before writing to BLE characteristic

index.js

// Mock BLE so you can run example from nodejs
const ble = {
    write: function(device_id, service, characteristic, buffer, success, failure) {
        // log to console instead of writing
        console.log('>>', new Uint8Array(buffer));
        // always call success callback
        success();
    }
}

// fake device and service
const device_id = 'aa:bb:cc:dd:ee:ff';
const service_uuid = 'AAA0';
const characteristic_uuid = 'AAA1';

const MAX_DATA_SEND_SIZE = 20;

// write large ArrayBuffer by breaking into smaller chunks
function writeLargeData(buffer) {
    console.log('writeLargeData', buffer.byteLength, 'bytes in',MAX_DATA_SEND_SIZE, 'byte chunks.');
    var chunkCount = Math.ceil(buffer.byteLength / MAX_DATA_SEND_SIZE);
    var chunkTotal = chunkCount;
    var index = 0;
    var startTime = new Date();

    var transferComplete = function () {
        console.log("Transfer Complete");
    }

    var sendChunk = function () {
        if (!chunkCount) {
            transferComplete();
            return; // so we don't send an empty buffer
        }

        console.log('Sending data chunk', chunkCount + '.');

        var chunk = buffer.slice(index, index + MAX_DATA_SEND_SIZE);
        index += MAX_DATA_SEND_SIZE;
        chunkCount--;

        ble.write(
            device_id, 
            service_uuid, 
            characteristic_uuid, 
            chunk, 
            sendChunk,         // success callback - call sendChunk() (recursive)
            function(reason) { // error callback
                console.log('Write failed ' + reason);
            }
        )
    }
    // send the first chunk
    sendChunk();
}

// Generate some fake data
const data = new Uint8Array(50);
for (let i = 0; i < 50; i++){
    data[i] = i;
}
writeLargeData(data.buffer);        

THANK YOU. BLE LIMIT 20 SUCCESS