BLE: sending data to device

[i.n.g.o.]

Hello.

i'm asking myself if this is the way to send data to a BLE device:

void BLESerialDevice::writeData(const QByteArray& data) {

    // get 20 bytes (?) to send
    dataSending = data.left(20);
    dataLeftToSend = data.right(data.size()-20);

    m_service->writeCharacteristic(writeCharacteristic, dataSending, QLowEnergyService::WriteWithResponse);
}

void BLESerialDevice::mycharacteristicWritten(const QLowEnergyCharacteristic &info, const QByteArray &value) {
    // checks removed (compare value to dataSending, etc)

    // write next 20 bytes
    writeData(dataLeftToSend);
}

...

// get data and write it out
void doSendData() {
    QByteArray data = getSomeData();
    MyBLESerialDevice.writeData(data);
}

sending data with this method transmits all the bytes, only the data-rate if pretty low:

sent  2429 bytes  in  9243  ms  =  ~263 bytes per seconds

trying to send it in a tight loop would drop data...

void BLESerialDevice::writeData(const QByteArray& data) {
    int i = 0;
    while (true) {
        dataSending = data.mid(i, 20);

        if (dataSending.isEmpty()) break;

        m_service->writeCharacteristic(writeCharacteristic, dataSending, QLowEnergyService::WriteWithResponse); 

        i += 20;
    };
}

so i wonder:
is this (first code-snippet) the way to send data to a BLE device?
how would the preferred way to write data be?
how could the data-rate be improved?

thanks for comments and recommendations
io

[J.Hilk]

@i.n.g.o.
Hi, the First version is, roughly, the way I do it currently too. You‘re actually faster, because I‘m bound to a Modbus type of protocol that take 8 byte away for a head and Tail.
😔

[kuzulis]

BLE is not designed to fast data transferring.

PS: Also many things depends on type of your remote device: who did FW (maybe it has bugs or sleeps), what is a characteristic's properties, what is a HW vendor (TI, NORDIC and etc).

[i.n.g.o.]

thanks for the comments!