Android 5.01 (Nexus 4) multiple packets per connection interval

[Matthias]

Dear community,

I would like to know how to send as much data as possilbe from a Nexus 4 to an NRF51822 based device. For that I think I need to send multiple packets per connection interval.

What I did:

I searched the interwebs and also this community. ;) and found this: devzone.nordicsemi.com/.../

I set the connection interval to:

In the Sniffer I see that the devices agree to about 10 ms which is fine:

To send Data I use a queue and the onCharacteristicsWrite callback to pump data in 20 byte chunks to the device:

public void writeCharacteristicBulk()
{
    BluetoothGattService service = mBluetoothGatt.getService(UUID.fromString("xxx"));
    BluetoothGattCharacteristic bluetoothGattCharacteristicA = service.getCharacteristic(UUID.fromString("xxx"));
    byte[] value;
    boolean status;

    bluetoothGattCharacteristicA.setWriteType(BluetoothGattCharacteristic.WRITE_TYPE_NO_RESPONSE);
     value = mDataToTransfer.poll();
    if(value!=null) {
        bluetoothGattCharacteristicA.setValue(value);
        status = mBluetoothGatt.writeCharacteristic(bluetoothGattCharacteristicA);
        Log.d(TAG, "write " + bluetoothGattCharacteristicA.getUuid() + " status " + status);
    }
}

and later ...

 @Override
        public void onCharacteristicWrite(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic, int status) {
            writeCharacteristicBulk();
        }

But when I send large amounts of data (96 packets of 20 byte) I only see one per interval in the sniffer:

So the question is: Is it possible to send more than that? Or is the throughput calculation of the above mentioned question only valid for android receiving data?

Thanks and have a great weekend Matthias

[Gerard]

Hi Matthias,

See https://devzone.nordicsemi.com/question/5121/send-multiple-notifications-per-connection-interval/

The sniffer will support only one packet per interval, so you can't really use this for throughput testing.

[Matthias]

Hello Gerard, thank you for this information. I had a look at the link you provided. I don't use the dongle as part of the connection but as sniffer only and I have seen traces of the sniffer having several packets per connection interval. I think in this very post there is a screen shot of just that. So thank you for sharing, but I tink the sniffer does actually support multiple packets. So the actual qoute would be:

You should note that the current master emulator dongle will support only one packet per interval, so you can't really use this for throughput testing

[Stefan Birnir Sverrisson]

@Gerard: I think the master emulator firmware v0.9 had a limitation of 1 packet per connection interval. The master emulator firmware v0.10 and later can however handle up to 6 packets per connection interval and 7.5ms connection interval.

[Stefan Birnir Sverrisson]

HI Matthias

Nexus 4 seems to support 1 packet per connection interval TX, i.e. central to peripheral, but 4 packets per connection interval RX. So your observation seems to be as expected.