How can i increase throughput

[T_chapelle]

Hi all !

I'm trying to evaluate the throughput i can have between a Motorola 4G and the nrf51. The nRF51 is the peripheral and the phone is acting as a central.

To do that, i've based my work on the nRFToolbox android source code and modified the uart example. It read a file and send it by chunk of 20 bytes to the BLE peripheral by writing to the characteristic with the functions "mRXCharacteristic.setValue(data);" and "writeCharacteristic(mRXCharacteristic);"

On the nRF51, i've modified the peripheral uart example as well. I use the SD130v2 with SDK11. It gather the 20 bytes messages and send them to the uart using the "nus_data_handler()"

So far, i've tested different files size and succeed on getting a data rate of 1.25kbps with packet ack and 2.5 kbps without it (setWriteType(WRITE_TYPE_NO_RESPONSE) on android) and by lowering the connexion interval to 7.5ms.

After reading

devzone.nordicsemi.com/.../ devzone.nordicsemi.com/.../ devzone.nordicsemi.com/.../how-can-i-improve-throughput-for-ble-link

, i think i understand that i can achieve better data rate by increasing the packets sent per connection event.

...But i can't find a way to do so on the android side. Can you please give me hints or guidance to send multiple packets per connection even ? Also, i don't want to use a large write :-)

Thank you !

[T_chapelle]

Strange... because doing the same, i have the following log for 20 characters :

V 11:38:31.544 Writing characteristic 6e400002-b5a3-f393-e0a9-e50e24dcca9e (WRITE REQUEST) D 11:38:31.553 gatt.writeCharacteristic(6e400002-b5a3-f393-e0a9-e50e24dcca9e) I 11:38:31.703 Data written to 6e400002-b5a3-f393-e0a9-e50e24dcca9e, value: (0x) 61-62-63-64-65-66-67-68-69-6A-6B-6C-6D-6E-6F-70-71-72-73-74 A 11:38:31.710 "abcdefghijklmnopqrst" sent

And this for 21 bytes :

V 11:38:37.281 Writing characteristic 6e400002-b5a3-f393-e0a9-e50e24dcca9e (WRITE REQUEST) D 11:38:37.299 gatt.writeCharacteristic(6e400002-b5a3-f393-e0a9-e50e24dcca9e) E 11:39:07.323 Error (0x85): GATT ERROR V 11:39:07.584 Disconnecting... D 11:39:07.592 gatt.disconnect() D 11:39:07.689 [Callback] Connection state changed with status: 22 and new state: 0 (DISCONNECTED) D 11:39:07.694 Activity disconnected from the service W 11:39:07.698 Error: (0x16): GATT CONN TERMINATE LOCAL HOST

Also i should precise that i tried it with default binaries and with two phones! (ble_app_uart_s130_pca10028.hex and toolbox from playstore)

[Jorge]

I'll try to see if I changed something from the uart example, because It was a long time ago that I started to use it, and i changed a lot of things for my project. If I discover something I'll update this.

I was moving through my code and the code from the example of peripheral UART and I think I didn't change any size. The #define BLE_NUS_MAX_DATA_LEN (GATT_MTU_SIZE_DEFAULT - 3) which = 20. Maybe the problem is that your phone just allow one connection. Sorry for not being able to help you with this. Maybe someone else will have a better answer for this

[Anders Strand]

Do you have another nRF51 device you can set up as a nRF Sniffer?. If you set set connection interval to something high like 2 seconds, you can easily see how many packets are sent each connection interval. I have achieved at least 4 packets/interval with the nRF uart app doing this. (It might have been 6 packets, i dont remember)

[Anders Strand]

I see from your new comment that you are sending WRITE REQUEST from the Android. This requires the peripheral to respond to the request (in application) before the next packet is sent. This will lead to 1 packet/interval. Use Write commands (or whatever it is called in Android) instead. That is, writes which are not requests.

[T_chapelle]

Saddly , i don't have a Sniffer :-( I don't use WRITE REQUEST on my code, the log i showed you was with the default binaries provided by Nordic. In the code i modified, i can see the WRITE COMMAND on the log, due to the function setWriteType(WRITE_TYPE_NO_RESPONSE) in android.