DFU - SDK 14.1.0 - Support for higher MTUs added.

[schef]

Hello, I'm reading on github.com/.../Android-DFU-Library that there is a support for higher MTU on DFU. Is there an example how i should test it?

I'm tring to increase MTU on examples/dfu/bootloader_secure_ble/ but nothing much changes.

It is doing something like step by step and wait procedure.

[Hung Bui]

Hi Schef,

I don't think longer MTU size is supported on the DFU firmware on SDK v14.1

But you can try to increase it, simply increase NRF_SDH_BLE_GATT_MAX_MTU_SIZE to 247 as in our \ble_central_and_peripheral\experimental\ble_app_att_mtu_throughput example.

You can follow the example to see how you can increase the throughput on DFU.

Note that increasing MTU wouldn't improve through put significantly. Because it's only save some header bytes. The packet on air under L2CAP stays the same.

What can improve through put more significantly is Data length extension. But I don't think it can be handled from the app. The phone OS controls that. Also, note that not all the phones support all BLE 4.2 or v5.0 features.

[schef]

Isnt Data length extension same as using NRF_SDH_BLE_GATT_MAX_MTU_SIZE 247?

[Hung Bui]

No, they are not the same. Have a look here.

[schef]

I have some problems with gatt. The function calls (void) nrf_ble_gatt_data_length_set(&m_gatt, BLE_CONN_HANDLE_INVALID, data_length); but there is no &m_gatt in nrf_ble_dfu.c.

[Hung Bui]

Can't you just create one ? If you look in main.c of the throughput example you can find m_gatt is init in gatt_init().

To be able to verify that data length extension and large ATT MTU is working, I would suggest you to use a sniffer to capture the communication. Or at least monitor the events and check if the request actually works.