Transfer speed secure DFU SDK14

[janR]

Hi,

I wonder what transfer speed can be expected on a BLE DFU update on a nRF52832 based device in the following condition?

-SDK14.0 Secure DFU, nRF52832, Android tablet (Oreo, Bluetooth 5.0), nRF Connect

We are currently facing a transfer speed of about 1 Kbytes/sec, which sounds way too low. On a 350 Kbytes file, it will take almost 6 minutes to transfer.

Regards, Jan

[janR]

Hi,

I have now managed to improve speed of the secure DFU bootloader in SDK14.
Speed has improved from about 1 kbyte/sec to 3.5 kbyte sec on a Samsung tablet with bluetooth 4.2, and about 5.5 kbyte/sec on a Samsung Galaxy S8 phone with bluetooth 5.
The only change to bootloader is reducing connection interval. This is now reduced from 48.75ms to between 10 and 12ms.
There were no functionality in the SDK14 secure DFU bootloader for doing this (no negotiation were done regarding connection interval), so tablet could set whatever connection interval it wanted.
In SDK11, (which has much faster flashing) the negotiation was implemented using the ble_conn_params module.
Enabling the NRF_BLE_CONN_PARAMS in SDK14, setting min/max connection interval to 10/12, and call the ble_conn_params_init() did the trick.

Regards, Jan