NRF52840 slow bluetooth transmission speeds (2M, CODED) after SDK update (14.2->15.2)

[Daniel]

Hi,

I got a working app, based on app_template with custom bluetooth services which transfer raw (simulated) data from nRF52840 DK to my Andoid App.

This app worked fine until I updated my Nordic SDK from 14.2. to 15.2.

I updated all required methods and librarys, so that my app works as inteded except the transfer speed.

Before I got transferspeeds in 2M mode about 1300 kbps, now is the highest speed I reach about 350kbps.

I already changed the default parameters of gap data length to 251, MTU to 247, but still got no solution for this problem.

Some functions are based of ble_app_att_mtu_throughput and nrf52-ble-image-transfer-demo-master. I compared these apps with mine, but found no differences.

Maybe someone got some other ideas.

Greetings,

Daniel

[Sigurd]

Hi,

Try setting NRF_SDH_BLE_GAP_DATA_LENGTH in sdk_config.h to 251

[Daniel]

I already set NRF_SDH_BLE_GAP_DATA_LENGTH and NRF_SDH_BLE_GATT_MAX_MTU_SIZE to highest possible. 251 and 247.

[Sigurd]

Ok, try setting NRF_SDH_BLE_GAP_EVENT_LENGTH to 400

[Daniel]

Okay I changed it from 6 to 400, but nothing changes. I took a look into my 14.2. project, there was the Event_Length set to 320.

Do I need to change the config to allow 400 manually?

Like here: devzone.nordicsemi.com/.../setting-gap-connection-event-length---ble-hrs-c-demo

[Sigurd]

320 should be good.

1) Are you sure that you are on 2M PHY ? How are you verifying that?

2) Any chanes to the connection interval?

3) Are you testing against the same Android phone you got 1300 kbps with ?