BLE throughput differs between NCS v2.6.0 and v2.9.2.

[chiba]

Hi,

BLE throughput differs between NCS v2.6.0 and v2.9.2.
v2.9.2 appears to have fewer MoreData packets.
(Both have CONFIG_BT_CTLR_SDC_MAX_CONN_EVENT_LEN_DEFAULT set to 7500)

In v2.9.2, I confirmed that setting `CONFIG_BT_CTLR_SDC_MAX_CONN_EVENT_LEN_DEFAULT=15000` changes the number of more data packets.
Is there a difference in how `CONFIG_BT_CTLR_SDC_MAX_CONN_EVENT_LEN_DEFAULT` is handled between v2.6.0 and v2.9.2?

- Using the nrf5340
- Configured for multi-protocol communication with Matter (At the time of this test, commissioning had not been performed, and no Matter communication was taking place)

[Samruddhi Jadhav]

Hello,

Can you please upload your whole application in v2.9.2?

Best Regards,

Samruddhi

[chiba]

HI, I've created a project so you can reproduce it on a DK board.

Overview

Packets are periodically transmitted from the Central to the Peripheral.
Once both devices are powered on, they connect automatically and transmit packets at 1-second intervals.

Project Details

• central_52840dk
  - Description: Central-side project for the nRF52840 DK.
  - Base: ncs292/zephyr/samples/bluetooth/central
• lock_5340dk_ncs260
  - Description: Peripheral-side project for the nRF5340 DK (NCS 2.6.0).
  - Base: ncs260/nrf/samples/matter/lock
• lock_5340dk_ncs292
  - Description: Peripheral-side project for the nRF5340 DK (NCS 2.9.2).
  - Base: ncs292/nrf/samples/matter/lock

8055.lock_5340dk_ncs292.zip

7624.lock_5340dk_ncs260.zip

1856.central_52840dk.zip

[chiba]

HI,

I understand that the state changes with CONFIG_BT_CTLR_SDC_MAX_CONN_EVENT_LEN_DEFAULT.

However, the default value is set to 7500 for both NCS260 and NCS292.

- NCS292:  build\ipc_radio\zephyr\include\generated\zephyr\autoconf.h

- NCS260: build\multiprotocol_rpmsg\zephyr\include\generated\autoconf.h

Why do they behave differently?

[Edvin]

I do see that there have been some changes to the SoftDevice controller regarding the reset state of the softdevice controller between these versions, which probably explains the difference in behavior. 

In v2.9.2 changelog, there is an explicit change:

Extended Connection Events are not re-enabled on HCI Reset; previous state is preserved.

See v2.9.2/nrfxlib/softdevice_controller/CHANGELOG.rst

In v2.6.2 API docs, conn event extend says that after HCI Reset, Extended Connection Events are enabled by default.

Please see these:

https://github.com/nrfconnect/sdk-nrfxlib/blame/v2.9.2/softdevice_controller/CHANGELOG.rst#L100

https://github.com/nrfconnect/sdk-nrfxlib/blob/v2.6.2/softdevice_controller/include/sdc_hci_vs.h#L980

That should explain the difference in behavior. Now that you know how to configure it in v2.9.2, you can tune it to work the way that you want it to work in your application.

Best regards,

Edvin

[chiba]

Hi,

Thanks, I understand now.

To make it behave the same as NCS262, should I just add the following setting?

CONFIG_BT_CTLR_SDC_CONN_EVENT_EXTEND_DEFAULT=y

[Edvin]

Yes, as well as:

CONFIG_BT_CTLR_SDC_MAX_CONN_EVENT_LEN_DEFAULT=20000

[µs] Adjust this one to as long as the maximum amount of time you want the device to spend on the BLE connection. Remember that it will not spend this time unless the other device has data to send. But if the connected device has a lot of data, it may spend up to this amount of µs for BLE on every connection interval (meaning this amount of time will not be spent on Matter/Thread).

Best regards,

Edvin

[chiba]

Hi,

I understand the description of CONFIG_BT_CTLR_SDC_MAX_CONN_EVENT_LEN_DEFAULT.

I would like to know how to configure it so that it behaves the same as lock_5340dk_ncs260.

For lock_5340dk_ncs260 and lock_5340dk_ncs292, CONFIG_BT_CTLR_SDC_MAX_CONN_EVENT_LEN_DEFAULT is set to 7500.

To make lock_5340dk_ncs292 behave the same as lock_5340dk_ncs260, should it be changed to 2000?