Connection parameter optimize: nRF52840(central) multilink with 8x52832 peripherals

RE: Connection parameter optimize: nRF52840(central) multilink with 8x52832 peripherals

Sigurd — Thu, 10 Oct 2024 08:18:32 GMT

With NRF_SDH_BLE_GAP_EVENT_LENGTH=3 (in 1.25ms units), you have 8*3,75 = 30ms, then you have the scanner on top of that.

NRF_BLE_SCAN_SCAN_WINDOW = 16 (in 0.625 ms units) -> 10ms , with tScanReserved ~1ms, you should have a connection interval of at least 41ms when you have 8 connections running + the scanner running.

RE: Connection parameter optimize: nRF52840(central) multilink with 8x52832 peripherals

Avadacadabara — Wed, 07 Aug 2024 06:51:24 GMT

Plus following snippet is current scan parameters on my Central, is there any conflicts between connection event and scanning event?

RE: Connection parameter optimize: nRF52840(central) multilink with 8x52832 peripherals

Avadacadabara — Wed, 07 Aug 2024 06:50:07 GMT

Hi,

I tried to set Central GAP_EVENT_LENGTH to 3 but seems like the disconnection is getting worse. Then I set both Central and Peripheral GAP_EVENT_LENGTH to 24 and it could hold connection quite a long time in range of 2 meters. But when I try to move further (3m), they could still hold for several minutes. Then first come the throughput unstablization, followed with massive disconnection and reconnection.

I've already turn on DLE for all Central and peripherals.

[quote userid="15146" url="~/f/nordic-q-a/113706/connection-parameter-optimize-nrf52840-central-multilink-with-8x52832-peripherals/497149"]PS: Connection Event Length Extension could also be helpful for the throughput:[/quote]

RE: Connection parameter optimize: nRF52840(central) multilink with 8x52832 peripherals

Sigurd — Tue, 06 Aug 2024 12:03:52 GMT

[quote user="Avadacadabara"]Then should I remain Peripherals to 6 or change them to 24(which equals to 30ms)?[/quote]

If the peripherals only connect to 1 central, then you could increase it to 24.

PS: Connection Event Length Extension could also be helpful for the throughput:

https://infocenter.nordicsemi.com/topic/sds_s140/SDS/s1xx/multilink_scheduling/extend_connection_event.html

    ble_opt_t  opt;

    memset(&opt, 0x00, sizeof(opt));
    opt.common_opt.conn_evt_ext.enable = 1;

    err_code = sd_ble_opt_set(BLE_COMMON_OPT_CONN_EVT_EXT, &opt);
    APP_ERROR_CHECK(err_code);

RE: Connection parameter optimize: nRF52840(central) multilink with 8x52832 peripherals

Avadacadabara — Tue, 06 Aug 2024 11:40:37 GMT

Peripherals are set to 6(7.5ms) and Central is set to 80.

[quote userid="15146" url="~/f/nordic-q-a/113706/connection-parameter-optimize-nrf52840-central-multilink-with-8x52832-peripherals/497137"]Do you have NRF_SDH_BLE_GAP_EVENT_LENGTH set to 80 on the central as well ?[/quote]

So you were saying I should set Central NRF_SDH_BLE_GAP_EVENT_LENGTH to 3. Then should I remain Peripherals to 6 or change them to 24(which equals to 30ms)?

RE: Connection parameter optimize: nRF52840(central) multilink with 8x52832 peripherals

Sigurd — Tue, 06 Aug 2024 11:31:46 GMT

Hi!

Do you have NRF_SDH_BLE_GAP_EVENT_LENGTH set to 80 on the central as well ?

If you have a connection interval of 30ms, and 8 links, try setting it to 30/8= 3.75 ms. It's in 1.25 ms units, so 3,75/1,25=3

so try to set NRF_SDH_BLE_GAP_EVENT_LENGTH to 3 on the central's sdk_config.h, and see if the behavior changes.

See this link for more info: https://infocenter.nordicsemi.com/topic/sds_s140/SDS/s1xx/multilink_scheduling/suggested_intervals_windows_s132.html

RE: Connection parameter optimize: nRF52840(central) multilink with 8x52832 peripherals

Avadacadabara — Tue, 06 Aug 2024 10:57:37 GMT

Hi，

Yes I tried the same setting on 52840 DK, 52840 dongle and custome board.

[quote userid="15146" url="~/f/nordic-q-a/113706/connection-parameter-optimize-nrf52840-central-multilink-with-8x52832-peripherals/497128"]1) Are you testing this with custom board or DK ? If you are using custom board, do you see the same behavior with nRF52840-DK?[/quote]

Current GAP_EVENT_LENGTH is 80(this is for 80ms connection interval condition I previous set, and remain untouched when change to 30ms interval).

[quote userid="15146" url="~/f/nordic-q-a/113706/connection-parameter-optimize-nrf52840-central-multilink-with-8x52832-peripherals/497128"]2) What is your NRF_SDH_BLE_GAP_EVENT_LENGTH value in sdk_config.h?[/quote]

If TOTAL_LINK_CNT is set to 1 then it won't happen. This only happens in multilink applications.

[quote userid="15146" url="~/f/nordic-q-a/113706/connection-parameter-optimize-nrf52840-central-multilink-with-8x52832-peripherals/497128"]Does this happen when there are only 1 device connected? or do you need to connect all 8 peripherals for this to happen?[/quote]

RE: Connection parameter optimize: nRF52840(central) multilink with 8x52832 peripherals

Sigurd — Tue, 06 Aug 2024 10:45:36 GMT

Hi!

1) Are you testing this with custom board or DK ? If you are using custom board, do you see the same behavior with nRF52840-DK?

2) What is your NRF_SDH_BLE_GAP_EVENT_LENGTH value in sdk_config.h?

[quote user=""]stability seems very sensitive to distance. [/quote]

Does this happen when there are only 1 device connected? or do you need to connect all 8 peripherals for this to happen?