BLE Connection Interval

[BEN_HB]

Hi.

setup is 52832, SDK15.3.0, S332

I set MIn Max connection inverval is 500ms.

when connect using nRF Connect app, it is not change immediately connection inverval to 500ms.

7.5ms -> 45ms -> 500ms. why does not connect first interval to 500ms?

first connection interval (7.5ms) currnet power is raise to high and change 45ms -> 500ms , down normal.

I wanna remove first connect about raise current power.

Is it possible?

Thank you

[Sigurd]

Hi,

BEN_HB said:

Is it possible?

No.

It's the BLE central/master that sets initial connection interval, as part of the CONNECT_IND packet (interval field).

This is usually set relativity low, in order to reduce the time e.g. the service discovery takes. So in most cases a 7.5ms initial connection interval is preferred. The slave can after the initial connection send a Connection Parameter Update Request packet to request the interval to be changed.

[BEN_HB]

Thanks. got it.

about 45ms?

in nrf connect log, connected -> 7.5ms -> services discovery -> 45ms -> 500ms

is it possible remove 45ms?

[Sigurd]

How long time is it between the changes ?

When did it switch to 45ms ?

When did it switch to 500ms ?

If you don't have the timestamps in nRF Connect app, then you could use nRF Sniffer to see the timing.

[BEN_HB]

here is log of connect app

I removed some log regardless them

V 12:16:55.733 Connecting to ########
D 12:16:55.733 gatt = device.connectGatt(autoConnect = false, TRANSPORT_LE, preferred PHY = LE 1M)
D 12:16:56.317 [Callback] Connection state changed with status: 0 and new state: CONNECTED (2)
I 12:16:56.317 Connected to ##########
V 12:16:56.338 Discovering services...
D 12:16:56.338 gatt.discoverServices()
D 12:16:56.364 [Broadcast] Action received: android.bluetooth.device.action.ACL_CONNECTED
I 12:16:56.760 Connection parameters updated (interval: 7.5ms, latency: 0, timeout: 5000ms)
D 12:16:57.243 [Callback] Services discovered with status: 0
I 12:16:57.243 Services discovered
V 12:16:57.273 Generic Access (0x1800)
I 12:16:57.342 Connection parameters updated (interval: 45.0ms, latency: 0, timeout: 5000ms)
I 12:16:58.297 Connection parameters updated (interval: 500.0ms, latency: 0, timeout: 4000ms)

where is 45ms updated? I thought I didn't set 45ms, only 500ms.

thank you

[Sigurd]

BEN_HB said:

where is 45ms updated?

Most likely the phone/central that decided this(A sniffer log would show this) after the service discovery was finished. But looking at these timestamps, it only takes 2 seconds after initial connection before it switched to 500ms. So I don't see any issues with this log.