Central (9) and Peripheral connections(1- mobile) - baseband scheduling

RE: Central (9) and Peripheral connections(1- mobile) - baseband scheduling

Hung Bui — Tue, 19 Apr 2022 12:35:30 GMT

Great, thanks for letting us know :) I'm happy that it works now.

RE: Central (9) and Peripheral connections(1- mobile) - baseband scheduling

Abishek — Tue, 19 Apr 2022 08:33:40 GMT

Thank you Hung Bui, Its working for us.

The problem is with the GAP interval , data packet size and connection interval usage.

Now we have full control over the data flow and the latency and the tunning values.

RE: Central (9) and Peripheral connections(1- mobile) - baseband scheduling

Hung Bui — Thu, 31 Mar 2022 08:19:04 GMT

Hi Abishek,

I would suggest to have a look at section 15.2 Initiator timing in the S140 specification. In the section, we discussed about the algorithm of scheduling.
Basically the central will try to put the new connection in a "best-fit" free time space that doesn't collide with other connection events. And it works best if they all have the same connection interval.

There is prioritization when you establish a new connection. However, when a connection has its connection event skipped for several time, it will have higher priority than other connections.

It's very important that the connection event length is configured small enough so that all 7+1 connection event can be scheduled inside the 40ms interval. If they are above 5ms there will be collision. I would suggest to test with 2.5ms.

RE: Central (9) and Peripheral connections(1- mobile) - baseband scheduling

Abishek — Thu, 31 Mar 2022 06:57:03 GMT

Hi Hung Bui, thanks for the valuable reply.

The connection interval used is 30ms between Nodes and Central. (all connections)

Could you please clarify one doubt:

Assume we got 1+7 connections in the central node. (Mobile and 7 Sensor nodes).

All connection interval is forced to 40ms, will it arrange the connection in free slots, like 0,5,10,....40,45,50...,80,85,90.. with 5ms event length.

or Do we have special priority for central and peripheral connections in the baseband? Is there any best connection interval, which works better for the 1+7 device and scheduler?

Yes, we will try the there things mentioned

.1) Sniffer

2)Connection Event

3)Disable time_sync

thank you,

Abishek

RE: Central (9) and Peripheral connections(1- mobile) - baseband scheduling

Hung Bui — Wed, 30 Mar 2022 13:32:17 GMT

Hi Abishek,

A sniffer trace is critical to debug this issue. If you don't have a dedicated sniffer you can use one of our nRF52 DK as the sniffer. Please download the sniffer here. It won't be able to track the connection of all 10 peripheral and one phone but you can track one connection at a time and still it can provide a lot more insight.

Please provide the information on:

- Which interval have you configured between the central and the sensor. You mentioned " 30ms(min 24 units) to 150ms and it always takes 30 ms as a connection interval between nodes and mobile." but it's not clear to me what's the connection interval between the central and the sensors.

- Please check the event length configuration for each connection. They should be as small as possible matching with the amount of data transferring. Here is an example in the S140 SDS

- Please try to turn off the time_sync feature to test, just to make sure it's not the timeslot that messing up the connection events. From what I know about the time_sync example the receiver will always stay in timeslot and scanning on the radio. So it's active all the time (when the softdevice is not doing any BLE), not just once in 5 seconds. If you configure the timeslot at low priority it should be fine, but it worth it to test to double check.