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Over 50 devices are advertising

2 years ago

Over 50 devices are advertising

Posted bystanley_yeh0 points 3 replies
0 upvotes

Hi Dialog,
Our client put over 50 devices(DA14585) on his desk, these devices are advertising.
he said it costs too long time (over 15 seconds) to connect to a device.
Then, he took only one device far from other 49 devices and connect to the device, it is fast to make connection.
I think it is normal because there are only 3 channels for advertising, too many devices will disturb the quality of radio, right?

However, he put a previous-generation device(different BLE chip - DA14580, but same adv interval and Tx power) in that 50 devices and try to connect to it.
He said it is still fast to make connection. it fell short of our expectations.
Do you have any idea about the phenomenon?
Thanks a lot.

SDK 6.0.4

2 years ago

PM_Dialog

Hi stanley_yeh,

Let me ask you some question first in order to understand which the problem is and provide you the proper guidelines.

  1. 所有设备一个大学吗que BD address? SDK6.0.10 has an API to get a unique code from OTP and create a static random BDaddress from this.
  2. Are all devices powered-up at exactly the same time? If yes, the RF of one might interfere with the others but if they are randomly enabled they will only occupy a very small timeslot so 50 devices should be able to occupy the same space without problems.
  3. What is the implementation on the scanner/central side?

Thanks, PM_Dialog

2 years ago

stanley_yeh 0 points

Hi PM_Dialog,
1. Yes, all devices are written a unique BD address in OTP by our production line. I am sure all BD addresses are different.
2. I don't think all devices are powered-up at exactly the same time. Is it related to environment? maybe reflected wave? I am sorry I don't know too much about RF.
3. The scanner is a mobile phone. Does the scan interval of host affect something?
Many Thanks!

2 years ago

FvD_Dialog 0 points

你好,

We need to find out if your problem is caused on the central side (Phone) or on the Peripheral side:

  1. The scan interval might impact the behaviour of this. Are you using a generic phone app for this like LightBlue (iOS) or Bluetooth LE Scanner (Android)?
    Did you create your own phone implementation? Can you change the scanning behaviour?
  2. What advertising interval are you using on the peripheral devices?
    To avoid collisions on the RF you should make the ADV interval large enough such that the change of collissions is small. Collisions will happen anyway but the Bluetooth stack will put some randomization on top of the defined ADV interval to avoid the collissions are happening multiple times in a row.

Regards,

FvD_Dialog