What is the difference between a BLE central reading from a peripheral versus a peripheral notifying the central in term of resources drained?

[helpme]

Suppose a BLE central needs to get sensor data from 10 peripheral sensors. Given that there is a limit to the number of connections a BLE central can have, is it better for the central to read from peripheral because it uses lesser resources compared to notify?

[Hung Bui]

@helpme: Could you give me more information on why you think read command would use less resource compare to notify ?

As far as I know, sending notify is more efficient than read command when thinking of the number of packet needed to send data (1 packets vs 2 packet).

The only advantage of read command I can think of is that the client (central) doesn't have to wait for notification but has control of when to get it.

[EDITED] Another advantage of using notify is to avoid the delay by slave latency. The peripheral can wake up in the middle of the latency sleeping period to send notification, when with read, the central have to wait until the next wake up of the latency sleeping period to get the data which only comes on next connection event after the read command.

[Hung Bui]

However, it doesn't need to periodically advertising though. How long it would take the peripheral to wake up and start advertise before it can be connected is depend on how the central be configured to do scaning. If the current consumption on the central is not the concern, it can stay in scan mode with big scan window and can have higher chance to catch the advertising packet. I guess in this case helpme hits the constrain on the maximum peripheral can be connected to the central at the same. Currently on S120 we only support 8 connections and on S130 it is 3 for now.