问题
I need to know exactly how many packets per interval my BLE can handle. The peripheral, as per its datasheet, handles 6 packets per interval, but I have been unable to find out how many packets the Central can handle. The Central device is a Motorola Moto G (generation 2), running Android 5.0.2.
By examining he btsnoop_hci.log file I have been able to identify multiple connection parameters, such as the connection interval (7.5ms in my case). My questions is wheter it is possible to determine how many packages can be exchanged in a single coonection interval, by examining the negotiation packets in Wireshark.
回答1:
In the spec, there is no negociation about the max number of packets in a Connection Event. A connection event can simply last for at most (ConnectionInterval - 150µs) (See 6.B.4.5.1).
Limitations, if any, are in the PHYs, at either side. Most HCI firmwares limit to 4-5 packets per connection event, per direction.
回答2:
It is up to the controller on the master side to decide how long the connection event should be open (as long there are more packets from any side). The slave has nothing to say about this.
For a central host, when creating a connection as well as when updating connection parameters there are two HCI parameters Minimum_CE_Length and Maximum_CE_Length. These are informational parameters that indicate how long it should keep its connection event open. If these are set to high numbers, the controller will have the connection event open as long as possible.
Sadly, Android set these parameters both to 0 which means most controllers will restrict the connection event to only 3 or 4 packets.
来源：https://stackoverflow.com/questions/36983391/ble-number-of-packet-per-connection-interval-in-wireshark