Ebyte E104-BT5011A, Руководство пользователя

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2. Precautions for use
2.1 BLE description
This section briefly introduces BLE related knowledge. It has nothing to do with the module.
2.1.1 Connection gap, broadcast gap, scan gap
In order to ensure low power consumption, BLE adopts intermittent working mode.
The scanning interval means scanning the broadcast channel every certain time. The smaller the scan gap, the higher
the average power consumption during the scan, but the faster the slave device is found, and vice versa.
The broadcast interval is to publish a broadcast every certain time. The smaller the broadcast gap, the easier it is for
the slave device to be discovered by the master, and the higher the average power consumption.
For connected BLE devices, the master initiates a request to the slave every certain time (connection gap), and after
receiving the request, the slave responds to the master's request at the same time (connection gap). If the slave does not
respond to the master request within the specified time (connection timeout), the master judges that the slave is
disconnected, and the slave fails to receive the request from the master within the specified time (connection timeout),
the slave judges that the master is disconnected connection. In order to reduce BLE power consumption again, the BLE
protocol also stipulates that the slave can ignore the specified number of requests (slave timeout).
The smaller the connection gap, the greater the data throughput, but the greater the power consumption. If users are
concerned about data throughput, the connection gap can be reduced.
Note that for the connection gap, the connection gap may be different for different devices, or even cannot be
changed, such as iphone.
2.1.2 MTU
It refers to the effective size of BLE air single packet data. The MTU of the ble4.0/4.1 protocol is 27 bytes, and the
MTU can be expanded to 251 bytes from ble4.2 and higher.
When the MTU is actually used, how can the user's effective minus be reduced by 3 bytes of the header. This means
that the maximum single packet data for 4.0/4.1 users is 24 bytes, and the maximum single packet data for ble4.2 and
higher is 247 bytes.