SYD8801 is a low-power high-performance Bluetooth low-power SOC that integrates high-performance 2.4GHz radio frequency transceiver, 32-bit ARM Cortex-M0 processor, 128kB Flash memory, and rich digital interfaces. SYD8801 integrates Balun on-chip without impedance matching network, high-efficiency DCDC step-down converter, suitable for wearable, Internet of Things devices, etc. For details, please consult: http://www.sydtek.com/
Ask about the size of the Bluetooth data packet
In the section "2 AIR INTERFACE PACKETS" of the 4.0 Bluetooth specification, the structure of the BLE Bluetooth link layer data packet is defined as follows:
It is stipulated that the maximum size of the PUD is 39 bytes. Here to analyze the PUD size of the data channel, let's look at the following definition:
And the following explanation about the length of the payload Length:
This means that the maximum payload length is 27 bytes!
Later, the definition of l2cap is as follows:
4 bytes are subtracted here, so the real upper data size is only 23 bytes!
For notified, the definition in att is as follows:
3 bytes are subtracted here, so the effective data size for notify is 20 bytes
Upload the Bluetooth 4.0 specification here: http://download.csdn.net/detail/chengdong1314/9780390
WAS PACKED FORMAT
Preamble
Advertising channel packetsshall have 10101010b as the preamble.
The data channel packetpreambleis either 10101010b or 01010101b, depending on the LSB of the AccessAddress. If the LSB of the Access Address is 1, the preamble shall be01010101b,otherwise the preamble shall be 10101010b.
AccessAddress
The Access Address for all advertising channel packets shall be 0x8E89BED6.
The Access Address in data channel packets shall be different foreach Link Layer connection between any two devices with certain restrictionsasdefined .
ADVERTISINGCHANNEL PDU
Header field
PDU Type
TxAdd andRxAdd
The TxAdd and RxAdd fields of the advertising channel PDU that arecontained in the header contain information specific to the PDU type definedfor each advertising channel PDU separately. If the TxAdd orRxAdd fields arenot defined as used in a given PDU then they shall be considered Reserved for FutureUse.
DATA CHANNEL PDU
