What changes did Bluetooth 5.2 bring?

Bluetooth 5.2 increases the function of low-power synchronous channel, supports LE audio, and improves this short-range wireless standard. Let's talk about the specific changes of Bluetooth 5.2.

1, low-power Bluetooth synchronization channel

The low-power Bluetooth synchronization channel function is very important to support LE Audio, because it allows time-limited data to be transmitted to one or more devices for time synchronization. This technology expands the application of audio, because it can not only be used for one-to-one connection, but also broadcast to multiple devices through connectionless topology.

Advanced Audio Distribution Mode (A2DP) is an existing Bluetooth audio mode, which defines how to use Bluetooth for high-quality audio applications, such as transferring music from a smartphone to a set of Bluetooth headsets. The disadvantage of A2DP is that it can only support single or multiple peer-to-peer pairing topologies, which define the relationship between "playing source" (such as playing devices such as smart phones) and "receiving devices" (such as speakers playing sounds). A2DP can't guarantee that multiple receivers can play audio streams accurately at the same time, so it's difficult to achieve synchronous playback on a series of related devices. In fact, Bluetooth audio devices using A2DP can only work when connected to a single device.

Low-power synchronous channel provides a mechanism to overcome this shortcoming, which can ensure that multiple receiving devices (such as left and right headphones) receiving data from the same source can play at the same time. Data has a time-limited validity period and expires after the end of this period. Expired data that has not been sent will be discarded. These mechanisms can ensure that the receiving device only receives valid data that meets the waiting time and delay rules.

2. Synchronization channel has achieved many new applications.

With the new low-power synchronous channel function, many new usage methods, new topological structures and finally many new products will be realized. The function of using low-power Bluetooth as audio is called music audio. The most obvious example of music audio scene is personal audio sharing. A group of friends can use their own Bluetooth headsets and enjoy music played on their smartphones at the same time. This is an example of a private group sharing an audio source. The application of this sound situation in teaching and teaching environment can be said to be varied. For example, individuals and groups grouped in a lecture hall or industrial production line can hear the same content, the same explanation and teaching content at the same time.

A similar example is "public hearing aid", that is, the dialogue broadcast of theater performances, which can be clearly heard by users who use low-power Bluetooth hearing AIDS in the audience. For example, the same technology can also be applied to the TV in the gym, and all participants who use low-power Bluetooth headphones or earplugs can listen to TV audio content. Similarly, when emergency flight information is broadcast in multiple languages at the airport, passengers on the plane can connect headphones to the flight information system, specify the preferred language, and listen to the flight information in that language.

3. Enhanced Attribute Protocol

Bluetooth 5.2 introduces Enhanced Attribute Protocol (EATT), which is an upgraded version of General Attribute Protocol (GATT). The main advantage of EATT is that it can support concurrent event operation, allow ATT-related data packets from different applications to be interleaved with logical link control and adaptation protocol (L2CAP) data packets, and allow the size of ATT's maximum transmission unit (MTU) to change during the connection process. If multiple applications on a device use the low-power Bluetooth protocol stack at the same time, they may temporarily block each other, and these improvements of EATT can reduce these situations, thus reducing the point-to-point delay of one or more applications, improving the response performance and providing a better user experience. Compared with the original ATT, the enhanced version of EATT has the advantage of security, because it can only be used for encrypted connections.

In order to support EATT, the revised core specification defines a new L2CAP pattern. This new mode is called L2CAP enhanced credit-based flow control mode. As the name implies, this mode provides flow control, thus allowing applications to regard the protocol as reliable.

4. Low power consumption power control function

The third important function added by Bluetooth 5.2 is LE PowerControl. This function enables the device to dynamically optimize the transmission power used in communication to prolong the service life of the battery. The low-power Bluetooth receiver can now monitor the signal strength on the transmitting device and request to change the transmitting power, usually to balance the signal quality and power. This is an important additional function, because the extremely strong signal may saturate the receiving equipment, leading to communication failure; On the other hand, when the signal strength is too low, the bit error rate of the receiving equipment will increase, which will affect the transmission and eventually lead to transmission failure.

LE power control function allows Bluetooth controller to monitor the change of path loss by using the concept of "area" and report it to Bluetooth host. Finally, this function can also improve the memory of other wireless devices using the 2.4GHz frequency range in the environment.

Specific application scenarios of Bluetooth 5.2

1. Private audio sharing: For example, if you have favorite music that you want to share with people around you, you don't need to share the link through Yi Yun, but play the music directly through your mobile phone, so that people around you can connect to your sharing channel.

2. Audio reception of public address equipment: For example, in the gym, different fitness programs will be played on different screens, and there must be interference between them. At this time, different audio will be divided into different groups, and the corresponding audio can be received by accessing the corresponding groups to reduce noise interference. At that time, I will send my aunt A Le, who is dancing in the square dance, an audio Bluetooth headset. Think about it and you will feel that the world is much quieter.

3. Auxiliary reception: The flight train information in the waiting room of the terminal is played in speaker mode, which is difficult for some hearing impaired people or when the environment is noisy. If the flight train information is broadcast through music audio equipment, passengers can receive it through Bluetooth headset or corresponding mobile APP, which can greatly save time and energy.

4. Multilingual real-time translation: In the complex environment of human language, Bluetooth devices are connected to the corresponding language translation channels to receive translation information.

ST 17H66 Bluetooth BLE5.2 chip is the latest 16-pin Bluetooth BLE chip from Lentz Technology. With 512kb Flash+(96kb rom)+64kb SRAM, the Bluetooth protocol stack is solidified, which no longer takes up flash space. 64KB SRAM, used by partitions, can save more user data during standby, can set a larger buffer and support more complex functions. Ad hoc network application conforming to SIG specification. Including multi-node control and simultaneous operation of two master devices and four slave devices.

ST 17H66 has 10 x GPIO,-103dbm @ ble125kbps. Single-ended antenna output, no matching circuit. Support antenna matrix switching and external LNA signal amplification.

The biggest advantage is the reduction of power consumption. Peak current received by previous generation Bluetooth >:13ma; The power consumption of MCU is 0.5 Ma/MHz; The average current in low power mode is >: 40uA. The peak current received by the new Bluetooth is 8.6mA, and the MCU consumes power.