Bluetooth adapter control board development and design

With the steady development of the national economy, people's living standards have been greatly improved, and the demand for mobile communication is becoming more and more urgent. It is this urgent demand of people that promotes the rapid development of modern wireless communication technology. Wireless communication technology can meet people's needs for flexible access to information services, not only on smart phones and computers, but also on fixed phones in offices and homes. Although mobile phones with various functions are developing rapidly, fixed phones have their irreplaceable characteristics. The advantage of a fixed phone over a mobile phone is that it will not be unable to talk because of no power or no signal, and has good stability. At the same time, because of its fixed location, it has brought certain credibility to office and marketing. Therefore, it remains irreplaceable. Although the fixed phone is important, its wired connection has brought a lot of inconvenience to people. The fixed phone can only be answered at a fixed location, and the hands will be occupied and cannot do other things. At the same time, compared with the mobile phone, its intelligence, information storage The quantity is also very different. People are in urgent need of such a telephone, which can not only maintain the stable and reliable advantages of fixed telephones, but also have the advantages of convenience and flexibility of mobile phones and computers. The bluetooth adapter for wired phones designed in this paper can meet people's such requirements.

1. Bluetooth adapter system design

The wired telephone Bluetooth adapter system is mainly composed of a polarity conversion circuit, a ringing circuit, a call circuit and a Bluetooth module circuit. The system block diagram is shown in Figure 1.

Through this adapter, mobile phones, PDAs, tablet PCs, computers and other devices with Bluetooth call functions can make and receive calls through fixed telephone lines. You only need to develop corresponding Bluetooth call software programs on these devices, The application software developed on computers and other equipment can also realize functions such as sending and receiving faxes and data files.

1.1 Ringing circuit

The main function of the ringing circuit is to receive the ringing signal on the telephone line, convert it into a signal recognizable by the Bluetooth chip and provide it to the Bluetooth chip.

Since the telephone line is an AC voltage signal, it becomes a DC signal after being rectified and filtered by the polarity conversion circuit. The signal on the line is connected to the ringing circuit after being rectified, filtered and stabilized. When the ringing signal of AC 90±15V and 25Hz appears on the telephone line, the output terminal OUTPUT of the ringing circuit KA2411 will output a center frequency of 0 The frequency value of the signal is determined by the values of R and c. The frequency selection circuit LM576 selects the frequency of its input signal. When the frequency of the input signal is the same as the center frequency set by C and C. At the same time, the LM576 outputs a low-level signal to the PIO2 terminal of the Bluetooth chip, and the Bluetooth chip detects this signal to know whether there is a ringing signal input.

1.2 Call circuit

The main function of the call circuit is to receive the prompt tone and voice signal on the telephone line, and send out the dual-tone multi-frequency or pulse dialing signal and voice signal through the circuit.

When it is necessary to answer the phone or dial out (equivalent to the off-hook state of a fixed phone), the Bluetooth chip controls the relay K to pull in, and the rectified and filtered telephone line signal is connected to the call circuit through a stabilized voltage, and then sent through the call circuit TEA1061 Connect with the receiving circuit and the Bluetooth chip. Since the voltage of the TEA1061 is different from that of the Bluetooth chip, the output of the SPK terminal of the Bluetooth chip must be amplified by a transformer before being input to the MIC terminal of the TEA1061, and the output of the TEA1061 is sent to the MIC terminal of the Bluetooth chip. The signal must also be attenuated by voltage division through R.

PCD3312C is a dual-tone multi-frequency signal generator. It is controlled by the izC bus of the Bluetooth chip PIO5 and PIO6 to generate a dual-tone multi-frequency dialing signal and input it to TEA1061. PIO3 and PIO4 output by the Bluetooth chip are used to control mute and TEA1061 low power consumption respectively. Power supply.

1.3 Bluetooth module circuit

The main function of the Bluetooth module circuit is to complete various digital voice processing, realize the Bluetooth protocol and control various parts of the system. It can be used to store the information of the Bluetooth device connected to it, so as to realize automatic search and connection. computer, etc. for wireless communication. It is the core of the wired phone Bluetooth adapter. The BlueCore5 embedded platform has a high-performance on-chip DSP, which can support the Bluetooth platform of the third-party audio enhancement software and can provide excellent sound quality. The main chip adopts CSRBlueCore5MM design. It integrates the radio frequency and baseband control of the Bluetooth system, the 16-bit MCU of the RISC structure and the Kal-imba DSP with a performance of up to 64MIPS in the form of a single chip. It only needs to be equipped with a few peripheral components to realize its powerful functions. AVRCP transmission establishes a connection with any Bluetooth device of the remote control protocol to realize wireless communication with the audio gateway. The chip is embedded with a powerful KalimbaDSP data processor, which can complete various digital voice processing.

For the convenience of use, this adapter is powered by the telephone line, but the power that the telephone line can provide is limited, generally only a few hundred milliwatts at the highest, and the telephone line can provide power at different times of standby, ringing and talking. The power supply power is also different, and it cannot provide enough power for the adapter. Therefore, this design uses a commonly used 3.7V lithium battery as the power supply for the adapter. Since the charging current of the lithium battery is very small, it can be powered by the telephone line for the battery. Charging, rectify and filter the input signal of the telephone line, and then use the 781305 to stabilize the voltage for the Bluetooth chip to charge the battery. SST39WF800A-90 is 8M FLASH program memory, AT24C128 is 128k EPROM, which can be used to store the information of Bluetooth devices connected to it, so as to realize automatic search and connection.

The function of PIO7 is to control the relay K to realize the switching between the ringing circuit and the talking circuit of the input signal of the telephone line.

2. Bluetooth adapter software design

In the bluetooth chip CSRBlueCore5MM, the MCU part implements the bluetooth protocol stack and application software, and the DSP is used to implement audio and voice processing and the encoding and decoding of streaming music files. The software development of BC5-MM is carried out on the Roadtunes-SDK provided by CSR. The Roadtunes-SDK provides a completed protocol stack and profile library, as well as software solutions for Bluetooth applications, suitable for single-chip embedded development.

The application software mainly includes initialization, connection establishment, ringing detection, prompt tone detection, dual-tone multi-frequency signal output and voice call and other components.

The adapter is connected with communication devices such as mobile phones through password matching, which can prevent illegal devices from accessing people. If the device has been matched before, it can automatically connect to reduce matching operations.

The ringing signal is obtained through the ringing circuit, and the disconnection, off-hook request and dialing request are sent to the Bluetooth adapter through communication devices such as mobile phones.

Current smart phones generally have Bluetooth connection and data communication functions, and the call application software on the mobile phone terminal is similar to the mobile phone WIFI phone software.

epilogue

Using the wired phone Bluetooth adapter designed in this paper, it can be connected with devices with Bluetooth communication functions such as mobile phones, PDAs, tablet computers and computers, and it is very convenient to develop Bluetooth communication software programs on these devices. The adapter also acts as a small telephone switch among the multiple devices connected to it, and any device can make and receive calls over the phone line. The use of this adapter not only overcomes the disadvantages of the small mobile range of the handset of the landline telephone, the weak signal of the mobile phone in some places, the poor quality of the WIFI telephone call and the long delay, but also maintains the advantages of the fixed telephone signal and the powerful function of the mobile phone. It will bring great convenience for places such as small offices and family residences to make and receive calls.

The above is the design and development example of the fixed-line Bluetooth adapter introduced by Shenzhen Zuchuang Microelectronics Co., Ltd. for you. If you have Bluetooth adapter control board development needs, you can trust us. We represent a variety of single-chip microcomputers, voice chips, dual-mode Bluetooth ICs, and wifi chips. Brands include Songhan MCU, Yingguang MCU, Jerry Bluetooth, Ankai Bluetooth, Allwinner, and Realtek. Our technical services include: PCB design, microcontroller development, Bluetooth solutions, software and hardware custom development, APP development, small program development, WeChat official account development, etc. It can also undertake the design of intelligent electronic products, the development of living appliances, the research and development of beauty equipment, the application of Internet of things platform, the smart home control system, the development of TWS earphones, Bluetooth earphone speakers, the development of children's educational toys, the design of electronic education products, etc.