Who can say no to a Bluetooth speaker that can do voice recognition without relying on the network? The reason for doing this project is also due to the indisputable WIFi at home, which has caused tmall elf to accumulate dust for a long time,I just learned that the CI1302 third-generation voice chip launched by Qiying Tailun has a super high recognition rate,Voice wake-up words and replies can be modified by themselves,It even provides an offline voice Bluetooth audio solution,Doesn't this just solve my needs,Let's take a look at this plan together,Learn it, you can also design your own Bluetooth speaker~

1. Circuit analysis

When designing the circuit, you need to understand the core chip first, and the CI1302 chip of Qiying Tailun is selected here, with a maximum CPU frequency of 220MHz and a working voltage range of 3.6V~5.5V. It has 1 IIS, 3 UART interfaces, 1 IIC interface, 6 PWM interfaces and 10 GPIO ports, which can be controlled independently or used with microcontrollers or other chips. This chip supports 300 offline command entries, and it also supports the self-learning function of command words, which can be used to modify wake words and replies at will through the learning function, which is still very convenient.

There happens to be an evaluation board with Bluetooth function on the official website of Qiying Tailun, download the evaluation board information on the official website, and refer to its schematic diagram to design the following circuit:

In the PCB design, it is necessary to pay attention to the placement of C10, C11, C12 and C15 close to the chip, serial port 0 is reserved for program download, serial port 1 is used for Bluetooth communication, and the digital and analog ground are separated and connected with R5 resistor. The power supply is convenient for daily use, Type-C power supply, through the HT7336 step-down chip output 3.6V power supply to the Bluetooth chip, microphone input through two 100nf capacitor filtering.

The bluetooth chip adopts the AB5607E chip of Zhongke Lanxun, the peripheral circuit is simple, and the antenna circuit is directly connected to the voice recognition chip after a separate design, and the 26M crystal oscillator needs to be selected 20PF ±20PPM to avoid not working.

If you want good sound sound, power amplifiers are indispensable. In the design can be combined with their own needs to choose mono or two-channel power amplifier, here is a commonly used cheap D class power amplifier chip 8002A, R10 is the pull-up working resistance, the sound signal enters the chip No. 4 pin through the RC filter, R15 is the feedback resistor connected to the output pin VO1 to form an inverting amplification circuit, the amplification can be changed by adjusting the size of R15 to change the output sound volume, here can be combined with the actual selection of the speaker to adjust the sound amplification. The magnification is: -HPOUT*R13/R15+(-DACL-BL*R14/R15).

The speaker here is a 4Ω3W speaker, high, medium and low three frequencies in one, the sound quality is OK, the point is that this speaker is cheap enough!!

2. Shell design

After designing the PCB, you can directly design the shell file in EasyEDA Professional Edition, the shell design becomes very simple here, you only need to combine the board frame to set the shape and size of his shell, cut holes in the corresponding position, and set up screw posts for support. The designed model is shown in the following figure:

3. 3D printing

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4. References

If you want to know more about offline speech recognition technology, you can directly visit the official website of Qiying Tailun to explore, which has a large number of application solutions and firmware for learning and reference: