Design of ultrasonic voice ranging cane based on SYN6288

In my country, hearing and speech disabilities rank first among the five major disabilities, including visual disabilities, physical disabilities, and mental disabilities, with 20.57 million people, accounting for 1.67% of the total population of China. In developed countries, most blind people are equipped with guide dogs, but in China, the number of guide dogs is seriously insufficient. How to improve the travel conditions of the blind is a very important task.

In order to facilitate the safe travel of the blind, countries around the world have been developing guide systems. Using ultrasound to detect distance is convenient to design, simple to calculate, and its measurement accuracy can meet the requirements of use. At present, domestically produced ultrasonic guide canes with voice functions have similar problems: on the one hand, the voice chip needs to be pre-recorded before use, which is inconvenient to use. On the other hand, the difference in voice quality caused by different recorders can easily lead to mishearing, and uniform voice quality is required. This article uses the STC89C52R microcontroller and combines ultrasonic ranging technology to design a guide cane, and uses the speech synthesis chip SYN6288 to realize direct text-to-speech conversion without pre-recording. The external speaker reminds the blind of the road ahead and realizes the voice guide function.

1 Working Principle

1.1 Principle of Ultrasonic Distance Measurement

As a new and very useful tool, ultrasound has great room for development in all aspects. Its principle is that the ultrasound emitted by the transmitter propagates at a speed of v in the air, and is reflected back when it touches the object to be measured and received by the receiver. The round-trip time is t, and the distance of the object to be measured can be calculated by s=wt/2.

1.2 TTS speech synthesis principle

TTS (Text To Speech) text-to-speech technology is the development trend of human-computer intelligent dialogue. By using this technology, the pronunciation of the voice chip can be controlled by MCU or PC, and the text instant broadcast function can be realized in various occasions.

The TTS conversion process is to first convert the text sequence into a phonetic sequence, and then the system generates a speech waveform based on the phonetic sequence. This process involves linguistic processing and prosody processing. Currently, the best way to achieve this process is to combine rule-based waveform splicing technology with parameter speech synthesis methods.

2 System Design

2.1 Hardware Design

The hardware circuit mainly consists of four parts: data acquisition circuit, data processing circuit, speech synthesis output circuit and system power supply. Its hardware structure is shown in Figure 1.

The data acquisition circuit is mainly composed of a high-performance KS103 ultrasonic ranging module. KS103 has a temperature compensation function, high measurement accuracy, and uses temperature-corrected ranging commands. The maximum accuracy is 1mm at close range; the minimum measurement blind area is 1 cm, and the maximum range can reach 8 m, with basically no blind areas; it uses the ⅡC interface to communicate with the host and automatically responds to the host's ⅡC control instructions; power saving mode: it has an automatic sleep function. If the module does not receive a host command within 5 seconds, it will automatically enter the sleep state and be awakened by the host's ⅡC control command at any time.

The data processing circuit is composed of a single-chip minimum system, and the MCU uses the 51 series single-chip STC89C52RC. The chip adopts a 40-pin dual in-line package (DIP) and consists of a CPU, 8 kB Flash, 512 B RAM, 4 8b I/O ports: P0, P1, P2, P3, a full-duplex serial communication port, etc. This minimum system is responsible for the data processing function of the entire system.

The speech synthesis transmission circuit is mainly composed of the SYN6288 module and the speaker. The SYN6288 is responsible for realizing the conversion of text to speech (TTS), and the speaker is responsible for issuing sound prompts. SYN6288 is a speech synthesis chip using PSOLA splicing synthesis technology launched by Beijing Yuyin Tianxia Technology Co., Ltd. in early 2010. SYN6288 receives the text data to be synthesized through the asynchronous serial port (UART) communication method to realize the conversion of text to speech (or TTS speech). It can directly drive the speaker through the PWM output method or the external power amplifier circuit to drive the speaker for speech output, and can obtain the current state of the chip by reading the level of the BUSY pin. The chip supports text in formats such as GB2312, supports punctuation, Chinese characters, numbers, English letters and special characters, can correctly identify numerical values, numbers, time and date and commonly used measurement symbols, and has strong polyphonic character processing and Chinese surname processing capabilities. The SYN6288 module pin diagram is shown in Figure 2.

The system power supply is a 5 V rechargeable lithium battery, which can be used repeatedly, energy saving and environmental protection. The hardware circuit diagram of the ultrasonic ranging crutch system based on SYN6288 is shown in Figure 3.

2.2 Software Design

The MCU first initializes the relevant parameters and corresponding modules and sensors, including the settings of the MCU serial port, the ultrasonic module and the SYN6288 speech synthesis module. Then the MCU reads the value of the KS103 ultrasonic module through the IIC bus to obtain the information of the obstacle in front. Then the MCU determines whether the SYN6288 is converting the voice by reading the BUSY pin of the SYN6288. If it is, it waits. If not, it converts the obstacle information in front into voice information and sounds it through the speaker for voice prompts. The specific program flow chart is shown in Figure 4.

3 Test Analysis

After experiments, the ultrasonic voice ranging cane designed based on SYN6288 was used to conduct experiments. It can effectively measure within the range of 0 m to 2 m, and the test accuracy is 1 cm. There are certain test errors mainly due to the ultrasonic absorption attenuation and scattering loss of the rough road surface and the attenuation of the emitted ultrasonic wave as the target distance increases.

4 Conclusion

The ultrasonic voice ranging cane designed with the SYN6288 speech synthesis chip is simple to use and easy to operate. It is powered by a +5 V lithium battery, so it has good mobility and a voice prompt function, which is more user-friendly. The high-performance KS103 ultrasonic ranging module is used to correct the transmission speed through temperature compensation, so it has a high measurement accuracy.