[video game training] real topic of 2013 video game of infrared optical communication device

Infrared optical communication device

One 、 Subject requirements

A hybrid signal transmission communication device based on infrared light is designed and manufactured .

1、 The basic requirements
（1） Infrared light communication device uses infrared light emitting tube and infrared light receiving tube as transceiver , Used for directional transmission of voice signals , The transmission distance is 2m.
（2） The transmitted voice signal can be microphone or Φ3.5mm Audio jack line input , It can also be input by low-frequency signal source ; The frequency range is 300~3400Hz.
（3） The received sound shall be free from obvious distortion . When the input voice signal at the transmitter is changed to 800Hz Monosyllabic signal , stay 8Ω On resistive load , The effective value of the output voltage of the receiving device shall not be less than 0.4V. Do not change the circuit state , Reduce the amplitude of the input signal at the transmitter to 0V, Use low frequency millivoltmeter （ The low frequency millivoltmeter displays the effective value , The low end of the frequency response range shall not be greater than 10Hz、 High end not less than 1MHz） Measure the noise voltage at the output of the receiving device at this time , The reading is not greater than 0.1V. If the receiving device is equipped with silencing function , The function must be turned off for the above test .
notes ： If there is no low-frequency millivoltmeter , You can also use an oscilloscope to measure the noise voltage at the output . （4） When the receiving device cannot receive the signal transmitted by the transmitting end , Use a light-emitting tube to indicate .

2、 Play part
（1） Add a digital channel , Real time transmission of transmitter ambient temperature , And can display... At the receiving end . The delay of digital signal transmission shall not exceed 10s. The temperature measurement error shall not exceed 2℃. Voice signals and digital signals can be transmitted at the same time .
（2） Design and make an infrared optical communication relay forwarding node , To change the direction of communication 90°, Extend the communication distance 2 m, Pictured 2
Shown . The quality requirements of voice communication are the same as the basic requirements （3）. Relay forwarding node adopts 5V DC single power supply , The circuit is shown in Figure 3. The series connected milliammeter is used to measure the DC current of its power supply .
（3） In meeting the play part （2） Under the required conditions , Try to reduce the power supply current of relay and forwarding node .
（4） other .

3、 explain
（1） The communication channel of the device must adopt infrared optical channel , Do not use other communication devices . The transmitter and the forwarding node must use discrete infrared light emitting tubes as transmitting devices , The light emitting tube shall be exposed during installation , For inspection . Infrared light emitting chips or modules with internal ready-made communication protocols shall not be used .
（2） Orders received by relay forwarding nodes are excluded 5V Outside the power supply , Do not use other power supply devices （ Such as batteries 、 Super capacitor, etc ）.
（3） When testing , Self provided MP3 Or recorder and audio cable .

Two 、 The project design

The whole device is divided into sending part and receiving part . The sending part selects STM32F103C8T6 SCM minimum system board and temperature sensor ds18b20 Reading temperature , be based on UART agreement , utilize AD9833 and CD4051 Analog switches produce corresponding 2ASK Modulation signal . The temperature signal and sound signal are sent out through the infrared transmitting tube , And received by the receiving device , After signal separation and processing, audio signal and digital signal are output respectively , The audio signal is sent through the horn ,STM32F103RCT6 The single chip microcomputer receives the processed signal and decodes , Display the temperature on the display .

Simulation part

The digital part

The basic idea is as follows ：

• Transmitter

System diagram	Code flow chart	A physical picture

Temperature information collection can choose DS18B20、DHT11 And other modules directly obtain the temperature data through the serial port , Optional Pt100 The temperature measuring circuit of the thermoelectric sensor is set up ADC Sampling to obtain temperature information . For the convenience of this exercise DS18B20 sensor .

DS18B20 Sensor use reference 》》【 Common sensors 】DS18B20 Detailed explanation of the principle of temperature sensor and routine code

There are several schemes for signal modulation , Include ASK、FSK etc. , For detailed introduction, please refer to 《 Modulation mode of wireless signal OOK、ASK、FSK、GFSK》 One article .
ASK Is the abbreviation of amplitude shift keying modulation , For example, binary , Put binary symbols 0 and 1 They are expressed by different amplitudes （2ASK）.
FSK, A digital modulation technique for data transmission by changing the carrier frequency according to a digital modulation signal , For example BFSK in , Binary system 1 And binary 0 During the transmission of carrier signals of different frequencies .

Send data directly through serial port communication , Easy to debug . In order to realize the transmission of digital signals , First convert the digital signal into analog quantity , because ASK Relatively easier to handle , So choose 2ASK Modulation mode . Through a signal source and a single 8 Channel digital control analog electronic switch CD4051 The combination of can realize this function , The switch is controlled by the serial port signal .

Using parameter ：
DDS output frequency ：38.4kHz ;
DDS Output waveform ： Sine wave ;
Serial port baud rate ：1200;

CD4051 The use of reference 》》 single 8 Channel digital control analog electronic switch CD4051

• The receiver

System diagram	Code flow chart	A physical picture

3、 ... and 、 Actual test

Basically realize the transmission of analog part and digital part , The lost information of the digital part was not repaired after the transfer