2013 Question F: Infrared optical communication device

The infrared optical communication device in the question requires the use of infrared light-emitting tubes and infrared receiving modules for communication. It also has requirements for signal-to-noise ratio, communication distance, and digital channels. So a relatively simple implementation solution is to use digital infrared transmission protocol. This project uses the IrDA protocol for communication, and the communication rate of IrDA can reach 4M. If you use the speex open source library to compress the audio digital signals collected by the ADC, you can further reduce the IrDA transmission rate. Since the IrDA rate supported by the microcontroller is generally only 115200bps, audio compression is indispensable. At the same time, the IrDA protocol only has high requirements for decoding on the receiving end, and the transmitting end only needs a transistor or a MOS-driven high-speed infrared LED. In addition, the non-return-to-zero coded communication format of IrDA determines that the overall high-level duty cycle of the transmitter is very small. Therefore, even if the operating current of the infrared LED is increased, the average current consumption of the transmitter module is still very small, but the communication distance can be obtained A big improvement, which can well meet the requirements of the topic. For temperature transmission, the LM75 chip is used to insert identification characters into the audio transmission frame, so that the receiving end can distinguish the transmitted temperature information and print it out through the serial port.