Infrared remote control is currently the most widely used communication and remote control method. The infrared remote control has the characteristics of small size, low power consumption, strong function and low cost. Therefore, infrared TVs are also used in other small devices such as color TVs, video recorders, audio equipment, air conditioners, toys, doorbells, and remote control car signs. In order to change the current car headlight indicator light (hereinafter referred to as the car number device), the defect that cannot be flexibly changed, the infrared remote control is used therein, so that it can easily realize the purpose of changing the car number at a long distance and non-contact. This changes the old model of the previous manual flop.
First, the infrared remote control system of the car number device
The car number on the car, originally controlled by a simple LED digital tube, is very inconvenient to use. In order to control it away from it, an infrared remote control is used. Generally, the infrared remote control system consists of two parts: transmitting and receiving, and applying an integrated circuit chip of the encoding/decoding circuit to perform control operations. As shown in FIG. 1, the transmitting part includes a keyboard matrix, a code modulation, and an infrared transmitter. The receiving portion includes a photoelectric conversion amplifier, a demodulation, and a decoding circuit. The transmission of the infrared transmission each time the code is a key value, that is, a hexadecimal data. In order to be able to send a set of data at a time (such as the train number, usually three decimal digits), we can use the 89C2051 software encoding / decoding method, first enter a group of car numbers, press the send button, all send At the same time, at the time of reception, all data is decoded at one time by the continuous receiving method.
Second, remote control transmitter and its coding
There are many special chips for the remote control transmitter, but in the remote control of the car number, the 89C2051 chip is used. Use P1 port to form matrix scan feedback, get the key value, use internal timer 1 to generate a 38K software timing interrupt, drive P1.0 to generate a 38K square wave, as the infrared modulation fundamental wave, the data to be sent, In serial mode, the baud rate is 1200, with parity, directly sent to the serial port of TXD, and then TXD and P1.0 are logically combined. After 40106 shaping, use the triode to drive the infrared emission tube directly. issue. The schematic diagram is as follows:
Third, infrared remote control receiver and its display
The receiver part is mainly composed of CX20106 and 89C2051, display driver 4094, 2803, data memory and watchdog 25045. After filtering the 38K carrier with the decoding chip CX20106, a set of waveforms is obtained, that is, the serial port with a baud rate of 1200. The data is directly sent to the RXD receiver of 89C2051. The serial port is input by software, the input buffer is obtained, and a set of data is obtained. After the judgment is correct, it is stored in the non-volatile EEPROM 25045, and the data is directly sent to the 4094 by pulse shift mode. After being driven by 2803, the watchdog timing is used at the same time to ensure that the program can return correctly without causing erroneous reception in case of program out of control. Due to the serial port mode transmission, it has parity check and stop bit check, which can greatly improve the reliability of the data. At the same time, the accumulation and check are added to the data group, which improves the reliability again. In the application, even in the harsh environment such as open air, direct sunlight, and strong illumination, it can guarantee that the data will not be received by mistake and cause display errors. The schematic diagram is as follows:
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