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Using the infrared remote control system to achieve single-chip

In Electronic Infomation Category: U | on September 22,2011

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Introduction

With the continuous development of science and MMBZ5226BLT1 datasheet and technology, infrared remote control because of its small size, low power consumption, strong function, and MMBZ5226BLT1 price and low cost is to penetrate all areas, in home appliances, security, industrial control and MMBZ5226BLT1 suppliers and is widely used in daily life, especially in home appliances, security and application in daily life is even more extensive. In this paper, the realization of software decoding chip infrared remote control program, all programs have been effective SCM system debugging. For the hardware circuit, infrared remote control transmitter by the completion of the receiving part of the system only need to add a single-chip infrared receiver tubes can be completed.

1 infrared remote control system

infrared remote control system refers to the use of infrared light to pass control signals to achieve the remote control to control the objects purpose; specific terms, the transmitter emits infrared command signal from the receiver signal and signal processing, and finally achieve the objects of the various functions of the remote control. Infrared remote control system in general by the transmitter and the receiver of two parts: the transmitter includes command buttons, command signal generation circuit, modulation circuit, drive circuit and the infrared emitter; the receiver by the infrared receiving device (such as infrared receiver), pre- demodulation amplifier circuit, the command signal detection circuit, memory and driver circuit, perform circuit. Infrared remote control system in accordance with produce and differentiate instruction methods and characteristics of classification, commonly used frequency division system and the infrared remote control code-division system - - frequency division system is the infrared remote control signal generation circuit to different frequencies of electrical signals representing different control instructions : code-division system is the infrared remote control signal generating circuit with different pulse codes represent different commands.

2 infrared remote control signal code

to a Taiwan company produced PTC PT2222-1 encoding chip for the DVD remote, for example. Infrared remote control sends infrared signals, infrared receiver circuit receiving the infrared signal can be triggered by high-performance digital oscilloscope latch get. Infrared waveform shown in Figure 1:

Figure 1 IR waveforms

in peacetime did not receive the infrared signal, the receivers output level is 1; When a key is pressed. The beginning of a wave of low 9ms 0, then 4.5ms high level 1, followed by 32 bits (4 bytes) of data, which the first and second address byte is the remote control code (has been designed for a remote control, the address code is fixed), the third byte is the remote control key codes. The fourth byte is the remote control key code anti-code. Its role is to check after decoding.

NEC remote control agreement, when the infrared remote control to send the key code data to 0. Waveform shown in Figure 2 should jump on the waveform.

wave total width of 1.15ms. High part of the length of about 550us, low length of about 600US, the waveform shown in Figure 2.

2 key code to 0 when the waveform diagram

and when the infrared remote control key code data transmitted data is 1, the waveform is a total width of 2.25ms on the jumping wave. High level of length of about 1.6ms. Low length of about 650us, the waveform shown in figure 3.

3 to 1 when the key code waveforms

Obviously, 0, 1 wave length and wave length is different. If the start time from the rising edge of the waveform, when the delay to 550us later. Data "0" level is low, the data "1" level is still high until 1 600us only after the low. This leaves us with about 600US a "window" of time. In other words, as long as the monitor after rising to 11 500us 550us sample time, you can use the software method to determine the remote control key code of 1 and 0.

3 key decoding subroutine

above routine, in order to ensure proper decoding of data, data reception is completed in a rigorous data validation, not only to verify the address of the remote control information, but also for remote operation key code data only when the received byte of data adding the third and fourth bytes to 0xFF when that receives the data correctly, which ensures control reliability. Also in the program is actually a recurring time_ONO an interrupt regular program, its role is to prevent the line once the El level error when the program enters an infinite loop, which is run on the assurance of reliability is very important.

4 applications

in the microcomputer application system, as long as the main program call this routine repeatedly, and then receive the keys to a corresponding control action on it. A typical call procedure is as follows, the programs function is to receive a key is when to open one LED, received two keys to open a second LED, received 3 keys at the same time close the two LED.

main program is as follows:

hardware circuit is as follows:

Figure 4 Hardware structure

5 Conclusion

This infrared receiver circuit is relatively simple, stable, with small price decoding infrared remote control can be achieved.

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