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1、Based on AT89C52 LED overviewLED (Light Emitting Diode), light-emitting diode, is a solid state semiconductor devices, which can be directly converted into electricity to light. LED is the heart of a semiconductor chip, the chip is attached to one end of a stent, is the negative side, the other end
2、of the power of the cathode, the entire chip package to be epoxy resin. Semiconductor chip is composed of two parts, part of the P-type semiconductor, it inside the hole-dominated, the other side is the N-type semiconductor, here is mainly electronic. But linking the two semiconductors, among them t
3、he formation of a PN junction. When the current through the wires role in this chip, will be pushing e-P, P zone in the hole with electronic composite, and then to be issued in the form of photon energy, and this is the principle of LED luminescence. The wavelength of light that is the color of ligh
4、t, is formed by the PN junction of the decisions of the material. LED history 50 years ago, people have to understand semiconductor materials can produce light of the basic knowledge, the first commercial diodes in 1960. English is the LED light emitting diode (LED) acronym, and its basic structure
5、is an electroluminescent semiconductor materials, placed in a wire rack, then sealed with epoxy resin around, that is, solid package, Therefore, the protection of the internal batteries can play the role of line, so the seismic performance LED good. LED is the core of the P-type semiconductor and co
6、mponents of the N-type semiconductor chips, the P-type semiconductor and N-type semiconductor between a transition layer, called the PN junction. In some semiconductor materials in the PN junction, the injection of a small number of carrier-carrier and the majority of the extra time will be in the f
7、orm of light energy to release, thus the power to direct conversion of solar energy. PN junction on reverse voltage, a few hard-carrier injection, it is not luminous. This use of injection electroluminescent diodes is produced by the principle of light-emitting diodes, commonly known as LED. When it
8、 in a positive state of the work (that is, at both ends with forward voltage), the current flows from the LED anode, cathode, semiconductor crystals on the issue from the ultraviolet to infrared light of different colors, light and the strength of the currents. Instruments used for the first LED lig
9、ht source instructions, but all kinds of light colored LED lights in traffic and large screen has been widely applied, have a very good economic and social benefits. The 12-inch red traffic lights as an example, is used in the United States have long life, low-efficiency 140 watt incandescent lamp a
10、s a light source, it produced 2,000 lumens of white light. The red filter, the loss-90 percent, only 200 lumens of red light. In the light of the new design, Lumileds companies have 18 red LED light source, including the loss of circuit, a total power consumption of 14 watts to generate the same opt
11、ical effect. Automotive LED lights is also the source of important areas. For general lighting, people need more white light sources. The 1998 white LED successful development. This is the GaN LED chip and Yttrium Aluminum Garnet (YAG) package together cause. GaN chip of the Blu-ray ( p = 465nm, Wd
12、= 30nm), made of high-temperature sintering of the Ce3 + YAG phosphors excited by this Blu-ray after irradiating a yellow, the peak 550 nm. Blue-chip installed in the LED-based Wanxing reflection in the cavity, covered with a resin mixed with YAG thin layer, about 200-500 nm. LED-based tablets issue
13、d by the Blu-ray absorption part of the phosphor, the phosphor another part of the Blu-ray and a yellow light mixed, can be a white. Now, the InGaN / YAG white LED, YAG phosphor by changing the chemical composition of the phosphor layer and adjust the thickness of the 3500-10000 K color temperature
14、can be colored white. This blue LED through the method by white, constructed simple, low-cost, high technology is mature, so use the most. In the 1960s, the use of science and technology workers semiconductor PN junction of The principle of developing a LED light-emitting diodes. At that time, the d
15、evelopment of LED, the materials used are GaASP, its luminous color is red. After nearly 30 years of development, and now we are very familiar with the LED, has been sent to red, orange, yellow, green, blue, and other shade. However lighting necessary for white LED light only in recent years to deve
16、lop, readers here to tell us about lighting with white LED.The LED display screen and video display into the text by LED matrix blocks. Graphic display can be displayed with computer, English, Chinese text and graphics, Video screen using microcomputer control, graphic, image, with real-time, synchr
17、onization, clear information dissemination way play all kinds of information, but also shows 2d, 3d animation, videos, TV, VCD programs and live. The LED display screen display bright colors, stereo sense is strong, such as oil, such as films, widely used in finance, taxation, industry and commerce,
18、 telecommunications, sports, advertising, corporations, transportation, education system, station, port, airport, hospital, shopping malls, hotels, Banks, securities market, market, and construction management of industrial enterprises, Christies and other public places.The LED display can display t
19、he change of digital image; text, graphics, Not only can be used for indoor environment can also be used in outdoor environment, projectors, LCD TV wall, and the incomparable advantages.LED by the wide attention and rapid development, and it is the advantages of itself. These advantages in is: high
20、brightness, working voltage, low consumption, miniaturization, impact resistance and long service life and stable performance. LED the development prospect, is currently towards a higher brightness, higher resistance to climate, higher and higher light shine density evenness, reliability, the direct
21、ion of development. Full-colorThe classification of the LED display1, the color can be divided into gezerThe single color display: single colors (red or green).Double colors: red and green screen, double colors gray, can show 256 levels 65536 colors.Full-color display: red, green, and blue, gray lev
22、el 256 gezer full-color display screen can show more than 1,600 colors.2, according to the classification of display devicesLED digital display: display device for seven yards, suitable for making the clock display screen, interest rates, digital electronic display screen.Pictures of LED dot matrix
23、LCD display device is composed of many: evenly composed of light emitting diode matrix display module, suitable for broadcast text, images of information.LED video display: display device is composed by many light-emitting diodes, video, animation shows various video files.3, by using occasions clas
24、sificationIndoor display: light point is lesser, general 3mm - 8mm, display area of general several ten square meters to.Outdoor screen area to several hundred square meters general dozens, high brightness, can work under the sun, in the wind, rain, waterproof function.4 points, according to the cla
25、ssification of light in diameterIndoor screens: 3mm, 3.75 mm, 5mm,Outdoor screen: 10mm, 12mm and 16mm , 19mm, 20mm, 21mm, 22mm, 26mmThe basic unit of the light outdoor screen for led light cone tube, the principle is a group of red, green, and blue light emitting diode sealed in a plastic tube in co
26、mmon5. Display horizontally scrolling, static, vertical scroll and flip shows, etc. Single block module control drive 12 (maximum control and block), 16X48 matrix 8X8 matrix (or 32X48 matrix), is a single block of MAX7219 (or PS7219, HD7279, ZLG7289 8279 and other similar LED display driver module)
27、12 times (or 24 times)! Can use cascade means any bitmap big screen composed. Show good effect, low consumption, and the cost of using MAX7219 circuit is lower.The LED display inspection method,See appearance, specifications, screen body flatness, screen the attachment within2 look bad, after the li
28、ght screen is not in scope, the screen (generally now basically no)Color consistency, displays text display is normal, the picture to screen, full-color play white, red, green and blue.Technical advantageExisting common indoor full-color scheme comparison:1 the matrix modules: design, color dot matr
29、ix LCD by indoor artifactsAdvantage: the cost of raw materials, production and processing of the most advantage of simple process, quality is stable.Faults: color consistency, Mosaic phenomenon, serious effect.2. Single lamp schemes for solving the bitmap screen color: for outdoor screen technology,
30、 a scheme of pixels, outdoor multiplexing technique (also called pixel sharing technology, virtual pixels to indoor display technology) transplantation.Advantage: color consistency than bitmap module of good way.Weakness: the effect not beautiful, color mixing, horizontal Angle and have off color. P
31、rocess is relatively complex, anti-static high. Actual pixel resolution do 10,000 more difficult.Features Compatible with MCS-51 Products 8K Bytes of In-System Programmable (ISP) Flash Memory 1000 Write/Erase Cycles Fully Static Operation: 0 Hz to 33 MHz Three-level Program Memory Lock 256 x 8-bit I
32、nternal RAM 32 Programmable I/O Lines Three 16-bit Timer/Counters Eight Interrupt Sources Full Duplex UART Serial Channel Low-power Idle and Power-down Modes Interrupt Recovery from Power-down Mode Watchdog Timer Dual Data Pointer Power-off FlagDescriptionThe AT89C52 is a low-power, high-performance
33、 CMOS 8-bit microcontroller with 8K bytes of in-system programmable Flash memory. The device is manufactured using Atmels high-density nonvolatile memory technology and is compatible with the industry standard 80C51 instruction set and pinout. The on-chip Flash allows the programmemory to be reprogr
34、ammed in-system or by a conventional nonvolatile memory programmer.By combining a versatile 8-bit CPU with in system programmable Flash on a monolithicchip, the Atmel AT89C52 is a powerful icrocontroller which provides a highly-flexible and cost-effective solution to many embedded control applicatio
35、ns.The AT89C52 provides the following tandard features: 8K bytes of Flash, 256 bytes of RAM, 32 I/O lines, Watchdog timer, two data pointers, three 16-bit timer/counters, a six-vector two-level interrupt architecture, a full duplex serial port, on-chip oscillator,and clock circuitry. In addition, th
36、e AT89C52 is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes.The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial port, and interrupt system to continue functioning. The Power-down mode saves the RAM conten
37、ts but freezes the oscillator, disabling all other chip functions until the next interrupt or hardware reset.In the Counter function, the register is incremented in response to a 1-to-0 transition at its corresponding external input pin, T2. In this function, the external input is sampled during S5P
38、2 of every machine cycle. When the samples show a high in one cycle and a low in the next cycle, the count is incremented. The new count value appears in the register during S3P1 of the cycle following the one in which the transition was detected. Since two machine cycles (24 oscillator periods) are
39、 required to recognize a 1-to-0 transition, the maximum count rate is 1/24 of the oscillator frequency. To nsure that a given level is sampled at least once before it changes, the level should be held for at least one full machine cycle.InterruptsThe AT89C52 has a total of six interrupt vectors: two
40、 external interrupts (INT0 and INT1), three timer interrupts (Timers 0, 1, and 2), and the serial port interrupt. These interrupts are all shown in Figure 10. Each of these interrupt sources can be individually enabled or disabled by setting or clearing a bit in Special Function Register IE. IE also
41、 contains a global disable bit, EA, whichdisables all interrupts at once. Note that Table 5 shows that bit position IE.6 is unimplemented. In the AT89C52, bit position IE.5 is also unimplemented.User software should not write 1s to these bit positions, since they may be used in future AT89 products.
42、 Timer 2 interrupt is generated by the logical OR of bits TF2 and EXF2 in register T2CON. Neither of these flags is cleared by hardware when the service routine is vectored to. In fact, the service routine may have to determine whether it was TF2 or EXF2 that generated the interrupt, and that bit wi
43、ll have to be cleared in software. The Timer 0 and Timer 1 flags, TF0 and TF1, are set at S5P2 of the cycle in which the timers overflow. The values are then polled by the circuitry in the next cycle. However, the Timer 2 flag, TF2, is set at S2P2 and is polled in the same cycle in which the timer o
44、verflows.Reference data:1. the ATMEL company AT89S52 technical manuals2.Shenzhen Development Co., Ltd. AT89C52 3.Fudan University Press, single-chip microprocessor theory, application and test ZHANG You-de, etc.基于AT89C52的LED概述LED（Light Emitting Diode），发光二极管，是一种固态的半导体器件，它可以直接把电转化为光。LED的心脏是一个半导体的晶片，晶片
45、的一端附在一个支架上，一端是负极，另一端连接电源的正极，使整个晶片被环氧树脂封装起来。半导体晶片由两部分组成，一部分是P型半导体，在它里面空穴占主导地位，另一端是N型半导体，在这边主要是电子。但这两种半导体连接起来的时候，它们之间就形成一个“P-N结”。当电流通过导线作用于这个晶片的时候，电子就会被推向P区，在P区里电子跟空穴复合，然后就会以光子的形式发出能量，这就是LED发光的原理。而光的波长也就是光的颜色，是由形成P-N结的材料决定的。LED历史50年前人们已经了解半导体材料可产生光线的基本知识，第一个商用二极管产生于1960年。LED是英文light emitting diode（发光二
46、极管）的缩写，它的基本结构是一块电致发光的半导体材料，置于一个有引线的架子上，然后四周用环氧树脂密封，即固体封装，所以能起到保护内部芯线的作用，所以LED的抗震性能好。 发光二极管的核心部分是由P型半导体和N型半导体组成的晶片，在P型半导体和N型半导体之间有一个过渡层，称为P-N结。在某些半导体材料的PN结中，注入的少数载流子与多数载流子复合时会把多余的能量以光的形式释放出来，从而把电能直接转换为光能。PN结施加反向电压时，少数载流子难以注入，故不发光。这种利用注入式电致发光原理制作的二极管叫发光二极管，通称LED。 当它处于正向工作状态时（即两端加上正向电压），电流从LED阳极流向阴极时，半
47、导体晶体就发出从紫外到红外不同颜色的光线，光的强弱与电流有关。 最初LED用作仪器仪表的指示光源，后来各种光色的LED在交通信号灯和大面积显示屏中得到了广泛应用，产生了很好的经济效益和社会效益。以12英寸的红色交通信号灯为例，在美国本来是采用长寿命、低光效的140瓦白炽灯作为光源，它产生2000流明的白光。经红色滤光片后，光损失90%，只剩下200流明的红光。而在新设计的灯中，Lumileds公司采用了18个红色LED光源，包括电路损失在内，共耗电14瓦，即可产生同样的光效。 汽车信号灯也是LED光源应用的重要领域。 对于一般照明而言，人们更需要白色的光源。1998年白光的LED开发成功。这种
48、LED是将GaN芯片和钇铝石榴石（YAG）封装在一起做成。GaN芯片发蓝光（p=465nm，Wd=30nm），高温烧结制成的含Ce3+的YAG荧光粉受此蓝光激发后发出黄色光射，峰值550nm。蓝光LED基片安装在碗形反射腔中，覆盖以混有YAG的树脂薄层，约200-500nm。 LED基片发出的蓝光部分被荧光粉吸收，另一部分蓝光与荧光粉发出的黄光混合，可以得到得白光。现在，对于InGaN/YAG白色LED，通过改变YAG荧光粉的化学组成和调节荧光粉层的厚度，可以获得色温3500-10000K的各色白光。这种通过蓝光LED得到白光的方法，构造简单、成本低廉、技术成熟度高，因此运用最多。 上个世纪6
49、0年代，科技工作者利用半导体PN结发光的原理，研制成了LED发光二极管。当时研制的LED，所用的材料是GaASP，其发光颜色为红色。经过近30年的发展，现在大家十分熟悉的LED，已能发出红、橙、黄、绿、蓝等多种色光。然而照明需用的白色光LED仅在近年才发展起来，这里向读者介绍有关照明用白光。 LED显示屏分为图文显示屏和视频显示屏，均由LED矩阵块组成。图文显示屏可与计算机同步显示汉字、英文文本和图形；视频显示屏采用微型计算机进行控制，图文、图像并茂，以实时、同步、清晰的信息传播方式播放各种信息，还可显示二维、三维动画、录像、电视、VCD节目以及现场实况。LED显示屏显示画面色彩鲜艳，立体感强，静如油画，动如电影，广泛应用于金融、税务、工商、邮电、体育、广告、厂矿企业、交通运输、教育系统、车站、码头、机场、商
