Unique LED display word processing system
General LED dot matrix display dynamic display commonly used hardware scan driver, which in some occasions require special display appears not flexible enough. PASSION LED is the use of PC computer and Microcontroller communication to achieve the display of dynamic display and changing the design of remote monitoring methods, while the method can also display the contents of the PC, preview.
LED dot matrix display is a micro electronic technology, computer technology, information processing system in one large display. With its colorful, wide dynamic range, high brightness, long life, stable and reliable and a large display medium and display ideal for outdoor work. Also can be widely applied to the military, railway stations, hotels, sports, news, finance, securities, advertising and transportation and many other industries. Most of the LED dot matrix display system comes with character. The display and dynamic effects (mainly display rolling) rely mainly on hardware implementation of scan driver, although the method is convenient, but the show only in accordance with the design in advance. The fact will always be the special requirements of the dynamic display, such as elevator running up and down arrows in the instructions, some of the bar shows the amplitude of intelligent instruments, advertising display manufacturers mark. At this time, the display system can hardly meet the requirements. In addition, due to the limitations of memory itself, its special characters or patterns are often difficult to show, also shows that content can not be altered. PASSION LED LIGHTING INTERNATIONAL LIMITED is the use of PC, and microprocessor controlled LED display system of communication. This method can display the content (including Chinese characters and special icons) for real-time control, in order to achieve such as flashing, scrolling, typing and other dynamic display. The method can also adjust the speed of dynamic display, and you also can display on PC, preview, real-time display can also be modified. In addition, through the standard RS232/485 converter module also allows remote control of the display system.
System hardware design
System hardware design is the next major slave MCU display control section. The host computer (PC) and single chip display control part of the interface is a standard RS232 communication. For remote control, simply increase the RS232/485 converter module can be, that part of the mature circuit. Specific LED display control circuit shown in Figure 1. The circuit consists of microcomputer 89C52, lattice data memory 6264, column driver circuit ULN2803, line driver circuit TIP122, shift register 4094 and the subsidiary circuit. The circuit is designed electronic screen can display 10 characters, requires 40 8 × 8 LED dot matrix module can be composed of 16 × 160 rectangular lattice. As the only 8k AT89C52 storage, and display the content from the PC machine control, it is not possible to display the content in advance the existence of single chip made of lattice, rather only by the PC, real time data in the required dot matrix display and into the buffer passed to SCM 6264. The circuit shown uses progressive scanning. Work, the buffer removed by the microcomputer from the first row need to display 20 bytes of dot data, lattice data by the column input P1.2 port followed by-bit serial input to the column shift register, the data input sequence and Show content in reverse order. Then set the strobe terminal P1.3 line lattice of 1, which set the D-line shift register is high, STR-enabled (all 4094 of the OE pin is connected +5 V level), so that the column shift register output data in parallel to the row strobe. The delay time before the data to the next line dot matrix display. Note that each row of data can only be gated, that is to continuously achieve progressive scan display of character or characters.
Display and control design
PASSION LED LIGHTING INTERNATIONAL LIMITED PC machine control in the design of single chip multi-display system, with the PC, the main function, including the choice of single chip display subsystem, display options (including static, flashing, scrolling, typing, etc.), rolling direction selection (including up and down scrolling and left and right scrolling), dynamic display speed of adjustment (ie, frequency of flashing text, scrolling speed, typing speed, display), display the contents of input and display preview. Received through the RS232/485 serial microcontroller generally issued PC, the display means by way of line scan timer interrupt, each interrupt display line, timer interrupt time is 1.25ms, so the entire screen refresh rate of 50Hz, so no flicker sense.
Dynamic display of speed adjustment method is usually to change the timer interrupt time, but very slow when the display time, it is easy to make the whole screen refresh rate lower, so that display flicker. Therefore, this design uses a "soft-time" approach, Ji named a variable in the program as a "soft timer", Yi used to set the interval between two dynamic display of Shi Jian. Call count in the timer interrupt, if the number of calls to set the value, change the display. To ensure the normal display, "soft timer" settings must be greater than the entire screen display cycle. As the display of each line shows the 1.25ms, full-screen display period is 20ms, taking into account the margin of the situation, can be soft-timer settings set at greater than 30ms. So the cycle count, dynamic display can be realized. "Soft timer" settings can be changed PC-PC, it can achieve LED dynamic display of speed adjustment, but also to maintain the smooth and non-display of light flashes. 3.1 microcontroller mentioned above, the dynamic display control static, flashing, scrolling, and 4 kinds of display type, in fact MCU line scan timer interrupt handling procedures different ways. The following will explain how to achieve that four kinds of display. Static display only in the timer interrupt handler transferred from the display buffer corresponding line of display data, and then select the line you can achieve the display of the line, so the cycle can display the content. Flashing display Similarly, an interval of difference is a "soft timer" in the regular time, line scan, line side shift register into the whole D 0, can make the whole screen is not displayed to ensure black screen time and display time equal to achieve the character or graphic symbols flashing display. Scrolling required to display the content at regular intervals to the designated direction (from right to left here for example) moving one, so the display can display more content. To do this, before the next mobile display changes to show the contents of the buffer zone, thus completing the shift operation of the corresponding lattice data. Specific methods of operation are: to set up a display buffer (Figure 2), the area should include two parts: one to save the current displayed on LED display 10 character dot-matrix data; another part of the data for the lattice pre- loading area, to save the LED display is about to enter a Chinese character dot-matrix data. Scroll pointer always points to the far right of the screen origin. When the pointer moves to the need for scrolling dot matrix display data storage area 1 of the Chinese characters of the first address, the display buffer LED display area is blank, while pre-loading zone has been saved the first one to be displayed in the dot matrix character data. When you need to scroll, we can scan in the next cycle of each line scan interrupt handler, it will display the corresponding line of dot matrix data buffer left one, and change the display contents of the buffer. (Note that, to ensure that the operation can be completed within the time 1.25ms interrupt. Here 89C52 uses 22MHz crystal, experimental results show that the operation can be achieved). Thus, a scan cycle, the character will be shifted to the left one, and display the contents of the buffer zone also changes. As the pre-loading zone preserved a character dot-matrix data, that is 16 × 16 dot matrix, so the contents of the current display buffer can only move 16. A rolling moment comes, roll the cursor moves to the next dot-matrix data store the first address of a character, and in the pre-loading area into the character of the lattice data. Then repeat the above operation can be achieved scroll.
Showing results should facilitate typing text on the screen one by one from left to right order of appearance, the same effect as typing. Design can use the following method: First the LED display the corresponding display buffer all clear, so that LED display blank, then each interval to make a "soft-timer" to set the dynamic display time, display buffer then added to the character points array data and scans showed that this type shows the effects can be achieved.
Implementation of communication
In the Windows environment, to achieve the communication PC and microcontroller can use Windows API function or use of communications VC + + (or other language) of the standard communication function _inp, _outp to achieve. But the above two methods is relatively more complicated, but using ActiveX controls are very easy to achieve MSComm32. The control is simplified with the way the event the operation of serial port programming, serial communication can be set to send and receive data, but also on the serial communication port status and message format and protocol set. The initialization procedure is as follows: In general, PC systems with multiple microcontroller 89C51 for master-slave communication, to distinguish between Ge MCU system can make use of serial Gongzuo 89C51 mode 3, or 11-bit asynchronous receive / transmit mode, the effective way of data 9, the first of nine for the address / data information of the flag, whose role is to send from machine to judge whether the data address, in order to achieve multi-machine operation. But now, thanks to the PC MSCOMM control to achieve communication between the machine and MCU, which is a standard 10-bit serial communication, that is, the standard 8-bit data bit and the start of the data bits, 1 stop bit different . Therefore, the two formats are incompatible, so difficult to use the program. Therefore could be considered a single chip serial port set to work, to read 10-bit asynchronous receiver / transmitter means to resolve their communication process is as follows: First, mark the beginning made communication, then send the need microcontroller operating system address, and send work orders displayed words, the order includes two bytes, the previous byte is used to set display and rolling direction, after a byte is used to set the display speed. Then is sent down the dot matrix display data, the final validation of the data. The communication protocol is very simple, to better address these issues in order to achieve single chip and multi-PC, the master-slave communication between and control of the display. Note that, when the display needs to change, in order to avoid disruption in the Serial receive data, the display is garbled, should enable the display temporarily shows (in the "black" state), until the data receiving full, serial end of interrupt handling and then display. Critical extraction of Chinese characters, the font data from this paper under the font file UCDOS HZK16. For special characters or dot matrix data extraction, simple way to do first a BMP file, then use some modulo software (such as font extract v2.1) to get. In order to show easy, dot matrix format of the data should be n × (16 × 8), short of the required data should be added to 0.
Simulations show that dynamic effects
LED display to facilitate adjustment effects, you can control the PC-interface design of analog LED display shows the actual display it with exactly the same. Users can set the display mode, and adjust the display speed, and then at the interface of the display to preview, and also can be modified at any time and set parameters, and thus very conveniently and easily. This could describe the first virtual interface, LED display, as the actual display is 160 × 16 dot matrix, and thus should be set at the interface the same area. Dynamic display methods and some basic similar over here to scroll example for a description. For those rolling text, can Jiang set to bitmap format, temporarily stored in memory, Zhong, and then Utilize VC Tigong De Kaobei function BitBlt the bitmap will be copied to the display bitmap Wei Zhi. For special characters or graphics, you can directly use the BitBlt function call to the display position. Then in the class CLEDDlg the OnTimer function call the function, in order to achieve the text of the scroll. Alternatively, you can set different response time intervals to change the text scrolling speed.
Widely used Chinese character display and auto-stop device, advertising screens. This paper presents a practical character display production, taking into account the ease of purchase of circuit elements, do not use 8 * 8 dot matrix LED module, but direct use of 256 high measure of light-emitting tube, formed a 16-line 16 out of the light lattice. at the same time to reduce the production of the difficulty, with only a word in turn shows that the actual use to expand according to the principle of self-display the number of words.
shows the principle characters: We UCDOS Chinese Times New Roman font, for example, each word line 16 by 16 dot matrix display component. The national standard Chinese character library of every word by 256 dots to represent. We can understand each point as a pixel, and the shape of each word understood as an image. In fact the Chinese character display screen not only Chinese characters, also can display 256 pixels in any graphics within. AT89C51 8-bit MCU control, because the bus for the 8-bit microcontroller, a word need to split into two parts. After opening the software to input.chinese characters, point of "seizure" of data in hexadecimal character code can be automatically generated, we need to copy the vertical data into our program can be.
We rank the bus connected to the microcontroller i0 mouth, then the above analysis to the scan code into the bus, you can get the Chinese characters displayed. In this example, use as a total of 16 rows, 16 columns, if all of its access 89c51. SCM, a total of 32 io port to use, so that the depletion of resources caused by the io, the system has no room for expansion. Practice we use the 4-16 line decoder 74ls154 to complete the column direction of the show. The line direction of 16 lines are connected to the mouth and p2 p0 mouth.