How to Use AT89C51 Single Chip Microcomputer to Control the Circuit Design of LED Display Screen

LED display screen is widely used in industrial and mining enterprises, schools, shopping malls, shops, public places, etc. for graphic display, advertising and information release. This paper designs a system composed of four 16 The display screen composed of 16 dot matrix LED module is controlled by single chip microcomputer to smoothly move and display any number of words or graphic symbols. This circuit can be cascaded and expanded to realize any number of 16 Display screen composed of 16 dot matrix LED module.1 circuit design

How to Use AT89C51 Single Chip Microcomputer to Control the Circuit Design of LED Display Screen 1

The control circuit is controlled by AT89C51 single chip microcomputer, and the display screen is composed of 4 16 16 dot matrix LED modules, each 16 The 16 dot matrix LED module consists of 4 8 Composed of 8-dot matrix LED modules, users can expand and add any number of 16 as needed 16 dot matrix LED module. eight The structure of 8-dot matrix LED module is shown in Figure 1, with a total of 8 rows and 8 columns. Each LED is placed at the intersection of row line and column line, with a total of 64 LEDs. When a column is at high level and a behavior is at low level, the corresponding LED is on.

The P3.0 pin of the single chip microcomputer is connected to the serial data input of the serial input and parallel output shift register 74LS164 (U10), eight 74LS164 (U10 U17) are cascaded, and the P3.1 pin is connected to the clock pulse input of eight 74lsl64; Eight 74LS164 are respectively connected to eight latches 74ls373 (U18 u25), and the data output terminals of the eight latches are connected to four 16 Row line of 16 dot matrix LED module, each 16 The line of 16 dot matrix LED module is controlled independently. P1. O is connected to 8 clock pulse inputs of 74LS164 (U2 u9), P1.1 is connected to serial data inputs of U2, U4, U6 and U8, and every two 74lsl64 (U2 and U3, U4 and U5, U6 and U7, U8 and u9) are cascaded; Four 16 parallel data output terminals of U2 u9 are connected 64 array lines of 16 dot matrix LED module. P1.2 is connected to the clear 0 terminal of all 74lsl64, and p1.3 is connected to the latch control terminal of the latch.

2 working principleThis circuit uses the serial communication port to work in mode 0, and uses P1. O and P1.1 to simulate the serial output to realize the smooth moving display of LED display characters. Because the LED module is 16 16 dot matrix, so the character dot matrix is also 16 16 dot matrix, that is, each character is composed of 32 bytes, that is, 16 word data. Each word data determines the lighting of each column of LED. sixteen 16 dot matrix character data is obtained by character dot matrix extraction software.

Firstly, the single chip microcomputer P1.1 serially outputs a binary bit "1", which is sent to four 16 bits through four groups of 74lsl64 The first column of 16 dot matrix LED module is sent to a high level, and then four 16 bits are output serially by P3. O The row data in the first column of the 16 dot matrix LED module, that is, the row data in columns Y1, y17, y33 and y49, is sent to the row line of the LED display screen after being locked by 74ls373. At this time, the corresponding LED in the first column of each LED module is on. The row data of each column is one word data, and there are four word data in four columns. The address difference of the first byte of each word data in the character dot matrix data table is 32. At this time, each LED module displays the first column of each character. Then P1.1 serially outputs one binary bit "0", which is shifted by four groups of 74LS164, and then sends a high level to the second column of four LED modules, and then P3. O serially outputs four 16 bits The row data in the second column of the 16 dot matrix LED module, that is, the row data in columns Y2, Y18, y34 and Y50, is latched by 74ls373 and sent to the row line of the LED display screen. At this time, the LED corresponding to the second column of each LED module is lit, that is, the second column of each character is displayed. In this cycle, turn on the corresponding LEDs in each column of each LED module in turn until the 16th column of each LED module is turned on, that is, the columns of each character are displayed in turn. As long as the alternating display time of each column is appropriate, and using the visual persistence characteristics of human eyes, it seems that 16 columns of LEDs are lit at the same time, that is, the whole character is displayed at the same time. Then scan the display from column 1 to column 16, and cycle for many times to ensure that the displayed characters have sufficient brightness.

How to Use AT89C51 Single Chip Microcomputer to Control the Circuit Design of LED Display Screen 2

In order to achieve the effect of smooth moving display of characters, after the above four characters are statically displayed for a certain time, when scanning the display again, the first column of each LED module starts from the second column data of each character, that is, the first LED module displays the second column, the third column,..., the 16th column of the first character and the first column of the second character, The second LED module displays the second column, the third column,..., the 16th column of the second character and the first column, the second column,... Of the third character. In the third scanning display, the first column of each LED module starts scanning display from the third column data of each character, that is, the first LED module displays the third column, the fourth column,..., the 16th column of the first character and the first column and the second column of the second character, and the second LED module displays the third column, the fourth column,..., the 16th column of the second character and the first column, the second column,... Of the third character. In this way, the smooth moving display of characters is realized.

3 ProgrammingAccording to the above circuit design and working principle, the control program flow chart of this circuit is drawn. Write the control program according to the program flow chart, and generate the object code file after debugging with wave or keil software.4 circuit simulation

The object code file is added to the single chip microcomputer in the simulation diagram of LED display control circuit drawn by Proteus Software, and the simulation runs. The running results are shown in Figure 4.Circuit design of LED display based on AT89C51 single chip microcomputer5 Conclusion

The LED display control circuit uses a single chip microcomputer as the controller and adopts the serial shift output mode to realize the smooth moving display of a line of characters. In practical application, relevant driving circuits should also be added. The circuit can be extended by any number of 16 16 dot matrix LED module composed of LED display screen display control. The practical application shows that the circuit is stable and reliable, and the effect is good.

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