Design of electronic billboard circuit based on AT89S51 chip

0 Introduction

Nowadays, neon lights are still used to decorate various buildings in cities. However, neon lights have the disadvantages of high heat generation, low brightness, dark colors, high prices and high power consumption, and are no longer the main choice for decoration. Dot matrix screens have the advantages of low price, long visibility, high brightness, low energy consumption, small size, and can be combined into a larger area of ​​dot matrix blocks by several small dot matrix screens according to actual conditions. Here we mainly introduce the use of AT89S51 as the control chip, and the use of 4 8×8 dot matrix screens to cascade to achieve a 16×16 dot matrix screen, which can be used for billboard display, etc.

1 System Design

In view of the fact that the designed dot matrix screen is a 16×16 monochrome display, it can be realized by cascading 4 8×8 dot matrix screens. At this time, the rows and columns of the dot matrix screen are 16 pins each, and an expansion port is required. The 74LS164 serial input and parallel output are used to achieve it. The entire system uses AT89S51 as the control chip, P0/P2 port as row control, P3 port as the input of the chip 74LS164, and two 74LS164 chips are cascaded for column control. Different codes are called through the software program to display characters or text.

2 Components Introduction

2.1 Introduction to AT89S51 MCU

AT89S51 has 4 KB of programmable flash memory (FLASHProgrammahle AND Erasable Read Only Memory). The on-chip flash memory allows reprogramming in the system, making it very easy to modify the program during system development, and even if there is a program error, it will not become a waste. Because the 8-bit CPU and flash memory are included in the single-chip integrated circuit, AT89S51 becomes a powerful controller, which provides an efficient and flexible solution for many embedded systems. Based on the above reasons, AT89S51 was selected.

2.2 Introduction to 74LS164 Chip

In a single-chip microcomputer system, if the parallel port I/O resources are insufficient and the serial port has no other functions, then 74LS164 can be used to expand the parallel I/O port and save single-chip microcomputer resources. 74LS164 is a serial input/parallel output shift register with a clear terminal.

3 Hardware Design

The circuit in Figure 1 is a connection diagram of an 8×8 dot matrix display circuit.

(1) Connect the P1 port in the "MCU System" area to the "DR1~DR8" ports in the "Dot Matrix Module" area using an 8-pin row;

(2) Connect the P3 port in the "MCU System" area to the "DC1~DC8" port in the "Dot Matrix Module" area using an 8-pin row. If you want to display a large image, you can put multiple dot matrices together, connect the rows and columns in series, and use 741S164 to control a single row.

4 Part of the source code

Some source code is as follows:

SEND: MOV A, R1; send the table first address

ACALL TAB1 ; Check list

5 Conclusion

This paper studies the use of AT89S51 as the control chip and 8×8 dot matrix screen to realize the scrolling display of advertising words, which is of great significance to environmental protection and energy saving.