Principle test of LED electronic large screen control system

First, the purpose and requirements of the experiment To understand the basic principles and implementation methods of LED electronic screen display. Master the method of displaying Chinese character codes and extracting Chinese character codes from standard fonts. 2. Experimental equipment Single-chip microcomputer measurement and control experimental system LED electronic large-screen experimental module Keil development environment STC-ISP program download tool 3. Experimental content Understand the principle of 16*16 display circuit. Write an assembly language program, write a display program for a line of Chinese characters (at least three characters), and be able to cycle display from left to right (or from right to left). 4. Experimental steps 1. Master the control method of the display LED electronic large screen; 2. Use MCS-51 assembly language to display correct Chinese characters and dynamic effects on the LED electronic large screen; 3. Download the compiled program to 51 single-chip microcomputer, observe the display results of the LED electronic screen. 5. Experimental principle The high-brightness LED light-emitting tube constitutes the display, which can display Chinese and English characters, graphics and video dynamic graphics through programming control. The display data of the displayed characters can be written by oneself (that is, directly display the drawing), or can be extracted from the standard font library (such as ASC16, HZ16). The latter requires a correct grasp of the encoding method of the font and the calculation of character positioning. The LED electronic large screen used in the experiment is 16*16 display. Rows and columns each use two shift registers as outputs. When the i-th row output by the shift register is 0 and the j-th column is 1, point (i, j) is lit. In order to be able to display a display font, circular scanning is required, that is, only one row is lit each time, and then 16 display values ​​corresponding to the column are output on the column. Pause for a period of time after outputting a line, and output the next line. In order to achieve a better display effect, the total scanning time of the whole screen is not higher than 40ms. The ranks and columns can be interchanged in the above process. The shift register used in the experiment is 74HC595, which is a device with both serial shift and output latch driving functions. The 74HC595 has an 8-bit shift register and a memory, and a three-state output function. The shift register and memory are clocked separately. Data is input to the shift register on the rising edge of SRCK (shift register clock input), and is input to the storage register on the rising edge of RCK (memory clock input). The shift register has a serial shift input (row Dx (P00), column Dy (P03)), and a serial output (QH), and an asynchronous low level reset, and the storage register has a parallel 8-bit , with a three-state bus output, when enabled (P02 and P07 are low), the data of the storage register is output to the bus. When controlling the 74HC595, first put the data into the SI terminal of the serial input, and then generate a pulse on the serial clock SRCK to output a bit, repeat the above steps 16 times, and output all column values. Then give the memory clock RCK a pulse to latch the serial data. Output the enable terminal to a low level and drive it to the LED electronic screen. The output of the row is only shifted once at a time and re-latched. See the given references for additional information. .