Realization of digital tube display based on C51

Preface ： This experiment is based on STC89C52RC Single chip microcomputer , Program and control the static and dynamic display of the nixie tube according to the circuit schematic . because 51 The structure of Series MCU is similar , Readers can draw inferences from this blog , Realize the required functions .

---

Catalog :

• One 、 Digital tube introduction
• Two 、 Circuit schematic analysis
• 3、 ... and 、 Realize the static display of nixie tube
• Four 、 Realize the dynamic display of nixie tube

---

The single chip microcomputer selected in the experiment and its structure are displayed ( In general C51 For example , The others are similar ), The buzzer operated in this experiment is located in the serial number ① Location

One 、 Digital tube introduction

Nixie tube is a kind of semiconductor light-emitting device , Its basic unit is light-emitting diode . The development board used in this experiment contains eight digital tubes , Different numbers can be achieved by lighting different nixie tube sequences / Letter display effect . As shown in the figure below , Lighten up {A,B,C,D,E,F} Segment nixie tube , You can display numbers 0 The effect of

The nixie tube can be divided into Common anode digital tube and Common cathode digital tube
️ Gongyang nixie tube It refers to connecting the anodes of all light-emitting diodes together to form a common anode （COM） My digital tube . In the application of Gongyang nixie tube, the common pole should be used COM Receive +5V, When the cathode of a field is low , The corresponding field lights up , When the cathode of a field is high , The corresponding field is not on
️ Common cathode digital tube It refers to connecting the cathodes of all light-emitting diodes together to form a common cathode (COM） My digital tube . In the application of common cathode nixie tube, the common pole should be used COM Connect to the ground wire GND On , When the anode of a field led is at high level , The corresponding field lights up , When the anode of a field is low , The corresponding field is not on
️ example ： To achieve the digital display in a digital tube 0, If the development board is loaded with common anode nixie tubes , As shown in the figure above , It's in { decimal point 、G} Input high level , Low level input of other pins can be achieved ; If the development board is loaded with a common cathode digital tube , On the contrary . The development board used in this experiment is a common cathode 8 Digital tube , The physical drawing of digital tubes with different digits is shown in the figure below ：

LED There are two ways for nixie tube display ： Static display mode and Dynamic display mode . The characteristic of static display is that the segment selection of each nixie tube must be followed by one 8 Bit data line to keep the font code displayed . The feature of dynamic display is to connect all segments of nixie tubes in parallel , The line selection by bit controls which digital tube . In terms of implementation effect , Static display mode is to display one digit / Letter , The display effect of dynamic display mode is multi digit / Letter . The principle of dynamic display mode is Fast selection of multi digit nixie tubes , Static display of each nixie tube , Using the afterglow of the light-emitting tube and the persistence of human vision .

---

Two 、 Principle and circuit diagram analysis

2.1 Segment selection of nixie tube

This experiment is on board Each of the eight sections has a total cathode Nixie tube , Different numbers can be achieved by lighting the nixie tubes of different specified sequences / Alphabetic display . Here are the... Of the common cathode nixie tube 0-F Segment code data table . As shown in the figure below ：

Explain with examples ： Why display numbers 0 The segment selection sequence of is 0x3f

0 ： 0x3f

0x3f Binary representation as 00111111 , Corresponding to each of the nixie tubes 8 paragraph ,“. G F E D C B A”, Expressed by output level , Decimal point segment and G Segment output low level , The output of common cathode digital tube is 0. Other display sequences are analogized .

2.2 Bit selection of nixie tube

This experiment board contains eight digit digital tubes , The single chip microcomputer needs to output a bit selection signal to select which digital tube to display , If each nixie tube is controlled by a single-chip microcomputer pin , And each eight segment needs to be controlled by eight pins of the single chip microcomputer , You need to occupy the MCU 16 Pins are used to control the whole nixie tube system . therefore , For the bit selection of digital tube system , In order to reduce the occupation of MCU pins , There's another one out there 74HC138 The decoder uses three pins to complete the selection of eight digit nixie tubes .38 The decoder is shown in the figure below ：

The principle of 38 decoder is ： Three bits of binary can represent exactly eight numbers . This experimental board uses P2.2、P2.3、P2.4 Three pins for bit selection of the eight digit nixie tube system . Such as the input "111" Select the eighth digit nixie tube

2.3 Circuit diagram analysis

74HC245 Introduction of chip function

In the circuit diagram above , In the MCU pin and nixie tube system, a piece of 74HC245 chip . This is because the non-public anode of the common cathode nixie tube is connected to IC Chip I/O On , and IC The driving ability of chips is often relatively small .74HC245 The chip can increase the driving ability for the output signal of the single chip microcomputer

Display principle

According to the above circuit diagram, it can be analyzed ： Use single chip microcomputer `P22`、`P23`、`P24` The pin selects the position of the nixie tube system , Use single chip microcomputer `P0` The pin of the port carries out segment selection for the nixie tube corresponding to the selection bit .

---

3、 ... and 、 Realize the static display of nixie tube

This experiment uses SMG1 The digital tube on the far left is used as a static digital tube , Because of MCU IO External pull-up resistance is added outside the port , therefore P22、P23、P24 Pin , The default is high , according to 38 Output characteristics of decoder , here Y7 Pin (LED8) The output is valid . The control code is as follows ：

/**************************************************************************************
 Name of the experiment ： Static nixie tube experiment 
 Experimental phenomena ： After downloading the program “ Nixie tube module ” The leftmost nixie tube displays numbers 0																		  
***************************************************************************************/
#include "reg52.h"

typedef unsigned int u16;	// Redefine the system default data 
typedef unsigned char u8;

#define SMG_A_DP_PORT	P0	// Use the macro to define the code port of the nixie tube segment 

// Common cathode nixie tube display 0-F Segment code data 
u8 gsmg_code[17]={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x07,
				0x7f,0x6f,0x77,0x7c,0x39,0x5e,0x79,0x71};

void main()
{	
	SMG_A_DP_PORT=gsmg_code[0];// Assign the first data of the array to the selection port of the nixie tube 
	while(1)
	{
	   	
	}		
}

Experimental phenomena

Four 、 Realize the dynamic display of nixie tube

The essence of nixie tube dynamic display is multi bit static fast display , Use visual residue to realize dynamic display . It needs segment selection and bit selection to work at the same time . The implementation code is as follows ：

/**************************************************************************************
 Name of the experiment : Dynamic nixie tube experiment 
 Experimental phenomena ： After downloading the program “ Nixie tube module ” Show 01234567																	  
***************************************************************************************/
#include "reg52.h"

typedef unsigned int u16;	// Redefine the default data type of the system 
typedef unsigned char u8;

#define SMG_A_DP_PORT	P0	// Use the macro to define the code port of the nixie tube segment 

// Define nixie tube position selection signal control pin 
sbit LSA=P2^2;
sbit LSB=P2^3;
sbit LSC=P2^4;

// Common cathode nixie tube display 0-F Broken code data 
u8 gsmg_code[17]={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x07,
				0x7f,0x6f,0x77,0x7c,0x39,0x5e,0x79,0x71};

/*******************************************************************************
*  Function name        : delay_10us
*  The functionality 		 :  The time delay function ,ten_us = 1 when , About time delay 10us
*  Input       : ten_us
*******************************************************************************/
void delay_10us(u16 ten_us)
{
	while(ten_us--);	
}

/*******************************************************************************
*  Function name        : smg_display
*  The functionality     :  Dynamic nixie tube display 
*******************************************************************************/
void smg_display(void)
{
	u8 i=0;

	for(i=0;i<8;i++)
	{
	   	switch(i)// Biting 
		{
			case 0: LSC=1;LSB=1;LSA=1;break;
			case 1: LSC=1;LSB=1;LSA=0;break;
			case 2: LSC=1;LSB=0;LSA=1;break;
			case 3: LSC=1;LSB=0;LSA=0;break;
			case 4: LSC=0;LSB=1;LSA=1;break;
			case 5: LSC=0;LSB=1;LSA=0;break;
			case 6: LSC=0;LSB=0;LSA=1;break;
			case 7: LSC=0;LSB=0;LSA=0;break;
		}
		SMG_A_DP_PORT=gsmg_code[i];// Transmit segment selected data 
		delay_10us(100);// Delay for a period of time , Wait for the display to stabilize 
		SMG_A_DP_PORT=0x00;// Silencing 
	}
}

void main()
{	
	while(1)
	{
	   	smg_display();
	}		
}

Experimental results

---

Thank you for watching. , If you have doubts or supplements about the content , Feel free to leave a comment , Common progress ！！！