Assembly language design of digital voltage meter digital tube based on 51 single chip microcomputer and ADC0808

Preface

Hello everyone, the last blog post was about a digital voltmeter based on the 51 single-chip microcomputer and ADC0808, but it used C language. This chapter will talk about using assembly language to achieve voltage measurement, also using digital tube display.

hardware design

The MCU used in this design is also a 51 single-chip microcomputer, the ADC also uses TI's ADC0808, and the display part uses a 4-bit digital tube. The final test voltage range is 0~5V. This time the accuracy is improved to about 0.01V. The simulation diagram is as follows:

The lower right is the simulated input voltage

Some of the assembly code is as follows: (Detailed comments in the code for easy reading)

    LED_0 EQU 30H ; Percentile

        LED_1 EQU 31H ; tenth place

        LED_2 EQU 32H ; Units digit

        LED_3 EQU 33H ; Tens place

        ADC EQU 35H

        CLOCK BIT P1.4 ; define 0808 clock bit

        ST BIT P1.5

        EOC BIT P1.6

        OE BIT P1.7

ORG 0000H

LJMP START

ORG 000BH

LJMP INT_T0

        ORG 30H

START: MOV LED_0,#00H

MOV LED_1,#00H

MOV LED_2,#00H

MOV DPTR,#TABLE ; Assign table value to DPTR

MOV TMOD,#02H ;Timer selection mode 2

MOV TH0,#0F5H ; To prevent the digital tube from flickering, the setting can be set to a number less than or equal to 245

MOV TL0,#00H

MOV IE,#82H ; Open T0 interrupt

SETB TR0 ;T0 starts counting

WAIT: CLR ST

SETB ST ; Rising edge clears SAR (SAR is used to store transient digital quantities during A/D conversion)

CLR ST ; Falling edge starts ADC operation

JNB EOC,$ ; Wait for conversion result

SETB OE ;ADC output

MOV ADC,P2 ; read AD conversion results

CLR OE

MOV A,ADC

MOV R7,A ; R7 stores the result of AD conversion

MOV LED_3,#00H ; Clear the tens digit

MOV LED_2,#00H ; Clear the ones place

MOV A,#00H

LOOP1: ADD A,#20H ; one bit of binary code corresponds to 100mV

DA A ; Convert the result into BCD code

JNC LOOP2 ; Cy is 0 to jump, Cy is 1 to continue execution

MOV R4,A ; R4 stores percentiles and tenths

INC LED_2 ; add 1 to the unit digit

MOV A,LED_2

CJNE A,#0AH,LOOP4 ; Jump if the unit digit is not 10, continue execution if it is 10

MOV LED_2,#00H ; position 0

INC LED_3 ; Tens digit plus 1

LOOP4: MOV A,R4

LOOP2: DJNZ R7, LOOP1 ; R7 minus 1, if not 0, jump, if 0, continue execution

ACALL BTOD1

LCALL DISP ;Call display subroutine

LJMP WAIT

ORG 0200H

BTOD1: MOV R6,A ; R6 stores the value of A after R7 is 0

File address:

Link: https://pan.baidu.com/s/146k5nKjulFsZeTJUKEvQDQ

Extraction code: cukz