用一pIC的A/D判断电压大小,当电压在3.1V和4.3V之间的时候,POTRB 7灯点亮,当电压高于4.3V和低于3.1V的时候,PORTB 3的灯点亮,但是实验中发现A/D采样过的的数值正确,但是不知道怎么判断不出来?
3.1V和4.3V的数字是这样得出来的 .X*5/255=4.3V X=0XDB
X*5/255=3.1V X=0X9Ea,不知道是计算错误还是程序有问题?
;pic:16f877
;2008-11-24
;LED显示
LIST P=16F877A
#INCLUDE<P16F877a.INC> ;包含芯片头文件
__CONFIG _DEBUG_OFF&_CP_ALL&_WRT_HALF&_CPD_ON&_LVP_OFF&_BODEN_OFF&_PWRTE_ON&_WDT_OFF&_HS_OSC
;芯片配置字，看门狗关，上电延时开，掉电检测关，低压编程关，加密，4M晶体HS振荡
;**************************
STATUS EQU 0X03
PORTC EQU 0X07
TRISC EQU 0X87
ADCON0 EQU 0X1F
ADCON1 EQU 0X9F
PIR1 EQU 0X0C
PIE1 EQU 0X8C
INTCON EQU 0X0B
TRISC EQU 0X87
PORTC EQU 0X07
N1 EQU 0X20
;********************
ORG 0X00
NOP
GOTO START
ORG 0X05
START BSF STATUS,5
MOVLW 0X3F
MOVWF TRISC
BCF STATUS,5
MOVLW B'01000001';
MOVWF ADCON0
BSF STATUS,5
BSF STATUS,6
MOVLW B'10000111'
MOVWF OPTION_REG
BSF STATUS,5
BCF STATUS,6
MOVLW B'00001110'
MOVWF ADCON1
BCF STATUS,5
MAIN BTFSS INTCON,2
GOTO MAIN
BCF INTCON,2
BSF ADCON0,2
WAIT BTFSS PIR1,6
GOTO WAIT
MOVF ADRESH,W
SUBLW 0X9E;3.1V-A/D
BTFSC STATUS,0
GOTO FAIL
SUBLW 0XDB;4.3V-A/D
BTFSC STATUS,0
GOTO PASS
GOTO FAIL
;***********************
FAIL BSF STATUS,5
MOVLW 0XBF
MOVWF TRISC
BSF PORTC,6
RETURN
GOTO WAIT
;********************
PASS BSF STATUS,5
MOVLW 0X7F
MOVWF TRISC
BSF PORTC,7
RETURN
GOTO WAIT
;**********************
end
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