I am writing an assembly code for measuring the distance using ultrasonic sensor and pic18 the problem is I can't get the result to get displayed on the lcd and I don’t know if the steps to measure the distance are correct .
I tried this code
#include <p18f452.inc>
#define _XTAL_FREQ 8000000
#define LCD_DATA PORTD ; Define the data bus port
#define LCD_RS PORTCbits.RC0 ; Define the RS control port
#define LCD_E PORTCbits.RC1 ; Define the EN control port
#define TRIG PORTBbits.RB0 ;TRIG
#define ECHO PORTBbits.CCP1 ;ECHO
PERH EQU 0x10
PERL EQU 0x11
COUNT1 EQU 0x12
COUNT2 EQU 0x13
result equ 0x14
ORG 00
GOTO MAIN
MAIN:
bcf TRISB,0
BSF TRISC,CCP1 ; configure CCP1 pin for input
CALL delay
call init_LCD ; Initialize LCD
MAIN_LOOP:
;bsf PORTB,0
call s_10us_signal
bcf PORTB,0
wait_ECHO:
btfss PORTC,CCP1
BRA wait_ECHO
CALL capture_signal
CALL distance
call delay
GOTO MAIN_LOOP
s_10us_signal:
;BCF TRISB, 0 ; PB0 as an output
BCF PORTB,0 ; PB0 = 0
MOVLW 0X80 ; Timer1, 16 bit, int CLK, no prescaler 0XC0
MOVWF T1CON
MOVLW 0XFF ; TMR0H = FCH
MOVWF TMR1H
MOVLW 0XEC
MOVWF TMR1L
BCF PIR1, TMR1IF
BSF PORTB, 0
BSF T1CON, TMR1ON
WAIT:
BTFSS PIR1,TMR1IF
BRA WAIT
BCF T1CON, TMR1ON
;bcf PORTB,0
RETURN
capture_signal:
CLRF CCP1CON
CLRF CCP1IF
MOVLW 0x80 ; use Timer1 as the time base of CCP1 capture
MOVWF T1CON
BCF PIE1,CCP1IE ; disable CCP1 capture interrupt
MOVLW 0x81 ; enable Timer1, prescaler set to 1,
MOVWF T1CON ; 16-bit, use internal cycle clock
MOVLW 0x05 ; set CCP1 to capture on every rising edge
MOVWF CCP1CON
BCF PIR1,CCP1IF
Edge1:
BTFSS PIR1,CCP1IF ; wait for the first edge to arrive
BRA Edge1
MOVFF CCPR1H,PERH ; save the first edge
MOVFF CCPR1L,PERL
BCF PIR1,CCP1IF ; clear the CCP1IF flag
Edge2:
BTFSS PIR1,CCP1IF ; wait for the second edge to arrive bra edge2
BRA Edge2
CLRF CCP1CON ; disable CCP1 capture
MOVF PERL,W
SUBWF CCPR1L,W ; subtract first edge from 2nd edge
MOVWF PERL ; and leave the period in PERH:PERL
MOVF PERH,W
SUBWFB CCPR1H,W
addwf PERL,result
;MOVWF PERH
RETURN
distance:
movlw d'34'
mulwf result
movlw result
call LCD_data
movlw 'c'
call LCD_data
movlw'm'
call LCD_data
mullw PERL
movwf PERL
movlw d'34'
mullw PERH
addwf PERL,F
return
delay:
movlw d'450'
movwf COUNT1
D1:
movlw d'450'
movwf COUNT2
D2:
decfsz COUNT2, F
goto D2
decfsz COUNT1, F
goto D1
return
init_LCD:
bcf TRISC, 0 ; Set RS pin as output
bcf TRISC, 1 ; Set EN pin as output
clrf TRISD ; Set data bus pins as output
call delay
movlw b'00000001' ; Clear display
call LCD_cmd ; Send command
call delay
movlw b'00110000' ; Function set: 8-bit mode, 2-line display, 5x8 font
call LCD_cmd ; Send command
call delay
movlw b'00001100' ; Display control: Display on, cursor off, blink off
call LCD_cmd ; Send command
call delay
movlw b'00000110' ; Entry mode set: Increment cursor position, no display shift
call LCD_cmd ; Send command
call delay
movlw 'd' ; Send character 'A' to LCD
call LCD_data
movlw 'i' ; Send character 'B' to LCD
call LCD_data
movlw 's' ; Send character 'B' to LCD
call LCD_data
movlw 't' ; Send character 'B' to LCD
call LCD_data
movlw 'a' ; Send character 'B' to LCD
call LCD_data
movlw 'n' ; Send character 'B' to LCD
call LCD_data
movlw 'c' ; Send character 'B' to LCD
call LCD_data
movlw 'e' ; Send character 'B' to LCD
call LCD_data
; movlw b'11000000' ; Set cursor to second line
; call LCD_cmd
movlw ':'
call LCD_data
return
; Send command to LCD
LCD_cmd:
bcf PORTC,0 ; Set RS low for command mode
movwf PORTD ; Send command to data bus
bsf PORTC,1 ; Pulse EN pin high
call delay
bcf PORTC,1 ; Pulse EN pin low
return
; Send data to LCD
LCD_data:
bsf PORTC,0 ; Set RS high for data mode
movwf PORTD ; Send data to data bus
bsf PORTC,1 ; Pulse EN pin high
call delay
bcf PORTC,1 ; Pulse EN pin low
return
; Delay function
; Assume binary value is stored in register W
; Assume output will be stored in buffer starting at address 0x20
END
