Hey!
I'm working on a project using a PIC18F4550, I'm trying to measure distances with a HC-SR04 sensor and change frecuency of PWM , I have to trig a 10us pulse to the sensor, and I receive a pulse back from the echo. Wider the pulse, longer the distance. I'm trying to use interrupts to start counting with Timer0 the time that echo is '1'. The problem here, is that I can't measure the back pulse. I can't get into the interrupt succesfully and the timer doens't count what I need.
On the interrupt I write on PR2 register to change frecuency of PWM, but I haven't succeded yet. I already sent 10us pulses and I received an echo, but I haven't been able to use the timer properly.
I hope you can help me!
Here's my code.
I'm working on a project using a PIC18F4550, I'm trying to measure distances with a HC-SR04 sensor and change frecuency of PWM , I have to trig a 10us pulse to the sensor, and I receive a pulse back from the echo. Wider the pulse, longer the distance. I'm trying to use interrupts to start counting with Timer0 the time that echo is '1'. The problem here, is that I can't measure the back pulse. I can't get into the interrupt succesfully and the timer doens't count what I need.
On the interrupt I write on PR2 register to change frecuency of PWM, but I haven't succeded yet. I already sent 10us pulses and I received an echo, but I haven't been able to use the timer properly.
I hope you can help me!
Here's my code.
Code:
LIST P=18F4550
#include p18f4550.inc ; Include register definition file
CONFIG WDT = OFF
CONFIG MCLRE = ON
CONFIG DEBUG = ON
CONFIG LVP = OFF
CONFIG FOSC = XT_XT
CBLOCK 0x080
D1 ;variable usada para salvar contexto
D2
ENDC
org 0x0000
goto Inicio
org 0x0008
goto INTERRUPCION
;Puertos
Inicio
CLRF PORTB
movlw b'00001111'
movwf ADCON1
BSF TRISB,7 ; RA0 AS INPUT (ECHOIN)
BCF TRISA,0 ; RA1 AS OUTPUT (TRIGGER)
CLRF TRISC
movlw b'01000111'
movwf T0CON
;Interrupciones
bsf INTCON, GIE
bsf INTCON, RBIE
bcf INTCON, RBIF
; Configuracion PWM
MOVLW b'00000110'; BIT 2 Activar
MOVWF T2CON
MOVLW b'00011100'
MOVWF CCP1CON
MOVLW d'30'
MOVWF CCPR1L
TRIGGER; CREADOR DE PULSO DE 10US
BSF PORTA,0
nop
nop
nop
nop
nop
nop
nop
nop
nop
BCF PORTA,0
CALL DELAY60MS; PARA NO CREAR PULSOS EN MENOS DE 50MS
goto TRIGGER
INTERRUPCION
bsf T1CON, TMR0ON
INTERRUPCION_2
btfsc PORTB,7
goto INTERRUPCION_2
bcf T1CON, TMR0ON
movwf TMR0L
movlw PR2
bcf INTCON, RBIF
clrf TMR0L
retfie
DELAY60MS
MOVLW D'223'
MOVWF D1
MOVLW D'65'
MOVWF D2
DELAY_1
DECFSZ D1
GOTO DELAY_1
DECFSZ D2
GOTO DELAY_1
RETURN
END
