Greyjo
Newbie level 2
Hello,
I'm trying to build an ultrasonic distance meter by using 16f877a. I can transmit 40kHz signal from an external oscillator and get the
reflected signal with no problem. However, when i try to transmit a signal by setting the output pin (C1 at the program) 'high' for about
200us to activate oscillator and wait for the reflected signal, program stucks at 'while(input(echo)) {}' loop which indicates no signal
detected (constant 'high'=no signal). I'm using LM311 comparator, and its output is directly connected to the microcontroller's input pin
mentioned as 'echo'. Btw, signal detection can be observed from the comparator's output with a square wave (low=signal detected).
The other parts of the circuit and program is working well. I haven't been able to figure out the problem since it's also working quite good
on proteus simulation. This is my first work with microcontollers and i cannot find the error here. Can anyone give me some advice?
Sorry for long text
I'm trying to build an ultrasonic distance meter by using 16f877a. I can transmit 40kHz signal from an external oscillator and get the
reflected signal with no problem. However, when i try to transmit a signal by setting the output pin (C1 at the program) 'high' for about
200us to activate oscillator and wait for the reflected signal, program stucks at 'while(input(echo)) {}' loop which indicates no signal
detected (constant 'high'=no signal). I'm using LM311 comparator, and its output is directly connected to the microcontroller's input pin
mentioned as 'echo'. Btw, signal detection can be observed from the comparator's output with a square wave (low=signal detected).
Code:
#include <16F877A.h>
#device adc=8
#FUSES NOWDT, HS, NOPUT, PROTECT, NOBROWNOUT, NOLVP, NOCPD, NOWRT, NODEBUG
#use delay(clock=20000000)
#use fast_io(b)
#use fast_io(c)
#define trig PIN_C1
#define echo PIN_C0
#define use_portb_lcd TRUE
#include <lcd.c>
int16 distance, time;
void main()
{
setup_adc_ports(NO_ANALOGS);
setup_adc(ADC_OFF);
setup_psp(PSP_DISABLED);
setup_spi(SPI_SS_DISABLED);
setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1);
setup_timer_1(T1_INTERNAL|T1_DIV_BY_1);
setup_timer_2(T2_DISABLED,0,1);
set_tris_c(0x01);
set_tris_b(0x00);
lcd_init();
printf(LCD_PUTC, "\f TEST");
while(true)
{
output_high(PIN_C1); //starting the transmission
delay_us(200);
output_low(PIN_C1);
set_timer1(0); // no interrupts used, timer1's current value should be the time passed to calculate distance.
while(input(echo)) // echo (C0) , the input which is waiting for square wave to detect
{}
time=(get_timer1()/5);
distance=(time*0.0341)/2 ;
printf(LCD_PUTC, "\fTime:%Lu us\nDistance =%Lu cm",time,distance);
}
}The other parts of the circuit and program is working well. I haven't been able to figure out the problem since it's also working quite good
on proteus simulation. This is my first work with microcontollers and i cannot find the error here. Can anyone give me some advice?
Sorry for long text