SRF05 example

This example uses one pin mode of SRF05. Code is based on the slightly modifyed HomeLab library 1.03 ultrasonic_measure function. Example is intented for the ATmega128 controller module and Sensor module (v5).

#include <homelab/delay.h>
#include <homelab/module/lcd_gfx.h>
#include <homelab/timer.h>
#include "homelab/common.h"
#include "homelab/pin.h"
 
#define ULTRASONIC_SPEED_OF_SOUND    33000 // cm/s
 
//SRF05 1 pin mode
pin srf05 = PIN(F,3);
 
//external sensor selection (make sure that the resistor is monted on the RC socket)
pin ext_sensors = PIN(G, 0);
 
 
//////////////////////////// UH measure //////////////
 
unsigned short ultrasonic_measure(pin srf05)
{   
    // Pin setup
    pin_setup_output(srf05);
 
    // Set timer 3 to normal mode
    // with period of F_CPU / 8
    timer3_init_normal(TIMER3_PRESCALE_8);      
 
    // Create trigger pulse
    pin_set(srf05);
 
    // Reset timer
    timer3_overflow_flag_clear();
    timer3_set_value(0);    
 
    // Wait ~10 us
    while (timer3_get_value() < 18) {}
 
    // End trigger pulse
    pin_clear(srf05);
 
    //short delay
    sw_delay_ms(1);
 
    //set the pin as input
    pin_setup_input_with_pullup(srf05);
 
    // Wait for echo start
    while (!pin_get_value(srf05))
    {
        // Timeout ?
        if (timer3_overflow_flag_is_set())
        {
            return 0;
        }
    }
 
    // Reset timer again
    timer3_set_value(0);
 
    // Wait for echo end    
    while (pin_get_value(srf05))
    {
        // Timeout ?
        if (timer3_overflow_flag_is_set())
        {
            return 0;
        }
    }
 
    // Convert time to distance:
    //   distance = timer * (1 / (F_CPU / 8)) * speed / 2
    return (unsigned long)timer3_get_value() *
        ULTRASONIC_SPEED_OF_SOUND / (F_CPU / 4);
}
 
/////////////////////////   Main program  /////////////////////////////
 
int main(void)
{
    int dist;
    char text[16]; 
 
    //set external sensor
    pin_setup_output(ext_sensors); 
    pin_set(ext_sensors);
 
    // LCD init
    lcd_gfx_init();
    lcd_gfx_clear();
 
    while (true)
    {
        //Measure
        dist = ultrasonic_measure(srf05);
 
        //print to LCD
        sprintf(text,"Distance: %d cm",dist);
        lcd_gfx_goto_char_xy(0, 0);
        lcd_gfx_write_string(text);
 
        //0,5 s delay
        sw_delay_ms(50);
 
        //Clear LCD
        lcd_gfx_clear();
    }
}