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--- en:examples:sensor:ultrasonic [2009/04/01 11:52] – raivo.sell
+++ en:examples:sensor:ultrasonic [2010/03/29 11:06] (current) – removed raivo.sell
@@ Line 1: / Line 1: @@
-====== Ultrasonic distance measure ======
-SRF04 example
-Trigger (blue wire) is connected to PB2
-Echo (yellow wire) is connected to PB3
-Red and Black wires are +5 V supply
-{{examples:sensor:ultrasonic.jpg?500|}}
-<code c>
-//
-// SFR04 ultrasonic distance measuring
-//
-// Mikk Leini
-//
-// 2009
-//
-// Include avrlibc
-#include <avr/io.h>
-#include <avr/interrupt.h>
-#include <util/delay.h>
-// Include common library
-#include "pinops.h"
-// Configuration
-#define INTEGRATION_STEP 5
-// Math operations
-#define MIN(a, b)   ((a) < (b) ? (a) : (b))
-#define MAX(a, b)   ((a) > (b) ? (a) : (b))
-#define INTEGRATE(value, new_value, n)  value = (value * (n - 1) + new_value) / n;
-// Configure pins
-#define SEGMENT_DISPLAY_LATCH      PORTPIN(G, 2)
-#define SEGMENT_DISPLAY_DATA_OUT   PORTPIN(C, 6)
-#define SEGMENT_DISPLAY_CLOCK      PORTPIN(C, 7)
-#define LEDR                       PORTPIN(C, 5)
-#define US_TRIGGER                 PORTPIN(B, 2) // blue
-#define US_ECHO                    PORTPIN(B, 3) // yellow
-// Ultrasonic data structure
-struct
-{
-	unsigned char state;
-	unsigned long front;
-	unsigned short result;
-} ultrasonic;
-// 16 bit timestamp
-volatile unsigned long timestamp = 0;
-//
-// 7 segment display initialization
-//
-void segment_diplay_init(void)
-{
-	// Set latch, data out and clock pins as output
-	setup_output_pin(SEGMENT_DISPLAY_LATCH);
-	setup_output_pin(SEGMENT_DISPLAY_DATA_OUT);
-	setup_output_pin(SEGMENT_DISPLAY_CLOCK);
-}
-//
-// Digit writing to 7 segment display
-//
-void segment_display_write(unsigned char digit)
-{
-	unsigned char map;
-	// Decimal to segment map
-	switch (digit)
-	{
-		case 0 : map = 0b00111111; break; // Every bit corresponds to one segment
-		case 1 : map = 0b00000110; break; // "1"
-		case 2 : map = 0b01011011; break; // "2"
-		case 3 : map = 0b01001111; break; // "3" and so on
-		case 4 : map = 0b01100110; break;
-		case 5 : map = 0b01101101; break;
-		case 6 : map = 0b01111100; break;
-		case 7 : map = 0b00000111; break;
-		case 8 : map = 0b01111111; break;
-		case 9 : map = 0b01100111; break;
-		default: map = 0b01111001;        // E like Error
-	}
-	// Latch low
-	clear_pin(SEGMENT_DISPLAY_LATCH);
-	// Send every bit in the byte. MSB (most significant bit) first.
-	for (signed char i = 7; i >= 0; i--)
-	{
-		// If bit is set, sets the data out pin, otherwise not
-		set_pin_to(SEGMENT_DISPLAY_DATA_OUT, IS_BIT_SET(map, i));
-		// Clock high for certain period
-		set_pin(SEGMENT_DISPLAY_CLOCK)
-		_delay_us(1);
-		// Clock low for certain period
-		clear_pin(SEGMENT_DISPLAY_CLOCK)
-		_delay_us(1);
-	}
-	// Latch high
-	set_pin(SEGMENT_DISPLAY_LATCH);
-}
-//
-// 0.1ms clock Timer1
-//
-void clock_init(void)
-{
-	// Fast PWM, Top = ICR, Prescaler = 1
-	TCCR1A = BIT(WGM11);
-	TCCR1B = BIT(WGM13) | BIT(WGM12) | BIT(CS10);
-	// Top = 1475
-	// Clock = 14.745600 Mhz / 1475 = ~10 kHz
-	// Period = 1 / Clock = 0.1 ms
-	ICR1 = 1475;
-	// Enable overflow interrupt
-	TIMSK = BIT(TOIE1);
-}
-//
-// Delay
-// Time in 0.1 of milliseconds
-//
-void delay(unsigned int time)
-{
-	unsigned long end_time, temporary = 0;
-	// Interrupt safe timestamp waiting
-	cli();
-	end_time = timestamp + time;
-	sei();
-	while (temporary < end_time)
-	{
-		cli();
-		temporary = timestamp;
-		sei();
-		asm volatile ("nop");
-	}
-}
-//
-// Timer1 overflow interrupt
-//
-ISR(TIMER1_OVF_vect)
-{
-	timestamp++;
-}
-//
-// Ultrasonic initialization
-//
-void ultrasonic_init(void)
-{
-	// Initial state
-	ultrasonic.state  = 0;
-	ultrasonic.result = 0;
-	// Setup pins
-	setup_output_pin(US_TRIGGER);
-	setup_input_pin(US_ECHO);
-	// External interrupt on any logical change
-	EICRB = BIT(ISC40);
-	// Enable external interrupt 4
-	EIMSK = BIT(INT4);
-}
-//
-// Trigger ultrasonic pulse
-//
-void ultrasonic_trigger(void)
-{
-	// Cannot trigger when listening
-	if (ultrasonic.state > 0)
-		return;
-	// Trigger ultrasonic pulse
-	ultrasonic.state = 1;
-	set_pin(US_TRIGGER);
-	delay(1);
-	clear_pin(US_TRIGGER);
-}
-//
-// External interrupt - on echo pulse
-//
-ISR(INT4_vect)
-{
-	unsigned char b;
-	get_pin_value(US_ECHO, b);
-	// Rising edge ?
-	if (b && (ultrasonic.state == 1))
-	{
-		ultrasonic.front = timestamp;
-		ultrasonic.state = 2;
-	}
-	// Falling edge ?
-	else if (!b && (ultrasonic.state == 2))
-	{
-		ultrasonic.result = timestamp - ultrasonic.front;
-		ultrasonic.state = 0;
-	}
-}
-//
-// Get ultrasonic result
-//
-unsigned short ultrasonic_getresult(void)
-{
-	unsigned short result;
-	// Interrupt safe result reading
-	cli();
-	result = ultrasonic.result;
-	sei();
-	asm volatile ("nop");
-	return result;
-}
-//
-// Program entrance function
-//
-int main(void)
-{
-	volatile unsigned short lowValue  = 0xFFFF;
-	volatile unsigned short highValue = 0x0000;
-	volatile unsigned short value = 0;
-	volatile unsigned char relativeValue;
-	// Initializing
-	clock_init();
-	ultrasonic_init();
-	segment_diplay_init();
-	setup_output_pin(LEDR);
-	// Enable global interrupts
-	sei();
- 	// Endless loop
-	while (1)
-	{
-		// Blink LED every second
-		cli();
-		set_pin_to(LEDR, (timestamp % 10000) > 1000);
-		sei();
-		// Constantly try triggering ultrasonic pulses
-		ultrasonic_trigger();
-		// Read ultrasonic result
-		INTEGRATE(value, ultrasonic_getresult(), INTEGRATION_STEP);
-		// Check for new lower limit
-		lowValue = MIN(lowValue, value);
-		// Check for new higher limit
-		highValue = MAX(highValue, value);
-		// Calculate relative value
-		// Range from lowValue to highValue is converted to 0 to 9
-		relativeValue = 9 * (value - lowValue) / (highValue - lowValue);
-		// Write digit
-		segment_display_write(relativeValue);
-		// Delay a while
-		delay(50);
-	}
-}
-</code>

en/examples/sensor/ultrasonic.1238586729.txt.gz · Last modified: 2020/07/20 09:00 (external edit)