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$ cat ultrasonic_1.py

#!/usr/bin/python

#+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

#|R|a|s|p|b|e|r|r|y|P|i|-|S|p|y|.|c|o|.|u|k|

#+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

#

# ultrasonic_1.py

# Measure distance using an ultrasonic module

#

# Author : Matt Hawkins

# Date   : 09/01/2013

# -----------------------

# Import required Python libraries

import time

import RPi.GPIO as GPIO

# Use BCM GPIO references

# instead of physical pin numbers

GPIO.setmode(GPIO.BCM)

# Define GPIO to use on Pi

GPIO_TRIGGER = 18

GPIO_ECHO    = 18

print "Ultrasonic Measurement"

# Set pins as output and input

GPIO.setup(GPIO_TRIGGER,GPIO.OUT)  # Trigger

# Set trigger to False (Low)

GPIO.output(GPIO_TRIGGER, False)

# Allow module to settle

time.sleep(0.5)

# Send 10us pulse to trigger

GPIO.output(GPIO_TRIGGER, True)

time.sleep(0.00001)

GPIO.output(GPIO_TRIGGER, False)

start = time.time()

GPIO.setup(GPIO_ECHO,GPIO.IN)      # Echo

while GPIO.input(GPIO_ECHO)==0:

  start = time.time()

while GPIO.input(GPIO_ECHO)==1:

  stop = time.time()

# Calculate pulse length

elapsed = stop-start

# Distance pulse travelled in that time is time

# multiplied by the speed of sound (cm/s)

distance = elapsed * 34300

# That was the distance there and back so halve the value

distance = distance / 2

print "Distance : %.1f" % distance

# Reset GPIO settings

GPIO.cleanup() 

pi@raspberrypi ~/src/sonic $ sudo python ultrasonic_1.py

Ultrasonic Measurement

Distance : 154.8

pi@raspberrypi ~/src/sonic $ sudo python ultrasonic_1.py

Ultrasonic Measurement

Distance : 3.0

pi@raspberrypi ~/src/sonic $ sudo python ultrasonic_1.py

Ultrasonic Measurement

Distance : 9.1

pi@raspberrypi ~/src/sonic $ sudo python ultrasonic_1.py

Ultrasonic Measurement

Distance : 26.3 

#include <stdio.h>

int printf(const char *format, ...);

int fprintf(FILE *stream, const char *format, ...);

int sprintf(char *str, const char *format, ...);

int snprintf(char *str, size_t size, const char *format, ...);

#include <stdarg.h>

int vprintf(const char *format, va_list ap);

int vfprintf(FILE *stream, const char *format, va_list ap);

int vsprintf(char *str, const char *format, va_list ap);

int vsnprintf(char *str, size_t size, const char *format, va_list ap);

[링크 : http://linux.die.net/man/3/vsprintf] 

/*

 *  dht11.c:

 * Simple test program to test the wiringPi functions

 * DHT11 test

 */

#include <wiringPi.h>

#include <stdio.h>

#include <stdlib.h>

#include <stdint.h>

#define MAXTIMINGS 85

#define DHTPIN 7

int dht11_dat[5] = { 0, 0, 0, 0, 0 };

void read_dht11_dat()

{

uint8_t laststate = HIGH;

uint8_t counter = 0;

uint8_t j = 0, i;

float f; /* fahrenheit */

dht11_dat[0] = dht11_dat[1] = dht11_dat[2] = dht11_dat[3] = dht11_dat[4] = 0;

/* pull pin down for 18 milliseconds */

pinMode( DHTPIN, OUTPUT );

digitalWrite( DHTPIN, LOW );

delay( 18 );

/* then pull it up for 40 microseconds */

digitalWrite( DHTPIN, HIGH );

delayMicroseconds( 40 );

/* prepare to read the pin */

pinMode( DHTPIN, INPUT );

/* detect change and read data */

for ( i = 0; i < MAXTIMINGS; i++ )

{

counter = 0;

while ( digitalRead( DHTPIN ) == laststate )

{

counter++;

delayMicroseconds( 1 );

if ( counter == 255 )

{

break;

}

}

laststate = digitalRead( DHTPIN );

if ( counter == 255 )

break;

/* ignore first 3 transitions */

if ( (i >= 4) && (i % 2 == 0) )

{

/* shove each bit into the storage bytes */

dht11_dat[j / 8] <<= 1;

if ( counter > 16 )

dht11_dat[j / 8] |= 1;

j++;

}

}

/*

 * check we read 40 bits (8bit x 5 ) + verify checksum in the last byte

 * print it out if data is good

 */

if ( (j >= 40) &&

     (dht11_dat[4] == ( (dht11_dat[0] + dht11_dat[1] + dht11_dat[2] + dht11_dat[3]) & 0xFF) ) )

{

f = dht11_dat[2] * 9. / 5. + 32;

printf( "Humidity = %d.%d %% Temperature = %d.%d *C (%.1f *F)\n",

dht11_dat[0], dht11_dat[1], dht11_dat[2], dht11_dat[3], f );

}else  {

printf( "Data not good, skip\n" );

}

}

int main( void )

{

printf( "Raspberry Pi wiringPi DHT11 Temperature test program\n" );

if ( wiringPiSetup() == -1 )

exit( 1 );

while ( 1 )

{

read_dht11_dat();

delay( 1000 ); /* wait 1sec to refresh */

}

return(0);

}

[링크 : http://www.uugear.com/portfolio/dht11-humidity-temperature-sensor-module/] 

$ gcc dht11.c -lwiringPi

$ sudo ./a.out

Raspberry Pi wiringPi DHT11 Temperature test program

Humidity = 63.0 % Temperature = 26.0 *C (78.8 *F)

Data not good, skip

...

Humidity = 85.0 % Temperature = 30.0 *C (86.0 *F)

...