root@raspberrypi2 ~/projects/interrupt_test # ls -l /sys/class/gpio/gpio25/
total 0
-rw-r--r-- 1 root root 4096 Apr  8 23:56 active_low
-rw-r--r-- 1 root root 4096 Apr  8 22:29 direction
-rw-r--r-- 1 root root 4096 Apr  8 22:29 edge
drwxr-xr-x 2 root root    0 Apr  8 23:56 power
lrwxrwxrwx 1 root root    0 Apr  8 23:56 subsystem -> ../../../../class/gpio
-rw-r--r-- 1 root root 4096 Apr  8 22:08 uevent
-rw-r--r-- 1 root root 4096 Apr  8 22:29 value
root@raspberrypi2 ~/projects/interrupt_test # 

#!/usr/bin/python

#
# based on code from lrvick and LiquidCrystal
# lrvic - https://github.com/lrvick/raspi-hd44780/blob/master/hd44780.py
# LiquidCrystal - https://github.com/arduino/Arduino/blob/master/libraries/LiquidCrystal/LiquidCrystal.cpp
#

from time import sleep
from datetime import datetime
from time import sleep

class Adafruit_CharLCD:

    # commands
    LCD_CLEARDISPLAY 		= 0x01
    LCD_RETURNHOME 		    = 0x02
    LCD_ENTRYMODESET 		= 0x04
    LCD_DISPLAYCONTROL 		= 0x08
    LCD_CURSORSHIFT 		= 0x10
    LCD_FUNCTIONSET 		= 0x20
    LCD_SETCGRAMADDR 		= 0x40
    LCD_SETDDRAMADDR 		= 0x80

    # flags for display entry mode
    LCD_ENTRYRIGHT 		= 0x00
    LCD_ENTRYLEFT 		= 0x02
    LCD_ENTRYSHIFTINCREMENT 	= 0x01
    LCD_ENTRYSHIFTDECREMENT 	= 0x00

    # flags for display on/off control
    LCD_DISPLAYON 		= 0x04
    LCD_DISPLAYOFF 		= 0x00
    LCD_CURSORON 		= 0x02
    LCD_CURSOROFF 		= 0x00
    LCD_BLINKON 		= 0x01
    LCD_BLINKOFF 		= 0x00

    # flags for display/cursor shift
    LCD_DISPLAYMOVE 		= 0x08
    LCD_CURSORMOVE 		= 0x00

    # flags for display/cursor shift
    LCD_DISPLAYMOVE 		= 0x08
    LCD_CURSORMOVE 		= 0x00
    LCD_MOVERIGHT 		= 0x04
    LCD_MOVELEFT 		= 0x00

    # flags for function set
    LCD_8BITMODE 		= 0x10
    LCD_4BITMODE 		= 0x00
    LCD_2LINE 			= 0x08
    LCD_1LINE 			= 0x00
    LCD_5x10DOTS 		= 0x04
    LCD_5x8DOTS 		= 0x00



    def __init__(self, pin_rs=8, pin_e=10, pins_db=[11,12,13,15], GPIO = None):
	# Emulate the old behavior of using RPi.GPIO if we haven't been given
	# an explicit GPIO interface to use
	if not GPIO:
	    import RPi.GPIO as GPIO
        GPIO.setwarnings(False)

   	self.GPIO = GPIO
        self.pin_rs = pin_rs
        self.pin_e = pin_e
        self.pins_db = pins_db

        self.GPIO.setmode(GPIO.BOARD)
        self.GPIO.setup(self.pin_e, GPIO.OUT)
        self.GPIO.setup(self.pin_rs, GPIO.OUT)

        for pin in self.pins_db:
            self.GPIO.setup(pin, GPIO.OUT)

	self.write4bits(0x33) # initialization
	self.write4bits(0x32) # initialization
	self.write4bits(0x28) # 2 line 5x7 matrix
	self.write4bits(0x0C) # turn cursor off 0x0E to enable cursor
	self.write4bits(0x06) # shift cursor right

	self.displaycontrol = self.LCD_DISPLAYON | self.LCD_CURSOROFF | self.LCD_BLINKOFF

	self.displayfunction = self.LCD_4BITMODE | self.LCD_1LINE | self.LCD_5x8DOTS
	self.displayfunction |= self.LCD_2LINE

	""" Initialize to default text direction (for romance languages) """
	self.displaymode =  self.LCD_ENTRYLEFT | self.LCD_ENTRYSHIFTDECREMENT
	self.write4bits(self.LCD_ENTRYMODESET | self.displaymode) #  set the entry mode

        self.clear()


    def begin(self, cols, lines):

	if (lines > 1):
		self.numlines = lines
    		self.displayfunction |= self.LCD_2LINE
		self.currline = 0


    def home(self):

	self.write4bits(self.LCD_RETURNHOME) # set cursor position to zero
	self.delayMicroseconds(3000) # this command takes a long time!
	

    def clear(self):

	self.write4bits(self.LCD_CLEARDISPLAY) # command to clear display
	self.delayMicroseconds(3000)	# 3000 microsecond sleep, clearing the display takes a long time


    def setCursor(self, col, row):

	self.row_offsets = [ 0x00, 0x40, 0x14, 0x54 ]

	if ( row > self.numlines ): 
		row = self.numlines - 1 # we count rows starting w/0

	self.write4bits(self.LCD_SETDDRAMADDR | (col + self.row_offsets[row]))


    def noDisplay(self): 
	""" Turn the display off (quickly) """

	self.displaycontrol &= ~self.LCD_DISPLAYON
	self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)


    def display(self):
	""" Turn the display on (quickly) """

	self.displaycontrol |= self.LCD_DISPLAYON
	self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)


    def noCursor(self):
	""" Turns the underline cursor on/off """

	self.displaycontrol &= ~self.LCD_CURSORON
	self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)


    def cursor(self):
	""" Cursor On """

	self.displaycontrol |= self.LCD_CURSORON
	self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)


    def noBlink(self):
	""" Turn on and off the blinking cursor """

	self.displaycontrol &= ~self.LCD_BLINKON
	self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)


    def noBlink(self):
	""" Turn on and off the blinking cursor """

	self.displaycontrol &= ~self.LCD_BLINKON
	self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)


    def DisplayLeft(self):
	""" These commands scroll the display without changing the RAM """

	self.write4bits(self.LCD_CURSORSHIFT | self.LCD_DISPLAYMOVE | self.LCD_MOVELEFT)


    def scrollDisplayRight(self):
	""" These commands scroll the display without changing the RAM """

	self.write4bits(self.LCD_CURSORSHIFT | self.LCD_DISPLAYMOVE | self.LCD_MOVERIGHT);


    def leftToRight(self):
	""" This is for text that flows Left to Right """

	self.displaymode |= self.LCD_ENTRYLEFT
	self.write4bits(self.LCD_ENTRYMODESET | self.displaymode);


    def rightToLeft(self):
	""" This is for text that flows Right to Left """
	self.displaymode &= ~self.LCD_ENTRYLEFT
	self.write4bits(self.LCD_ENTRYMODESET | self.displaymode)


    def autoscroll(self):
	""" This will 'right justify' text from the cursor """

	self.displaymode |= self.LCD_ENTRYSHIFTINCREMENT
	self.write4bits(self.LCD_ENTRYMODESET | self.displaymode)


    def noAutoscroll(self): 
	""" This will 'left justify' text from the cursor """

	self.displaymode &= ~self.LCD_ENTRYSHIFTINCREMENT
	self.write4bits(self.LCD_ENTRYMODESET | self.displaymode)


    def write4bits(self, bits, char_mode=False):
        """ Send command to LCD """

	self.delayMicroseconds(1000) # 1000 microsecond sleep

        bits=bin(bits)[2:].zfill(8)

        self.GPIO.output(self.pin_rs, char_mode)

        for pin in self.pins_db:
            self.GPIO.output(pin, False)

        for i in range(4):
            if bits[i] == "1":
                self.GPIO.output(self.pins_db[::-1][i], True)

	self.pulseEnable()

        for pin in self.pins_db:
            self.GPIO.output(pin, False)

        for i in range(4,8):
            if bits[i] == "1":
                self.GPIO.output(self.pins_db[::-1][i-4], True)

	self.pulseEnable()


    def delayMicroseconds(self, microseconds):
	seconds = microseconds / float(1000000)	# divide microseconds by 1 million for seconds
	sleep(seconds)


    def pulseEnable(self):
	self.GPIO.output(self.pin_e, False)
	self.delayMicroseconds(1)		# 1 microsecond pause - enable pulse must be > 450ns 
	self.GPIO.output(self.pin_e, True)
	self.delayMicroseconds(1)		# 1 microsecond pause - enable pulse must be > 450ns 
	self.GPIO.output(self.pin_e, False)
	self.delayMicroseconds(1)		# commands need > 37us to settle


    def message(self, text):
        """ Send string to LCD. Newline wraps to second line"""

        for char in text:
            if char == '\n':
                self.write4bits(0xC0) # next line
            else:
                self.write4bits(ord(char),True)


if __name__ == '__main__':

    lcd = Adafruit_CharLCD()
    lcd.noBlink()

    while True:
        sleep(1)
        lcd.clear()        
        lcd.message(datetime.now().strftime('  %I : %M : %S \n%a %b %d %Y'))
        

#include <wiringPi.h>  
#include <stdio.h>  
#include <stdlib.h>  
#include <stdint.h>  
#define MAX_TIME 85  
#define DHT11PIN 7  

int dht11_val[5]={0,0,0,0,0};  
int errors=0;

  
void dht11_read_val()  
{  
  uint8_t lststate=HIGH;  
  uint8_t counter=0;  
  uint8_t j=0,i;  
  float farenheit;  
  for(i=0;i<5;i++)  
     dht11_val[i]=0;  
  pinMode(DHT11PIN,OUTPUT);  
  digitalWrite(DHT11PIN,LOW);  
  delay(18);  
  digitalWrite(DHT11PIN,HIGH);  
  delayMicroseconds(40);  
  pinMode(DHT11PIN,INPUT);  
  for(i=0;i<MAX_TIME;i++)  
  {  
    counter=0;  
    while(digitalRead(DHT11PIN)==lststate){  
      counter++;  
      delayMicroseconds(1);  
      if(counter==255)  
        break;  
    }  
    lststate=digitalRead(DHT11PIN);  
    if(counter==255)  
       break;  
    // top 3 transistions are ignored  
    if((i>=4)&&(i%2==0)){  
      dht11_val[j/8]<<=1;  
      if(counter>16)  
        dht11_val[j/8]|=1;  
      j++;  
    }  
  }  
  // verify cheksum and print the verified data  
  if((j>=40)&&(dht11_val[4]==((dht11_val[0]+dht11_val[1]+dht11_val[2]+dht11_val[3])& 0xFF)))  
  {  
    //farenheit=dht11_val[2]*9./5.+32;  
    printf("%d.%d\t%d.%d\n", dht11_val[0],dht11_val[1],dht11_val[2],dht11_val[3]);    
    exit(1);
  }  
  else { 
    errors = errors + 1;
    if (errors > 5) {
      printf("0.0\t0.0");
      exit(2);
    }
  }
}  
  
int main(void)  
{  
  if(wiringPiSetup()==-1)  
    exit(1);  
  while(1)  
  {  
     dht11_read_val();  
     delay(3000);  
  }  
  return 0;  
}  

git clone https://github.com/WiringPi/WiringPi
cd WiringPi/wiringPi
sudo make install	

#include <wiringPi.h>
#include <stdio.h>
#include <stdlib.h>

int main (int argc, char* argv[])
{
	int pinNumber = 4;
	if (-1 == wiringPiSetup()) {
		printf("failed to setup wiringPi");
		return 1;
	}	
	pinMode(pinNumber, OUTPUT);
	digitalWrite(pinNumber, 1);
	delay(200);
	digitalWrite(pinNumber, 0);
	delay(200);
	return 0;	
}

   useradd hugo
   passwd hugo
   mkdir /home/hugo
   chown hugo:hugo /home/hugo   
   pacman -S sudo
   visudo   
   

    hugo ALL=(ALL) NOPASSWD: ALL

    [root@raspberrypi2 ~]# lsblk -o name,kname,uuid   
    NAME        KNAME     UUID
    sda         sda       001B-9622
    mmcblk0     mmcblk0   
    ├─mmcblk0p1 mmcblk0p1 44C8-CEF1
    └─mmcblk0p2 mmcblk0p2 fcee8534-f5f0-42ee-83ac-f943f878ee67
    
    mkdir /mnt/usb
    mount /dev/sda /mnt/usb 
    或 
    mount -U 001B-9622 /mnt/usb