diff --git a/Code/C_Code/05.1.1_ColorfulLED/ColorfulLED.c b/Code/C_Code/05.1.1_ColorfulLED/ColorfulLED.c
index 92ffe82..7722654 100644
--- a/Code/C_Code/05.1.1_ColorfulLED/ColorfulLED.c
+++ b/Code/C_Code/05.1.1_ColorfulLED/ColorfulLED.c
@@ -42,7 +42,7 @@ int main(void)
 		b=random()%100;  //get a random in (0,100)
 		setLedColor(r,g,b);//set random as the duty cycle value 
 		printf("r=%d,  g=%d,  b=%d \n",r,g,b);
-		delay(300);
+		delay(1000);
 	}
 	return 0;
 }
diff --git a/Code/C_Code/20.1.1_I2CLCD1602/I2CLCD1602.c b/Code/C_Code/20.1.1_I2CLCD1602/I2CLCD1602.c
index 4ab4e23..0431a72 100644
--- a/Code/C_Code/20.1.1_I2CLCD1602/I2CLCD1602.c
+++ b/Code/C_Code/20.1.1_I2CLCD1602/I2CLCD1602.c
@@ -2,17 +2,17 @@
 * Filename    : I2CLCD1602.c
 * Description : Use the LCD display data
 * Author      : www.freenove.com
-* modification: 2019/12/27
+* modification: 2020/07/23
 **********************************************************************/
 #include <stdlib.h>
 #include <stdio.h>
 #include <wiringPi.h>
+#include <wiringPiI2C.h>
 #include <pcf8574.h>
 #include <lcd.h>
 #include <time.h>
 
-//#define pcf8574_address 0x27        // default I2C address of Pcf8574
-#define pcf8574_address 0x3F        // default I2C address of Pcf8574A
+int pcf8574_address = 0x27;        // PCF8574T:0x27, PCF8574AT:0x3F
 #define BASE 64         // BASE any number above 64
 //Define the output pins of the PCF8574, which are directly connected to the LCD1602 pin.
 #define RS      BASE+0
@@ -45,7 +45,24 @@ void printDataTime(){//used to print system time
     timeinfo = localtime(&rawtime);//convert to local time
     printf("%s \n",asctime(timeinfo));
     lcdPosition(lcdhd,0,1);// set the LCD cursor position to (0,1) 
-    lcdPrintf(lcdhd,"Time: %02d:%02d:%02d", timeinfo->tm_hour, timeinfo->tm_min, timeinfo->tm_sec); //Display system time on LCD
+    lcdPrintf(lcdhd,"Time:%02d:%02d:%02d",timeinfo->tm_hour,timeinfo->tm_min,timeinfo->tm_sec); //Display system time on LCD
+}
+int detectI2C(int addr){
+    int _fd = wiringPiI2CSetup (addr);   
+    if (_fd < 0){		
+        printf("Error address : 0x%x \n",addr);
+        return 0 ;
+    } 
+    else{	
+        if(wiringPiI2CWrite(_fd,0) < 0){
+            printf("Not found device in address 0x%x \n",addr);
+            return 0;
+        }
+        else{
+            printf("Found device in address 0x%x \n",addr);
+            return 1 ;
+        }
+    }
 }
 int main(void){
     int i;
@@ -53,7 +70,16 @@ int main(void){
     printf("Program is starting ...\n");
 
     wiringPiSetup();  
-      
+    if(detectI2C(0x27)){
+        pcf8574_address = 0x27;
+    }else if(detectI2C(0x3F)){
+        pcf8574_address = 0x3F;
+    }else{
+        printf("No correct I2C address found, \n"
+        "Please use command 'i2cdetect -y 1' to check the I2C address! \n"
+        "Program Exit. \n");
+        return -1;
+    }
     pcf8574Setup(BASE,pcf8574_address);//initialize PCF8574
     for(i=0;i<8;i++){
         pinMode(BASE+i,OUTPUT);     //set PCF8574 port to output mode
diff --git a/Code/Python_Code/05.1.1_ColorfulLED/ColorfulLED.py b/Code/Python_Code/05.1.1_ColorfulLED/ColorfulLED.py
index 7d971b7..e512668 100644
--- a/Code/Python_Code/05.1.1_ColorfulLED/ColorfulLED.py
+++ b/Code/Python_Code/05.1.1_ColorfulLED/ColorfulLED.py
@@ -35,7 +35,7 @@ def loop():
         b=random.randint(0,100)
         setColor(r,g,b)          #set random as a duty cycle value 
         print ('r=%d, g=%d, b=%d ' %(r ,g, b))
-        time.sleep(0.3)
+        time.sleep(1)
         
 def destroy():
     pwmRed.stop()
diff --git a/Tutorial.pdf b/Tutorial.pdf
index 21476e4..e6677c8 100644
Binary files a/Tutorial.pdf and b/Tutorial.pdf differ