Hi! I need some help here with my code. I'm trying to code DHT11 Sensor, pH Level Sensor and LCD Display (ST7920) for my project the day after tomorrow!
The problem is when I try to compile it, there are too many errors in my code. 
I use Arduino Uno to build my project. Here is the code:
#include <U8g2lib.h>
#include <U8x8lib.h>
#include "dht.h"
#include "u8g2lib.h"
#define DHT11_PIN 7 // what digital pin we're connected t
#define DHTTYPE DHT11
#define LDR_PIN A3 // The LDR is connected to the analog 3 pin
#define PH_PIN A5
#define GROW_LIGHT 6
#define FOG_PUMP 5
int LightLevel ;
int pH ;
DHT dht (DHT11_PIN, DHTTYPE); // These are the instances of DHT11
// Here will be the code for the pattern of the logo
U8GLIB_ST7920_128X64 u8g(4, 12, 6, U8G_PIN_NONE);
bool first;
float hum = 0.0;
double T = 0.0;
void dht_test (float * humPerc);
void setup (void) {
pinMode (GROW_LIGHT, OUTPUT);
pinMode (FOG_PUMP, OUTPUT);
digitalWrite (GROW_LIGHT, HIGH);
// Here is the intro of the LCD Display
first = true;
// assign default colour value
U8GLIB_ST7920_128X64 u8g(4, 12, 6, U8G_PIN_NONE);
if ( u8g.getMode() == U8G_MODE_R3G3B2 ) {
u8g.setColorIndex (255); // WHITE
}
else if ( u8g.getMode() == U8G_MODE_GRAY2BIT ) {
u8g.setHiColorIndex (3); // MAX INTENSITY
}
else if ( u8g.getMode() == U8G_MODE_BW ) {
u8g.setHiColorIndex (1); // PIXEL ON
}
else if ( u8g.getMode() == U8G_MODE_HICOLOR ) {
u8g.setHiColorByRGB (255,255,255);
}
}
void RefreshDisplay(float * humPerc, double *T, int *WL, int *LL, int *pH_value) {
u8g.setFont(u8g_font_fub11);
u8g.setFontRefHeightExtendedText();
u8g.setDefaultForegroundColor();
u8g.setFontPosTop();
u8g.drawStr( 4, 0, "Hum%");
u8g.setPrintPos( 68, 0);
u8g.print( *humPerc);
u8g.drawStr( 4, 15, "Temp");
u8g.setPrintPos( 68, 15);
u8g.print( *T);
u8g.drawStr( 4, 30, "Wlvl");
if (*WL == 0){
u8g.drawStr (68, 30,"EMPTY!");
digitalWrite (FOG_PUMP, LOW);
}
else{
if (*WL < 800)
u8g.drawStr (68, 30,"LOW");
else {
digitalWrite(FOG_PUMP, HIGH);
u8g.drawStr (68, 30,"HIGH");
}
}
if (*LL < 100) {
u8g.drawStr (68, 45,"Dark");
} else if (*LL < 200) {
u8g.drawStr (68, 45,"Dim");
} else if (*LL < 500) {
u8g.drawStr (68, 45, "Light");
} else if (*LL < 800) {
u8g.drawStr (68, 45,"Bright");
} else {
u8g.drawStr (68, 45,"2Bright");
}
double voltage = 5.0 / 1024.0 * (*pH_value);
float Po = 7 + ((2.5 - voltage) / 0.18);
u8g.drawStr (4, 45,"pH");
u8g.setPrintPos( 28, 45);
u8g.print( Po);
}
void loop(void) {
LightLevel = analogRead(LDR_PIN);
pH = analogRead (PH_PIN);
char status;
int chk = DHT.read11(DHT11_PIN);
hum = DHT.humidity;
dht_test(&hum);
if(first)
{
first = false;
}
}
void dht_test(float * humPerc) {
// Wait a few seconds between measurements.
delay(1000);
}
Here are the error messages:
Arduino: 1.8.9 (Windows 10), Board: "Arduino/Genuino Uno"
"C:\\Users\\Acer\\AppData\\Local\\Temp\\arduino_build_467446\\sketch\\Final_code.ino.cpp" -o "C:\\Users\\Acer\\AppData\\Local\\Temp\\arduino_build_467446\\sketch\\Final_code.ino.cpp.o"
Final_code:14:1: error: 'DHT' does not name a type
DHT dht (DHT11_PIN, DHTTYPE); // These are the instances of DHT11
^
Final_code:17:1: error: 'U8GLIB_ST7920_128X64' does not name a type
U8GLIB_ST7920_128X64 u8g(4, 12, 6, U8G_PIN_NONE);
^
C:\Users\Acer\AppData\Local\Temp\arduino_modified_sketch_229924\Final_code.ino: In function 'void setup()':
Final_code:32:1: error: 'U8GLIB_ST7920_128X64' was not declared in this scope
U8GLIB_ST7920_128X64 u8g(4, 12, 6, U8G_PIN_NONE);
^
Final_code:33:8: error: 'u8g' was not declared in this scope
if ( u8g.getMode() == U8G_MODE_R3G3B2 ) {
^
Final_code:33:25: error: 'U8G_MODE_R3G3B2' was not declared in this scope
if ( u8g.getMode() == U8G_MODE_R3G3B2 ) {
^
Final_code:36:30: error: 'U8G_MODE_GRAY2BIT' was not declared in this scope
else if ( u8g.getMode() == U8G_MODE_GRAY2BIT ) {
^
Final_code:39:30: error: 'U8G_MODE_BW' was not declared in this scope
else if ( u8g.getMode() == U8G_MODE_BW ) {
^
Final_code:42:30: error: 'U8G_MODE_HICOLOR' was not declared in this scope
else if ( u8g.getMode() == U8G_MODE_HICOLOR ) {
^
C:\Users\Acer\AppData\Local\Temp\arduino_modified_sketch_229924\Final_code.ino: In function 'void RefreshDisplay(float*, double*, int*, int*, int*)':
Final_code:48:3: error: 'u8g' was not declared in this scope
u8g.setFont(u8g_font_fub11);
^
Final_code:48:15: error: 'u8g_font_fub11' was not declared in this scope
u8g.setFont(u8g_font_fub11);
^
C:\Users\Acer\AppData\Local\Temp\arduino_modified_sketch_229924\Final_code.ino: In function 'void loop()':
Final_code:96:11: error: 'DHT' was not declared in this scope
int chk = DHT.read11(DHT11_PIN);
^
Using library U8g2 at version 2.26.14 in folder: C:\Users\Acer\Documents\Arduino\libraries\U8g2
Using library DHT in folder: C:\Users\Acer\Documents\Arduino\libraries\DHT (legacy)
Using library SPI at version 1.0 in folder: C:\Program Files (x86)\Arduino\hardware\arduino\avr\libraries\SPI
Using library Wire at version 1.0 in folder: C:\Program Files (x86)\Arduino\hardware\arduino\avr\libraries\Wire
exit status 1
'DHT' does not name a type
There must be a simple solution to these errors. I'm new in learning Arduino. Any help is much appreciated!