I think you need to have a variable to indicate what the screen state is, so that when Setting mode is pressed for example, it stays in that state.
I also suggest putting code into functions, it will be easier to read and maintain.
ETA: It turns out you already have a variable to indicate the current screen. I think the problem with the buttons is not setting the "previous_xxx_state" variables.
Anyway, here is an updated sketch, you can compare the differences
#include <DHT.h>
#include<Wire.h>
#include <LiquidCrystal_I2C.h>
#define DHTPIN 2
#define DHTTYPE DHT22
#include "RTClib.h"
#include "customchar.h"
RTC_DS1307 RTC;
DHT dht(DHTPIN, DHTTYPE);
LiquidCrystal_I2C lcd(0x27, 16, 2);
// Define the variables for temperature and humidity
float hum;
float temp;
// Define the strings for temperature and humidity
char tempStr[6];
char humStr[5];
// Define the pins for the buttons
#define UP_PIN 3
#define DOWN_PIN 4
#define SAVE_PIN 5
#define SETTING_PIN 6
// Define the pins for the relay, the fan, and the LEDs
#define RELAY_PIN 7
#define FAN_PIN 8
#define LED1_PIN 9
#define LED2_PIN 10
#define LED3_PIN 11
// Define the values for the buttons
#define UP_VALUE 0
#define DOWN_VALUE 1
#define SAVE_VALUE 2
#define SETTING_VALUE 3
#define NONE_VALUE 4
// Define the variables for the settings
float temp_setting = 25.0; // default temperature setting
float hum_setting = 50.0; // default humidity setting
int day_setting = 21; // default day setting
int engine_setting = 5; // default engine setting
enum {Normal, Temperature, Humidity, Day, Engine} ;
int setting_mode = Normal; // 0 for normal mode, 1 for temperature mode, 2 for humidity mode, 3 for day mode, 4 for engine mode
// Define the variables for the button states
int up_state = 0;
int down_state = 0;
int save_state = 0;
int setting_state = 0;
int prev_up_state = 0;
int prev_down_state = 0;
int prev_save_state = 0;
int prev_setting_state = 0;
// Define the variables for the engine time and the days
unsigned long engine_time = 0; // the time when the engine last ran
unsigned long start_time = 0; // the time when the program started
int engine_interval = 3600000; // the interval between engine runs in milliseconds
int engine_duration = 60000; // the duration of engine runs in milliseconds
int day_count = 0; // the number of days passed
void setup() {
Wire.begin();
dht.begin();
lcd.init();
lcd.clear();
lcd.backlight();
lcd.setCursor(0, 0);
lcd.print(" H - Electro");
delay(2000);
lcd.clear();
RTC.begin(); // load the time from your computer.
lcd.createChar(0, TempChar);
lcd.createChar(1, HumChar);
lcd.createChar(2, Ochar);
// set up the button pins as inputs with pull-up resistors
pinMode(UP_PIN, INPUT_PULLUP);
pinMode(DOWN_PIN, INPUT_PULLUP);
pinMode(SAVE_PIN, INPUT_PULLUP);
pinMode(SETTING_PIN, INPUT_PULLUP);
// set up the relay, the fan, and the LED pins as outputs
pinMode(RELAY_PIN, OUTPUT);
pinMode(FAN_PIN, OUTPUT);
pinMode(LED1_PIN, OUTPUT);
pinMode(LED2_PIN, OUTPUT);
pinMode(LED3_PIN, OUTPUT);
// get the initial time
start_time = millis();
if (! RTC.isrunning()) {
lcd.setCursor(1, 1);
lcd.print("RTC is NOT work");// This will reflect the time that your sketch was compiled
RTC.adjust(DateTime(__DATE__, __TIME__));
}
}
void check_buttons (void)
{
// read the button states
up_state = digitalRead(UP_PIN);
down_state = digitalRead(DOWN_PIN);
save_state = digitalRead(SAVE_PIN);
setting_state = digitalRead(SETTING_PIN);
// check if any button is pressed
if (up_state == LOW || down_state == LOW || save_state == LOW || setting_state == LOW)
{
// clear the screen
lcd.clear();
// check which button is pressed and change the settings accordingly
if (setting_state == LOW && prev_setting_state == HIGH ) {
// switch to the next setting mode
setting_mode = (setting_mode + 1) % 5;
}
else if (up_state == LOW && prev_up_state == HIGH) {
// increase the current setting value
if (setting_mode == 1) {
temp_setting += 0.5;
}
else if (setting_mode == 2) {
hum_setting += 1.0;
}
else if (setting_mode == 3) {
day_setting += 1;
}
else if (setting_mode == 4) {
engine_setting = (engine_setting % 9) + 1;
}
}
else if (down_state == LOW && prev_down_state == HIGH) {
// decrease the current setting value
if (setting_mode == 1) {
temp_setting -= 0.5;
}
else if (setting_mode == 2) {
hum_setting -= 1.0;
}
else if (setting_mode == 3) {
day_setting -= 1;
}
else if (setting_mode == 4) {
engine_setting = (engine_setting + 7) % 9 + 1;
}
}
else if (save_state == LOW && prev_save_state == HIGH) {
// save the current setting value and switch to the next setting mode
setting_mode = (setting_mode + 1) % 5;
}
}
prev_up_state = up_state;
prev_down_state = down_state;
prev_save_state = save_state;
prev_setting_state = setting_state;
}
void loop() {
hum = dht.readHumidity();
temp = dht.readTemperature();
DateTime now = RTC.now();
if (isnan(temp) || isnan(hum)) {
// Print an error message
lcd.setCursor(0, 0);
lcd.print("No Sensor Detect");
}
else {
dtostrf(temp, 4, 1, tempStr);
dtostrf(hum, 2, 0, humStr);
}
check_buttons();
// display the current setting mode and value
if (setting_mode == Temperature) {
lcd.setCursor(0, 0);
lcd.print("Temp Mode");
lcd.setCursor(0, 1);
lcd.print("T: ");
lcd.print(temp_setting);
lcd.print(" C");
}
else if (setting_mode == Humidity) {
lcd.setCursor(0, 0);
lcd.print("Hum Mode");
lcd.setCursor(0, 1);
lcd.print("H: ");
lcd.print(hum_setting);
lcd.print(" %");
}
else if (setting_mode == Day) {
lcd.setCursor(0, 0);
lcd.print("Day Mode");
lcd.setCursor(0, 1);
lcd.print("D: ");
lcd.print(day_setting);
}
else if (setting_mode == Engine) {
lcd.setCursor(0, 0);
lcd.print("Engine Mode");
lcd.setCursor(0, 1);
lcd.print("M: ");
lcd.print(engine_setting);
}
else if (setting_mode == Normal)
{
// display the normal mode screen
lcd.clear();
// set temp
lcd.setCursor(0, 0);
lcd.write(byte(0));
lcd.print(tempStr);
lcd.setCursor(5, 0);
lcd.write(byte(2));
lcd.print("C");
// set Humidity
lcd.setCursor(8, 0);
lcd.write(byte(1));
lcd.print(humStr);
lcd.print("%");
//Motor Time
lcd.setCursor(13, 0);
lcd.print("M");
lcd.print(":");
lcd.print(engine_setting);
// day and counter
lcd.setCursor(0, 1);
// get the current date and time
DateTime current = RTC.now();
// get the start date and time
DateTime start = DateTime(start_time / 1000);
// get the difference between current and start
TimeSpan diff = current - start;
// calculate the number of days passed
day_count = diff.days();
// display the number of days passed
lcd.print(day_count);
lcd.print(" = ");
// display the remaining days
lcd.print("D ");
lcd.print(day_setting - day_count);
}
// control the relay and the fan based on the temperature and humidity settings
if (temp > temp_setting) {
// turn on the relay and the fan
digitalWrite(RELAY_PIN, HIGH);
digitalWrite(FAN_PIN, HIGH);
}
else if (temp < temp_setting - 1) {
// turn off the relay and the fan
digitalWrite(RELAY_PIN, LOW);
digitalWrite(FAN_PIN, LOW);
}
// control the LEDs based on the engine time and the days
if (millis() - engine_time >= engine_interval * engine_setting) {
// turn on the first LED and run the engine for one minute
digitalWrite(LED1_PIN, HIGH);
// add your code to run the engine here
delay(engine_duration);
// turn off the first LED and stop the engine
digitalWrite(LED1_PIN, LOW);
// add your code to stop the engine here
// update the engine time
engine_time = millis();
}
if (day_count >= day_setting) {
// turn on the second LED and indicate the end of the program
digitalWrite(LED2_PIN, HIGH);
// add your code to end the program here
}
else if (day_count >= day_setting - 1) {
// turn on the third LED and indicate the last day
digitalWrite(LED3_PIN, HIGH);
// add your code to do something on the last day here
}
delay(300);
}
