LCD backlight on/off

Using Arduino Programming Questions
1

I have an RTC clock built with an ESP32 and a 16x2 LCD connected with an I2C backpack attached. I'm trying to get my backlight to turn off and on at specific times. nothing I do in void loop() does anything but if I change lcd.backlight() to lcd.noBacklight() in the void setup() it will turn the backlight off.

I'm using the <hd44780ioclass/hd44780_I2Cexp.h>
library.

other than the backlight problem I'm currently trying to figure out everything works well and have no other issues. below is my code (ssid and password have been changed)

#include <Wire.h>
#include <WiFi.h>
#include <NTPClient.h>               
#include <TimeLib.h>                 
#include <hd44780.h>    
#include <hd44780ioclass/hd44780_I2Cexp.h>
hd44780_I2Cexp lcd(0x27, 16, 2);

const char *ssid     = "NETWORK_NAME";    /*Replace with your network SSID*/
const char *password = "network_password";  /*Replace with network password*/
WiFiUDP ntpUDP;
NTPClient timeClient(ntpUDP, "time.nist.gov", -21600, 60000);
char Time[ ] = "TIME:00:00:00";
char Date[ ] = "DATE:00/00/2000";
byte last_second, second_, minute_, hour_, month_, day_;
int year_;
unsigned long turnOffTime, turnOntime;

void setup(){
  Serial.begin(115200);
  lcd.init(); /*Initialize LCD display*/
  lcd.backlight();  /*ON LCD Backlight*/
  lcd.setCursor(0, 0);  /*Set cursor*/
  lcd.print("Time");  /*print time on LCD*/
  lcd.setCursor(0, 1);  /*Set LCD cursor*/
  lcd.print(Date);  /*Print date*/
  WiFi.begin(ssid, password);  /*begin WiFi*/
  Serial.print("Connecting.");
  while ( WiFi.status() != WL_CONNECTED ) {
    delay(500);
    Serial.print(".");
  }

  Serial.println("connected");
  timeClient.begin();
  delay(1000);
  lcd.clear();  /*clear LCD display*/
}

void loop(){
  timeClient.update();
  unsigned long unix_epoch = timeClient.getEpochTime();    // Get Unix epoch time from the NTP server
    const int turnOffTime = 2100;
    const int turnOnTime = 800;

   second_ = second(unix_epoch);
  if (last_second != second_) {
    minute_ = minute(unix_epoch);
    hour_   = hour(unix_epoch);
    day_    = day(unix_epoch);
    month_  = month(unix_epoch);
    year_   = year(unix_epoch);
    Time[12] = second_ % 10 + 48;
    Time[11] = second_ / 10 + 48;
    Time[9]  = minute_ % 10 + 48;
    Time[8]  = minute_ / 10 + 48;
    Time[6]  = hour_   % 10 + 48;
    Time[5]  = hour_   / 10 + 48;
    Date[5]  = month_   / 10 + 48;
    Date[6]  = month_   % 10 + 48;
    Date[8]  = day_  / 10 + 48;
    Date[9]  = day_  % 10 + 48;
    Date[13] = (year_   / 10) % 10 + 48;
    Date[14] = year_   % 10 % 10 + 48;
    Serial.println(Time);  /*Prints time on serial monitor*/
    Serial.println(Date);  /*Print date on serial monitor*/

   if (hour() >= turnOffTime && hour() < turnOnTime) { lcd.noBacklight();
  }
  else 
  { lcd.backlight();

 lcd.setCursor(0, 0);  /*Set LCD cursor*/
    lcd.print(Time);  /*display time on LCD*/
    lcd.setCursor(0, 1); /*Set LCD cursor*/
    lcd.print(Date);  /*Display date on LCD*/
    last_second = second_;

    
  }
  delay(200);
}
}
2

Hello zimtech

Welcome to the worldbest Arduino forum ever.

I assume that you have written the programme by yourself, then it is quite easy to find the error.

There's a trick to figuring out why something isn't working:

Use a logic analyzer to see what happens.
Put Serial.print statements at various places in the code to see the values of variables, especially ones that control the LCD, and determine whether they meet your expectations.

Have a nice day and enjoy coding in C++.

3

Did you ever think that the value of hour() would be this big?

1 Like
4

I got it to work, but I'm not sure what you're asking? The clock is set in a 24 hour format not 12. I used better if statements to make it work right.

if (Time) {
(turnOfflight[15]);
lcd.noBacklight();
} if (Time) {
(turnOnlight[16]);
lcd.backlight();
}
5

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