LCD flickering with ethernet

Projects Programming
5

Example loop() to show separating the update of the LCD, not using clear() and millis() timing to get rid of delay and do "multitasking". Illustration, not tested.

void loop ()
{
   doEthernet();
   updateLCD();
}

void doEthernet()  // called very time through loop, but executes only every 3 seconds.
{
   static unsigned long timer = 0;
   unsigned long interval = 3000;
   if (millis() - timer >= interval)
   {
      timer = millis();
      float inputReading = distanceSensor.measureDistanceCm();
      int CurPercentage = (100 - (inputReading / MaxHeight * 100));
      int CurVol = MaxVol / 100 * CurPercentage;

      // update Progress Bar
      updateProgressBar(CurPercentage, 100, 1);

      // Wait for an incoming connection
      EthernetClient client = server.available();
      if (!client)
         return;
      Serial.println(F("New client"));

      while (client.available()) client.read();
      StaticJsonDocument<100> doc;
      doc["data"] = CurPercentage;

      // Write response headers
      client.println(F("HTTP/1.0 200 OK"));
      client.println(F("Content-Type: application/json"));
      client.println(F("Connection: close"));
      client.print(F("Content-Length: "));
      client.println(measureJsonPretty(doc));
      client.println();
      serializeJsonPretty(doc, client);
      client.stop();
   }
}

void updateLCD()  // called very time through loop, but executes only every 1 second.
{
   static unsigned long timer = 0;
   // I know that there is no use updating the LCD faster than the ethernet
   // just showing that you can
   unsigned long interval = 1000;
   if (millis() - timer >= interval)
   {
      timer = millis();
      lcd.setCursor(0, 0);
      lcd.print("                "); // overwrite old data with spaces
      lcd.setCursor(1, 0); // reset cursor
      lcd.print(CurVol);
      lcd.print(" L - ");
      lcd.print(CurPercentage);
      lcd.print(" %");
   }
}