[Solved] Text flickering on ILI9341 TFT Displays

/*

 Clock-Temp-Humid-TFT-ESP32

 ==========================

 Displays current date and time using ntp sync via internal WI-FI.

 Measures temperature and humidity using DHT22 sensor.

 Data is displayed on KMRTM28028-SPI - 2.8" TFT SPI 240x320.

 Data is also sent to Blynk.

 Also, a LED is added to play with Blynk on smartphone.

 Circuit:

 Humidity & temperature sensor/module DHT22

 1) + --> ESP32 +5V

 2) OUT --> ESP32 26

 3) GND --> ESP32 GND

 2.8' TFT SPI 240*320:

 1) VCC --> ESP32 +3.3V

 2) GND --> ESP32 GND

 3) CS --> ESP32 15

 4) RESET --> ESP32 4

 5) D/C --> ESP32 2

 6) SDI (MOSI) --> ESP32 23

 7) SCK --> ESP32 18

 8) LED --> ESP32 +3.3V

 9) SDO (MISO) --> ESP32 19

 10) T_CLK --> SCK --> ESP32 18

 11) T_CS --> ESP32 21

 12) T_DIN --> SDI (MOSI) --> ESP32 23

 13) T_OUT --> SDO (MISO) --> ESP32 19

 14) T_IRQ --> not connected

 Capacitor:

 ESP32 CN --> Capacitor --> GND // No need to press Boot button to upload sketch

 LED:

 ESP32 13 --> 1kΩ resistor --> GND // For fun. Turn LED on/off with Blynk app on smartphone

 Created: 2021-01-11 by Zoltar358.

 Modified: 2021-01-22 by Zoltar358.

 Compiled and tested with VS-Code (PlatformIO) on ESP32-WROOM-32D.

  https://www.aliexpress.com/item/4001050278803.html  // Or just search for ESP32-WROOM-32D

 Special thanks to XTronical for his video

 on how to wire up ILI9341 TFT LCD to ESP32.

 Give him some love and subscribe to his YouTube channel.

  https://www.xtronical.com 

  https://youtu.be/rq5yPJbX_uk 

*/

#include "Arduino.h" // Required by PlatformIO

#include "WiFi.h" // WiFi library

#include <WiFiClient.h> // WiFi Client library

#include <BlynkSimpleEsp32.h> // Blynk library

#include "Time.h" // Time library

#include "Wire.h" // Wire library

#include "DHTesp.h" // DHT Temperature and Humidity Sensor

#include "SoftwareSerial.h" // Serial library

#include "TFT_eSPI.h" // Hardware-specific library for TFT display

#include "auth.h" // Credentials (in seperate auth.h file)

 // const char *ssid = "SSID";

 // const char *password = "PASSWORD";

 // char auth[] = "BLYNK_AUTH_TOKEN";

 // const char *ntpServer = "pool.ntp.org";

DHTesp dht; // Invoke DHTesp

 // Define fonts

#define FF21 FreeSansBold9pt7b // Free Sans Bold 9pt

#define FF22 FreeSansBold12pt7b // Free Sans Bold 12pt

#define FF23 FreeSansBold18pt7b // Free Sans Bold 18pt

#define FF24 FreeSansBold24pt7b // Free Sans Bold 24pt

#define TFT_DARKNAVY 0x0004 // Backround color

TFT_eSPI tft = TFT_eSPI(); // Invoke TFT library

TFT_eSprite spr = TFT_eSprite(&tft); // Invoke Sprite class

const long gmtOffset_sec = 3600; // Offset for Europe/Warsaw (GMT+1)

const int daylightOffset_sec = 3600; // Daylight offset for Europe/Warsaw (GMT+1)

unsigned long targetTime = 0;

void plotCalendar() // Function to draw calendar data

{

 struct tm timeinfo;

 if (!getLocalTime(&timeinfo)) // Check if time is set

 {

 String errorMessage = "Failed to obtain time"; // Error message to variable

 tft.setTextColor(TFT_YELLOW, TFT_DARKNAVY); // Set text color and background

 tft.setFreeFont(&FF21); // Set font

 tft.drawString(errorMessage, 115, 8); // Print error message

 return; // Return to main

 }

 char weekDay[9]; // Define char for weekDay value

 char fullYear[11]; // Define char for fullYear value

 char fullTime[9]; // Define char for fullTime value

 strftime(weekDay, 9, "%A", &timeinfo); //

 strftime(fullYear, 11, "%F", &timeinfo); // Configure display formats

 strftime(fullTime, 9, " %R ", &timeinfo); //

 spr.setTextColor(TFT_GREEN, TFT_DARKNAVY); // Set text color and background

 spr.setFreeFont(&FF23); // Set font

 spr.drawString(weekDay, 115, 6); // Print weekDay

 spr.setTextColor(TFT_LIGHTGREY, TFT_DARKNAVY); // Set text color and background

 spr.setFreeFont(&FF22); // Set font

 spr.drawString(fullYear, 115, 40); // Print fullYear

 spr.setTextColor(TFT_ORANGE, TFT_DARKNAVY); // Set text color and background

 spr.setFreeFont(&FF23); // Set font

 spr.drawString(fullTime, 115, 67); // Print fullTime

}

void plotTemperature() // Function to draw temperature data

{

 float temperature = dht.getTemperature(); // Get temperature value from sensor

 Blynk.virtualWrite(V5, temperature); // Send temperature value to Blynk virtual pin V5

 String celcius = " C"; // Define Celsius unit

 String fahrenheit = " F"; // Define Fahrenheit unit

 String kelvin = " K"; // Define Kelvin unit

 spr.setFreeFont(&FF22); // Set font

 spr.setTextColor(TFT_GREEN, TFT_DARKNAVY); // Set text color and background

 spr.drawString("TEMPERATURE", 115, 7, 4); // Print title

 spr.setTextColor(TFT_ORANGE, TFT_DARKNAVY); // Set text color and background

 char bufT[6]; // Define char for Celcius temperature value

 dtostrf(temperature, 2, 1, bufT); // Convert Celsius temperature value to string

 strcat(bufT, celcius.c_str()); // Add Celsius sign to temperature value

 spr.setFreeFont(&FF23); // Set font

 spr.drawString(bufT, 115, 35); // Print temperature value

 float temperatureF = dht.toFahrenheit(temperature); // Convert Celsius to Fahrenheit

 spr.setTextColor(TFT_DARKGREY, TFT_DARKNAVY); // Set text color and background

 char bufTF[7]; // Define char for Fahrenheit temperature value

 dtostrf(temperatureF, 2, 2, bufTF); // Convert Fahrenheit temperature value to string

 strcat(bufTF, fahrenheit.c_str()); // Add Fahrenheit sign to temperature value

 spr.setFreeFont(&FF22); // Set font

 spr.drawString(bufTF, 56, 71); // Print Fahrenheit temperature value

 float temperatureK = temperature + 273.15; // Convert Celsius to Kelvin

 spr.setTextColor(TFT_DARKGREY, TFT_DARKNAVY); // Set text color and background

 char bufTK[7]; // Define char for Kelvin temperature value

 dtostrf(temperatureK, 2, 2, bufTK); // Convert Kelvin temperature value to string

 strcat(bufTK, kelvin.c_str()); // Add Kelvin sign to temperature value

 spr.setFreeFont(&FF22); // Set font

 spr.drawString(bufTK, 170, 71); // Print Kelvin temperature value

}

void plotHumidity() // Function to draw humidity data in desired position

{

 float humidity = dht.getHumidity(); // Get humidity value from sensor

 Blynk.virtualWrite(V6, humidity); // Send humidity value to Blynk virtual pin V6

 String percent = "%"; // Define percent sign (%)

 spr.setFreeFont(&FF22); // Set font

 spr.setTextColor(TFT_GREEN, TFT_DARKNAVY); // Set text color and background

 spr.drawString("HUMIDITY", 115, 20, 4); // Print title

 char bufH[5]; // Define char for humidity value

 dtostrf(humidity, 2, 1, bufH); // Convert humidity value to string

 strcat(bufH, percent.c_str()); // Add percent sign to humidity value

 spr.setFreeFont(&FF23); // Set font

 spr.setTextColor(TFT_ORANGE, TFT_DARKNAVY); // Set text color and background

 // spr.setTextPadding(120); // Set text padding to avoid overlapping

 spr.drawString(bufH, 115, 50); // Print humidity value

}

void setup() // Setup (runs only once)

{

 Serial.begin(115200); // Initialize serial port

 Blynk.begin(auth, ssid, password); // Connect to Blynk

 tft.init(); // Initialize TFT display

 tft.setRotation(2); // Set rotation to portrait

 tft.fillScreen(TFT_RED); // Fill screen red

 tft.fillRect(0, 122, 239, 3, TFT_RED); // Draw red horizontal line

 tft.fillRect(0, 245, 239, 3, TFT_RED); // Draw red horizontal line

 spr.setTextDatum(1); // Set text alignment: center

 dht.setup(26, DHTesp::DHT22); // Connect DHT sensor to GPIO 26

 Serial.printf("Connecting to %s ", ssid); // Print connection message on serial monitor

 WiFi.begin(ssid, password); // Connect to WiFi

 while (WiFi.status() != WL_CONNECTED) // Check if connection is established

 {

 delay(500); // Set delay to 0.5s

 Serial.print("."); // Print dots on serial monitor until connection is established

 }

 Serial.println(); // Print empty line on serial monitor

 Serial.println("Connected to Wi-Fi"); // Inform about established connection on serial monitor

 configTime(gmtOffset_sec, daylightOffset_sec, ntpServer); // Initialize and get the time

 targetTime = millis() + 1000;

 //WiFi.disconnect(true); // Disconnect from WiFi

 //WiFi.mode(WIFI_OFF); // Switch WiFi module off

}

void loop() // Loop (runs continuosly)

{

 Blynk.run(); // Run Blynk applet

 delay(dht.getMinimumSamplingPeriod()); // Delay before getting sensor data

 if (targetTime < millis()) {

 targetTime = millis() + 100;//10000;

 spr.createSprite(230, 100); // Create sprite

 spr.fillSprite(TFT_DARKNAVY); // Fill sprite area with (TFT_DARKNAVY)

 plotCalendar(); // Draw calendar section

 spr.pushSprite(5, 5); // Push sprite to its position

 spr.createSprite(230, 100); // Create sprite

 spr.fillSprite(TFT_DARKNAVY); // Fill sprite area with (TFT_DARKNAVY)

 plotTemperature(); // Draw temperature section

 spr.pushSprite(5, 110); // Push sprite to its position

 spr.createSprite(230, 100); // Create sprite

 spr.fillSprite(TFT_DARKNAVY); // Fill sprite area with (TFT_DARKNAVY)

 plotHumidity(); // Draw humidity section

 spr.pushSprite(5, 215); // Push sprite to its position

 }

}

// #################################### EOF ####################################