LCD Updating Information with Serial Communication

Projects Programming
1

Hello, this is my first time posting and as well as working with Arduino LCD Display.
I am trying to create this status update screen, where if serial communication is established the screen will read "ONLINE" and if its not then "OFFLINE".

void systemconnection(boolean online){
    int maxStringLength = 158; //String Pixel Width
    int maxStringWidth = 8; //String Pixel Height
    tft.fillRect(50, 50, maxStringLength, maxStringWidth,ILI9341_BLACK); //draw over previous status update
    tft.setCursor(50,50);

    if (online){
      //status online
      tft.setTextColor(ILI9341_WHITE);
      tft.print("CONNECTION: ");

      tft.setTextColor(ILI9341_GREEN);
      tft.print("ONLINE");
    }
    else if (!online){
      //status online
      tft.setTextColor(ILI9341_WHITE);
      tft.print("CONNECTION: ");

      tft.setTextColor(ILI9341_RED);
      tft.print("OFFLINE");

    }

}

tft.fillRect(50, 50, maxStringLength, maxStringWidth,ILI9341_BLACK); //draw over previous

The problem here is that when communication is restablished or disconnected the print statements overwrite each other, I call this function here,

void gloveInterface() {
  // Set Strings
  int receivedData[5];

  tft.fillScreen(ILI9341_BLACK);
  String thumb = "Thumb: ";
  String index = "Index: ";
  String middle = "Middle: ";
  String ring = "Ring: ";
  String pinky = "Pinky: ";
  
  while (true) {  
    if (Serial.available()) {
      //Read the received data
      Serial.readBytes((byte*)receivedData, sizeof(receivedData));
      // SYSTEM ONLINE
      systemconnection(true);
      
      // Clear region for updated data
      tft.fillRect(195, centerTextHeight(-40) - 10, 60, 20, ILI9341_BLACK);
      tft.fillRect(195, centerTextHeight(-20) - 10, 60, 20, ILI9341_BLACK);
      tft.fillRect(195, centerTextHeight(0) - 10, 60, 20, ILI9341_BLACK);
      tft.fillRect(195, centerTextHeight(20) - 10, 60, 20, ILI9341_BLACK);
      tft.fillRect(195, centerTextHeight(40) - 10, 60, 30, ILI9341_BLACK);

      // Thumb
      tft.setTextColor(ILI9341_WHITE);
      tft.setCursor(centerTextWidth(thumb, 12), centerTextHeight(40));
      tft.println(thumb + String(receivedData[0]/256));

      // Index
      tft.setTextColor(ILI9341_WHITE);
      tft.setCursor(centerTextWidth(index, 12), centerTextHeight(-40));
      tft.println(index + String(receivedData[1]/256));

      // Middle
      tft.setTextColor(ILI9341_WHITE);
      tft.setCursor(centerTextWidth(middle, 12), centerTextHeight(-20));
      tft.println(middle + String(receivedData[2]/256));

      // Ring
      tft.setTextColor(ILI9341_WHITE);
      tft.setCursor(centerTextWidth(ring, 12), centerTextHeight(0));
      tft.println(ring + String(receivedData[3]/256));

      // Pinky
      tft.setTextColor(ILI9341_WHITE);
      tft.setCursor(centerTextWidth(pinky, 12), centerTextHeight(20));
      tft.println(pinky + String(receivedData[4]/256));
    }else{
        systemconnection(false);
    }
  }
}

In this line I am trying to overwrite what was previously on display but would the lcd.clear() function work better. Is there better way I can update information without the previous message interfereing.

2

Try overwriting the old data with old data in background color, then write new data in foreground color.

3

Added this chunk of code:

void systemconnection(boolean online){
    int maxStringLength = 158; //String Pixel Width
    int maxStringWidth = 8; //String Pixel Height
    //tft.fillRect(50, 50, maxStringLength, maxStringWidth,ILI9341_BLACK); //draw over previous status update
    tft.setCursor(50,50);

    if (online){
      //status online
      tft.setTextColor(ILI9341_BLACK);
      tft.print("CONNECTION: OFFLINE");
      tft.setCursor(50,50);

      tft.setTextColor(ILI9341_WHITE);
      tft.print("CONNECTION: ");

      tft.setTextColor(ILI9341_GREEN);
      tft.print("ONLINE");
    }
    else if (!online){
      //status online
    
      tft.setTextColor(ILI9341_BLACK);
      tft.print("CONNECTION: ONLINE");
       tft.setCursor(50,50);
      ///////////////////////////////////////////
     
      tft.setTextColor(ILI9341_WHITE);
      tft.print("CONNECTION: ");

      tft.setTextColor(ILI9341_RED);
      tft.print("OFFLINE");

    }

}

once I lose connection, unplug either the tx/rx pin it works fine but when the connection is reestablished the two print statements overlap and the screen flashes between both.

4

In "online" set a flag to say "we've already written this, don't write it again" something like:

if (online) {
  if (!been_here) { // if we have not written the tft text before, then proceed to do it
    been_here = 1; // this says, "don't pass the if() condition in the line above"
    tft.setTextColor...
.
.
  }
}

AND in "!online" clear that flag

else if (!online) {
  been_here = 0; // clear the "online" flag so if that happens, the tft text will be written
  tft.setTextColor...
.
.
}
5

I did something along the lines of that but on boot up there is constant flash between the two still, I am pretty sure the fact that I am using serial.available() is making the message flash between the two, is there a buffer between when data is being sent that I can account for?

6

My guess is the flashing is from the constant over-writing on the tft... maybe caused by "online" and "not online" are occurring very (too) frequently. Try to make the over-writing happen only once (both "online" and "not online") until the other state has occurred. If your online/not online is rapidly changing, the problem is not in tft over-writing.

7

i fixed the problem i created a time buffer between when serial is available so that if check flag is false and the difference between when check flags have changed were less than 1 second then it wouldn't switch. I guess there is a small gap between when the data was being sent so it would switch between the two because there was a 10ms where it wasn't available.

unsigned long offlineTime = 0;

  offlineTime = millis(); //set this at the end of serial.available()
    }
    else{
      if (!stopLoop && (millis() - offlineTime > 300)){ //the conditions
        systemconnection(false);
      }
      
    }
8

Very good!

1 Like
9

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