5" TFT Display and Module RA8875

Nice update on your design challenge project.  Good work on getting everything connected and running.  That was some first class detective work there.

Gene

Hi Gene, Are you familiar with Arduino code? I am having an issue with this project (I picked it back up again using an Arduino Mega 2560 connected to an RA8875 (with 5 inch touch screen) and also the VS1053 audio player with SD slot).

When I touch the screen, the VS1053 plays the audio file twice as if I pressed it twice.

I think the touch screen connected to the RA8875 is registering when I press the screen and also when I let my finger up.

I don't know how to stop that from happening. From what I am reading on the web, I think it could be a possible debounce issue but I am not sure nor am I familiar enough with Arduino code.

I checked many places on the web to see how I can get this to work but I do not understand software debounce in regards to my specific code.

Any assistance is appreciated. 

Hi Andrew

Not sure if the code i placed above shows what you are looking for. I agree with you that it has to be on a release but what if someone presses one touch screen button then slides their finger to another image and let go there?

how is that accounted for with your code?

Regards

Rob

I'm not taking account, per-se, of touch down, move release.  When I ask for status (line 05), the response will be -1 if no touch detected, or another value that equates to TOUCH_PRESSED, TOUCH_MOVED, TOUCH_RELEASED.  Whilst I don't directly action on the TOUCH_MOVE status, when I get the TOUCH_PRESSED I capture the widget index that was touched (line 08).  When the status is TOUCH_RELEASED, I compare the widget index that was reported at that point with the one at the time of touch and if they are the same then I know that the person touched down and released on the same widget (line 16.)

I looked at the code before to determine that it works on a touch point (co-ordinate) rather than reporting 'what' was touched.  So you will need to do this comparison yourself.  Relevant code appear to be:

void waitForTouchEvent(tsPoint_t * point) {
  /* Clear the touch data object and placeholder variables */
  memset(point, 0, sizeof(tsPoint_t));

  /* Clear any previous interrupts to avoid false buffered reads */
  uint16_t x, y;
  tft.touchRead(&x, &y);
  delay(1);


  /* Wait around for a new touch event (INT pin goes low) */
  while (digitalRead(RA8875_INT)) {
  }

  /* Make sure this is really a touch event */
  if (tft.touched()) {
    tft.touchRead(&x, &y);
    point->x = x;
    point->y = y;
    Serial.print("Touch: ");
    Serial.print(point->x); Serial.print(", "); Serial.println(point->y);
  }  else {
    point->x = 0;
    point->y = 0;
  }
}

Line 12 is waiting for a touch and looping until it detects one - digitalRead(RA8875_INT) becomes 0.  This sets an interrupt flag on the controller. 

Line 16 then tests to see if the screen was touched (returns true if the interrupt flag is set) and if it was, gets the co-ordinates into variables X and Y ( line 17) - reading the co-ordinates clears the flag.  So these three bits of code give you the code for detecting a touch and where.  I suspect you may be right with this controller: the code may run fast enough that it detects a touch, reports it and reads it, before the finger is removed and then it reports a touch again.  To debounce it you will want to 'wait' to process a touch for a small amount of time.

Using the above as an example - you should be able to adjust for your own use:

unsigned long lastTouchTime = millis();

void waitForTouchEvent(tsPoint_t * point) {
  /* Clear the touch data object and placeholder variables */
  memset(point, 0, sizeof(tsPoint_t));

  /* Clear any previous interrupts to avoid false buffered reads */
  uint16_t x, y;
  tft.touchRead(&x, &y);
  delay(1);


  /* Wait around for a new touch event (INT pin goes low) */
  while (digitalRead(RA8875_INT)) {
  }

  /* Make sure this is really a touch event */
  if (tft.touched()) {
    tft.touchRead(&x, &y);
    if(millis() - lastTouchTime > 500) {     // if 500mS have passed since last processing a touch then process it.
         point->x = x;
         point->y = y;
         Serial.print("Touch: ");
         Serial.print(point->x); Serial.print(", "); Serial.println(point->y);
    } else {
          // ignore the press as it happened too quickly
          // This else clause is only needed if you need to do something when ignoring the press.
    }
    lastTouchTime = millis();
  } else {
    point->x = 0;
    point->y = 0;
  }
}

I added line 01 to declare a global variable to keep track of the time the screen was touched.  I added line 20 and 25-28 to wrap around the code to process the touch and if less than 500mS has passed, it ignores it. Line 29 then sets the time it was last touched. You can play around with this value and make it as small as possible - for example, I used a value of 150mS to debounce a mechanical rotary encoder pushswitch. 

You must still execute the tft.touchRead(&x, &y) (line 19) because it is responsible for clearing the flag.

So, this should work by:

1. waiting for a touch event (line 14)
2. detect if it was a real touch (is the touch flag set?) - line 18
3. read the co-ordinates and reset the flag - line 19
4. check that at least 500mS has passed since last processing a touch - line 20
5. capture the time of the last press - line 29

I can't test this of course but it looks ok.  Line 14 you will need to work out for your own application: in the code above it loops forever waiting for a touch - if this isn't something you want, then you'll need to adjust.  The three bits of code I pointed out are the ones you need to work with.

Thank you Andrew, I will try this code when i get off of work.

I was thinking that the Interrupt pin (18) was the key and i was even going try the hardware way of putting a capacitor in line if i couldn't figure out the code.

Thank you again for letting me try this code and I will let you know the outcome!

Regards,

Hello Andrew,

i just tried the code (just got some time to try it) and it did not work.

I noticed that if i hold my finger on the screen, it continue to speak to me saying the same thing as if i keep pressing it.

very interesting dilemma.

I don't have one of these to test unfortunately.  A bit of googling indicates that the interrupt pin goes HIGH when the panel is being touched, so the while() loop on line 14 isn't quite right I don't think.  Can you cut your code down to the absolute simplest version you can, just to get a grip on the touch handling - in fact, start a new sketch that just does screen touch detect, outputting the X,Y co-ordinates to the Serial monitor every time it detects a touch.  What we should be aiming for, in pseudocode, is something like:

loop()

     clear touch data and reset read interrupts

     while(not touched)  <-- interrupt pin is LOW

          do nothing

     while(touched) <-- interrupt pin is HIGH

          save X,Y coordinates

     if touched and time since last touch > 500mS

          print X,Y coordinates

          save last touch time

     end if

end loop

What this should do is wait until it detects a touch, then stores the X,Y coordinates until it no longer detects a touch, then prints out the co-ordinates if enough time has passed.

For the moment, forget playing your audio file. startup() should do the minimum it needs to initialise the serial monitor and the display, and loop() should do the above code.  See what happens: are you getting multiple output to the Serial monitor every time you press?  You could try it without the time elapsed element first if you want - it may be clever enough to already detect 'bounce', or indeed not bounce at all.  If we can get this working, then you can expand on it incrementally to detect movement whilst touching (X,Y changes as it detects touches) and so on.

Can I ask - how much coding experience do you have? 

I don't have one of these to test unfortunately.  A bit of googling indicates that the interrupt pin goes HIGH when the panel is being touched, so the while() loop on line 14 isn't quite right I don't think.  Can you cut your code down to the absolute simplest version you can, just to get a grip on the touch handling - in fact, start a new sketch that just does screen touch detect, outputting the X,Y co-ordinates to the Serial monitor every time it detects a touch.  What we should be aiming for, in pseudocode, is something like:

loop()

     clear touch data and reset read interrupts

     while(not touched)  <-- interrupt pin is LOW

          do nothing

     while(touched) <-- interrupt pin is HIGH

          save X,Y coordinates

     if touched and time since last touch > 500mS

          print X,Y coordinates

          save last touch time

     end if

end loop

What this should do is wait until it detects a touch, then stores the X,Y coordinates until it no longer detects a touch, then prints out the co-ordinates if enough time has passed.

For the moment, forget playing your audio file. startup() should do the minimum it needs to initialise the serial monitor and the display, and loop() should do the above code.  See what happens: are you getting multiple output to the Serial monitor every time you press?  You could try it without the time elapsed element first if you want - it may be clever enough to already detect 'bounce', or indeed not bounce at all.  If we can get this working, then you can expand on it incrementally to detect movement whilst touching (X,Y changes as it detects touches) and so on.

Can I ask - how much coding experience do you have?