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 Rob,

does it have a library you use to detect touches, positions etc?  I have a similar situation with a different touch screen.  The library I use (Picaso processor) will event a touchdown and a touch up.  So you could, for example, change a graphic on touch down and action the command on touch up: in my code on touchdown I register what was pressed, and on touch up I check it’s the same widget before executing the action.  That way, if someone presses down on a widget, slides their finger off it and then releases, I can tell and not action the command (in other words, the user can ‘abort’ their action.) 

What I found is that it could register multiple touches at the touch point because of the speed of execution of code.  So, as an example, when I pressed the ‘cancel’ button to close a dialog, the code would close that dialog but my finger was still touching the screen (because nano-second execution speed) and it would then event a touch on the widget that was on the screen at that point.  Hope that makes sense....

Anyway, it wasn’t debouncing as such - like a mechanical button - but just you can’t physically move fast enough.  I put a very small delay in to ignore touches once one was detected - I’m not in front of the code, but I played around with the timing to get it right and 500mS worked ok believe it or not.  Also, as I noted above, I wrote the code to only action on the touch up (release) that way multiple touch down events on a widget wouldn’t cause anything to happen.  If you find that it is registered multiple touch up events on the same widget you could put a check in for that.

It won’t be the same library of course, but I’ll try and post the code I use here later.  It may give you some ideas.

Hi Rob,

does it have a library you use to detect touches, positions etc?  I have a similar situation with a different touch screen.  The library I use (Picaso processor) will event a touchdown and a touch up.  So you could, for example, change a graphic on touch down and action the command on touch up: in my code on touchdown I register what was pressed, and on touch up I check it’s the same widget before executing the action.  That way, if someone presses down on a widget, slides their finger off it and then releases, I can tell and not action the command (in other words, the user can ‘abort’ their action.) 

What I found is that it could register multiple touches at the touch point because of the speed of execution of code.  So, as an example, when I pressed the ‘cancel’ button to close a dialog, the code would close that dialog but my finger was still touching the screen (because nano-second execution speed) and it would then event a touch on the widget that was on the screen at that point.  Hope that makes sense....

Anyway, it wasn’t debouncing as such - like a mechanical button - but just you can’t physically move fast enough.  I put a very small delay in to ignore touches once one was detected - I’m not in front of the code, but I played around with the timing to get it right and 500mS worked ok believe it or not.  Also, as I noted above, I wrote the code to only action on the touch up (release) that way multiple touch down events on a widget wouldn’t cause anything to happen.  If you find that it is registered multiple touch up events on the same widget you could put a check in for that.

It won’t be the same library of course, but I’ll try and post the code I use here later.  It may give you some ideas.

Here's some code I use.  This function, handleTouches(), is called from within loop() but it could be called from wherever needed.  Above, I said I put a delay in - and I did at one point - but I was able to take it out because that actually wasn't the problem I was experiencing (I remember now.)  Because it is called from loop() it may be called hundreds if not thousands of times a second, so the TOUCH events may be checked multiple times but it doesn't matter because I only process on TOUCH RELEASE.

void handleTouches() {
  uint8_t status;
  int8_t imagePressed;

  status = Display.touch_Get(TOUCH_STATUS); // get touchscreen status

  if(status == TOUCH_PRESSED) {
    imagePressed = Display.img_Touched(hndl, -1);
    if (imagePressed != -1) {
      lastImagePressed = imagePressed;
    }
  }

  if(status == TOUCH_RELEASED) {
    imagePressed = Display.img_Touched(hndl, -1);
    if (imagePressed == lastImagePressed) {
      lastImagePressed = 255;
      switch(imagePressed) {
        case POWERBUTTON:
          handlePowerButton();
          break;
        case PREFSBUTTON:
          handlePrefsButton();
          break;
        case DEFAULTSBUTTON:
          handleDefaultsButton();
          break;
        case CANCELBUTTON:
          handleCancelButton();
          break;
….[other case checks]
        default:
          break;
      }
    }
  }
}

This is based on using a library created for the Picaso graphics processor.  I'd have to assume you have access to a similar library although it's likely to work differently.  The principles for processing should be similar though.

Line 05: here, I get hold of the touch status, which can be -1 (no touch) or TOUCH_PRESSED, TOUCH_RELEASED, TOUCH_MOVED.  These are pretty self-explanatory; touch_moved is a detection of touch_pressed and a move of the pointer without an intervening touch_released event.  I'm not interested in this event so I don't process it.

Line 07: if TOUCH_PRESSED status was indicated, then I can ask for which image (widget - button, string, image etc) was touched and remember it.  Note that a touch could be detected not on a widget.  If your library only returns a position (X,Y coordinates) you would need to calculate what was being touched - the library I use does that for me.

Line 14: If TOUCH_RELEASED status was indicated, then I check that the touch occurred on the same widget and only process it if that was the case.  In other words, the user has to touch down and release on the same widget (see the check on line 16.)  You can see this in most UIs: press and release must occur on the same widget and if you change your mind, you can drag off before releasing.  Keyboards, at least physical ones, work differently in that the button registers on touch down rather than touch release. 

ImagePressed is just a 0 (zero) to N index of widgets on the screen which is why I can process them through a Switch construct. 

If I had to summarise:

• Only process on a TOUCH PRESS or a TOUCH RELEASE.
• If the library only reports a co-ordinate, you will need a routine to convert that co-ordinate to a widget.  The widget will cover an area so you would be looking at detecting the co-ordinate in an X,X1, Y,Y1 range.  Looking at the touch calibration example for this driver in Adafruit's GitHub, it looks like it is co-ordinate based.
• When you detect a TOUCH PRESS, save the 'widget' pressed and ignore any more TOUCH PRESS events until you get a TOUCH RELEASE.
• Ensure that the TOUCH RELEASE occurs on the same widget as the TOUCH PRESS you registered.
• If the library doesn't flag anything except a touch point, your approach would be to do something like:
  • Detect a touch point
  • Save initial coordinates and convert to 'screen widget touched'
  • while (touch detected), save last coordinates and convert to screen widget touched // this loops until no touch detected
  • Does initial screen widget touched == last screen widget touched?  If yes, process the touch, otherwise, the touch point was moved so do nothing. [REMEMBER: that the widget covers an area so it isn't a SPECIFIC point you want to compare but a determined widget] 

Hope this gives you some pointers.

Hi Andrew,

The RA8875 library does have a program that detects touches as a calibration test. Here it is:

#include <SPI.h>

#include "Adafruit_GFX.h"

#include "Adafruit_RA8875.h"

#define RA8875_INT     3

#define RA8875_CS      10

#define RA8875_RESET   9

Adafruit_RA8875 tft = Adafruit_RA8875(RA8875_CS, RA8875_RESET);

tsPoint_t       _tsLCDPoints[3];

tsPoint_t       _tsTSPoints[3];

tsMatrix_t      _tsMatrix;

/**************************************************************************/

/*!

    @brief Calculates the difference between the touch screen and the

           actual screen co-ordinates, taking into account misalignment

           and any physical offset of the touch screen.

    @note  This is based on the public domain touch screen calibration code

           written by Carlos E. Vidales (copyright (c) 2001).

           For more information, see the following app notes:

           - AN2173 - Touch Screen Control and Calibration

             Svyatoslav Paliy, Cypress Microsystems

           - Calibration in touch-screen systems

             Wendy Fang and Tony Chang,

             Analog Applications Journal, 3Q 2007 (Texas Instruments)

*/

/**************************************************************************/

int setCalibrationMatrix( tsPoint_t * displayPtr, tsPoint_t * screenPtr, tsMatrix_t * matrixPtr)

{

  int  retValue = 0;

  matrixPtr->Divider = ((screenPtr[0].x - screenPtr[2].x) * (screenPtr[1].y - screenPtr[2].y)) -

                       ((screenPtr[1].x - screenPtr[2].x) * (screenPtr[0].y - screenPtr[2].y)) ;

  if( matrixPtr->Divider == 0 )

  {

    retValue = -1 ;

  }

  else

  {

    matrixPtr->An = ((displayPtr[0].x - displayPtr[2].x) * (screenPtr[1].y - screenPtr[2].y)) -

                    ((displayPtr[1].x - displayPtr[2].x) * (screenPtr[0].y - screenPtr[2].y)) ;

    matrixPtr->Bn = ((screenPtr[0].x - screenPtr[2].x) * (displayPtr[1].x - displayPtr[2].x)) -

                    ((displayPtr[0].x - displayPtr[2].x) * (screenPtr[1].x - screenPtr[2].x)) ;

    matrixPtr->Cn = (screenPtr[2].x * displayPtr[1].x - screenPtr[1].x * displayPtr[2].x) * screenPtr[0].y +

                    (screenPtr[0].x * displayPtr[2].x - screenPtr[2].x * displayPtr[0].x) * screenPtr[1].y +

                    (screenPtr[1].x * displayPtr[0].x - screenPtr[0].x * displayPtr[1].x) * screenPtr[2].y ;

    matrixPtr->Dn = ((displayPtr[0].y - displayPtr[2].y) * (screenPtr[1].y - screenPtr[2].y)) -

                    ((displayPtr[1].y - displayPtr[2].y) * (screenPtr[0].y - screenPtr[2].y)) ;

    matrixPtr->En = ((screenPtr[0].x - screenPtr[2].x) * (displayPtr[1].y - displayPtr[2].y)) -

                    ((displayPtr[0].y - displayPtr[2].y) * (screenPtr[1].x - screenPtr[2].x)) ;

    matrixPtr->Fn = (screenPtr[2].x * displayPtr[1].y - screenPtr[1].x * displayPtr[2].y) * screenPtr[0].y +

                    (screenPtr[0].x * displayPtr[2].y - screenPtr[2].x * displayPtr[0].y) * screenPtr[1].y +

                    (screenPtr[1].x * displayPtr[0].y - screenPtr[0].x * displayPtr[1].y) * screenPtr[2].y ;

    // Persist data to EEPROM

    // eepromWriteS32(CFG_EEPROM_TOUCHSCREEN_CAL_AN, matrixPtr->An);

    // eepromWriteS32(CFG_EEPROM_TOUCHSCREEN_CAL_BN, matrixPtr->Bn);

    // eepromWriteS32(CFG_EEPROM_TOUCHSCREEN_CAL_CN, matrixPtr->Cn);

    // eepromWriteS32(CFG_EEPROM_TOUCHSCREEN_CAL_DN, matrixPtr->Dn);

    // eepromWriteS32(CFG_EEPROM_TOUCHSCREEN_CAL_EN, matrixPtr->En);

    // eepromWriteS32(CFG_EEPROM_TOUCHSCREEN_CAL_FN, matrixPtr->Fn);

    // eepromWriteS32(CFG_EEPROM_TOUCHSCREEN_CAL_DIVIDER, matrixPtr->Divider);

    // eepromWriteU8(CFG_EEPROM_TOUCHSCREEN_CALIBRATED, 1);

  }

  return( retValue ) ;

}

/**************************************************************************/

/*!

    @brief  Converts raw touch screen locations (screenPtr) into actual

            pixel locations on the display (displayPtr) using the

            supplied matrix.

    @param[out] displayPtr  Pointer to the tsPoint_t object that will hold

                            the compensated pixel location on the display

    @param[in]  screenPtr   Pointer to the tsPoint_t object that contains the

                            raw touch screen co-ordinates (before the

                            calibration calculations are made)

    @param[in]  matrixPtr   Pointer to the calibration matrix coefficients

                            used during the calibration process (calculated

                            via the tsCalibrate() helper function)

    @note  This is based on the public domain touch screen calibration code

           written by Carlos E. Vidales (copyright (c) 2001).

*/

/**************************************************************************/

int calibrateTSPoint( tsPoint_t * displayPtr, tsPoint_t * screenPtr, tsMatrix_t * matrixPtr )

{

  int  retValue = 0 ;

  if( matrixPtr->Divider != 0 )

  {

    displayPtr->x = ( (matrixPtr->An * screenPtr->x) +

                      (matrixPtr->Bn * screenPtr->y) +

                       matrixPtr->Cn

                    ) / matrixPtr->Divider ;

    displayPtr->y = ( (matrixPtr->Dn * screenPtr->x) +

                      (matrixPtr->En * screenPtr->y) +

                       matrixPtr->Fn

                    ) / matrixPtr->Divider ;

  }

  else

  {

    return -1;

  }

  return( retValue );

}

/**************************************************************************/

/*!

    @brief  Waits for a touch event

*/

/**************************************************************************/

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;

  }

}

/**************************************************************************/

/*!

    @brief  Renders the calibration screen with an appropriately

            placed test point and waits for a touch event

*/

/**************************************************************************/

tsPoint_t renderCalibrationScreen(uint16_t x, uint16_t y, uint16_t radius)

{

  tft.fillScreen(RA8875_WHITE);

  tft.drawCircle(x, y, radius, RA8875_RED);

  tft.drawCircle(x, y, radius + 2, 0x8410);  /* 50% Gray */

  // Wait for a valid touch events

  tsPoint_t point = { 0, 0 };

  /* Keep polling until the TS event flag is valid */

  bool valid = false;

  while (!valid)

  {

    waitForTouchEvent(&point);

    if (point.x || point.y)

    {

      valid = true;

    }

  }

  return point;

}

/**************************************************************************/

/*!

    @brief  Starts the screen calibration process.  Each corner will be

            tested, meaning that each boundary (top, left, right and

            bottom) will be tested twice and the readings averaged.

*/

/**************************************************************************/

void tsCalibrate(void)

{

  tsPoint_t data;

  /* --------------- Welcome Screen --------------- */

  Serial.println("Starting the calibration process");

  data = renderCalibrationScreen(tft.width() / 2, tft.height() / 2, 5);

  delay(250);

  /* ----------------- First Dot ------------------ */

  // 10% over and 10% down

  data = renderCalibrationScreen(tft.width() / 10, tft.height() / 10, 5);

  _tsLCDPoints[0].x = tft.width() / 10;

  _tsLCDPoints[0].y = tft.height() / 10;

  _tsTSPoints[0].x = data.x;

  _tsTSPoints[0].y = data.y;

  Serial.print("Point 1 - LCD");

  Serial.print(" X: ");

  Serial.print(_tsLCDPoints[0].x);

  Serial.print(" Y: ");

  Serial.print(_tsLCDPoints[0].y);

  Serial.print(" TS X: ");

  Serial.print(_tsTSPoints[0].x);

  Serial.print(" Y: ");

  Serial.println(_tsTSPoints[0].y);

  delay(250);

  /* ---------------- Second Dot ------------------ */

  // 50% over and 90% down

  data = renderCalibrationScreen(tft.width() / 2, tft.height() - tft.height() / 10, 5);

  _tsLCDPoints[1].x = tft.width() / 2;

  _tsLCDPoints[1].y = tft.height() - tft.height() / 10;

  _tsTSPoints[1].x = data.x;

  _tsTSPoints[1].y = data.y;

  Serial.print("Point 2 - LCD");

  Serial.print(" X: ");

  Serial.print(_tsLCDPoints[1].x);

  Serial.print(" Y: ");

  Serial.print(_tsLCDPoints[1].y);

  Serial.print(" TS X: ");

  Serial.print(_tsTSPoints[1].x);

  Serial.print(" Y: ");

  Serial.println(_tsTSPoints[1].y);

  delay(250);

  /* ---------------- Third Dot ------------------- */

  // 90% over and 50% down

  data = renderCalibrationScreen(tft.width() - tft.width() / 10, tft.height() / 2, 5);

  _tsLCDPoints[2].x = tft.width() - tft.width() / 10;

  _tsLCDPoints[2].y = tft.height() / 2;

  _tsTSPoints[2].x = data.x;

  _tsTSPoints[2].y = data.y;

  Serial.print("Point 3 - LCD");

  Serial.print(" X: ");

  Serial.print(_tsLCDPoints[2].x);

  Serial.print(" Y: ");

  Serial.print(_tsLCDPoints[2].y);

  Serial.print(" TS X: ");

  Serial.print(_tsTSPoints[2].x);

  Serial.print(" Y: ");

  Serial.println(_tsTSPoints[2].y);

  delay(250);

  /* Clear the screen */

  tft.fillScreen(RA8875_WHITE);

  // Do matrix calculations for calibration and store to EEPROM

  setCalibrationMatrix(&_tsLCDPoints[0], &_tsTSPoints[0], &_tsMatrix);

}

/**************************************************************************/

/*!

*/

/**************************************************************************/

void setup()

{

  Serial.begin(9600);

  Serial.println("Hello, RA8875!");

  /* Initialise the display using 'RA8875_480x272' or 'RA8875_800x480' */

    if (!tft.begin(RA8875_480x272))

  {

    Serial.println("RA8875 not found ... check your wires!");

    while (1);

  }

  /* Enables the display and sets up the backlight */

  Serial.println("Found RA8875");

  tft.displayOn(true);

  tft.GPIOX(true); // Enable TFT - display enable tied to GPIOX

  tft.PWM1config(true, RA8875_PWM_CLK_DIV1024); // PWM output for backlight

  tft.PWM1out(255);

  /* Enable the touch screen */

  Serial.println("Enabled the touch screen");

  pinMode(RA8875_INT, INPUT);

  digitalWrite(RA8875_INT, HIGH);

  tft.touchEnable(true);

  // Try some GFX acceleration!

  //tft.drawCircle(100, 100, 50, RA8875_BLACK);

  //tft.fillCircle(100, 100, 49, RA8875_GREEN);

  //tft.drawPixel(10,10,RA8875_BLACK);

  //tft.drawPixel(11,11,RA8875_BLACK);

  //tft.drawRect(10, 10, 400, 200, RA8875_GREEN);

  //tft.fillRect(11, 11, 398, 198, RA8875_BLUE);

  //tft.drawLine(10, 10, 200, 100, RA8875_RED);

  tft.fillScreen(RA8875_WHITE);

  delay(100);

  /* Start the calibration process */

  tsCalibrate();

  /* _tsMatrix should now be populated with the correct coefficients! */

  Serial.println("Waiting for touch events ...");

}

/**************************************************************************/

/*!

*/

/**************************************************************************/

void loop()

{

  tsPoint_t raw;

  tsPoint_t calibrated;

  /* Wait around for a touch event */

  waitForTouchEvent(&raw);

  /* Calcuate the real X/Y position based on the calibration matrix */

  calibrateTSPoint(&calibrated, &raw, &_tsMatrix );

  /* Draw a single pixel at the calibrated point */

  tft.fillCircle(calibrated.x, calibrated.y, 3, RA8875_BLACK);

}

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,