Library to control a Graphics TFT connected to 4-wire SPI - revised for the Raio RA8875 Display Controller.

Dependents:   FRDM_RA8875_mPaint RA8875_Demo RA8875_KeyPadDemo RA8875_Demo ... more

Fork of SPI_TFT by Peter Drescher

See Components - RA8875 Based Display

Enhanced touch-screen support - where it previous supported both the Resistive Touch and Capacitive Touch based on the FT5206 Touch Controller, now it also has support for the GSL1680 Touch Controller.

Offline Help Manual (Windows chm)

/media/uploads/WiredHome/ra8875.zip.bin (download, rename to .zip and unzip)

RA8875_Touch.cpp

Committer:
WiredHome
Date:
2016-11-16
Revision:
136:224e03d5c31f
Parent:
130:d633e80840e0
Child:
145:5eb2492acdda

File content as of revision 136:224e03d5c31f:

/// This file contains the RA8875 Touch panel methods.
///
/// It combines both resistive and capacitive touch methods, and tries
/// to make them nearly transparent alternates for each other.
///
#include "RA8875.h"

#define NOTOUCH_TIMEOUT_uS 100000
#define TOUCH_TICKER_uS      1000


// Translate from FT5206 Event Flag to Touch Code to API-match the
// alternate resistive touch screen driver common in the RA8875
// displays.
static const TouchCode_t EventFlagToTouchCode[4] = {
    touch,      // 00b Put Down
    release,    // 01b Put Up
    held,       // 10b Contact
    no_touch    // 11b Reserved
};


RetCode_t RA8875::TouchPanelInit(void)
{
    panelTouched = false;
    if (useTouchPanel == TP_CAP) {
        // Set to normal mode
        writeRegister8(FT5206_DEVICE_MODE, 0);
    } else {
        //TPCR0: Set enable bit, default sample time, wakeup, and ADC clock
        WriteCommand(TPCR0, TP_ENABLE | TP_ADC_SAMPLE_DEFAULT_CLKS | TP_ADC_CLKDIV_DEFAULT);
        // TPCR1: Set auto/manual, Ref voltage, debounce, manual mode params
        WriteCommand(TPCR1, TP_MODE_DEFAULT | TP_DEBOUNCE_DEFAULT);
        WriteCommand(INTC1, ReadCommand(INTC1) | RA8875_INT_TP);        // reg INTC1: Enable Touch Panel Interrupts (D2 = 1)
        WriteCommand(INTC2, RA8875_INT_TP);                            // reg INTC2: Clear any TP interrupt flag
        touchSample = 0;
        touchState = no_cal;
        touchTicker.attach_us(this, &RA8875::_TouchTicker, TOUCH_TICKER_uS);
        touchTimer.start();
        touchTimer.reset();
    }
    return noerror;
}


RetCode_t RA8875::TouchPanelInit(uint8_t bTpEnable, uint8_t bTpAutoManual, uint8_t bTpDebounce, uint8_t bTpManualMode, uint8_t bTpAdcClkDiv, uint8_t bTpAdcSampleTime)
{
    if (useTouchPanel == TP_CAP) {
        TouchPanelInit();
    } else {
        // Parameter bounds check
        if( \
                !(bTpEnable == TP_ENABLE || bTpEnable == TP_ENABLE) || \
                !(bTpAutoManual == TP_MODE_AUTO || bTpAutoManual == TP_MODE_MANUAL) || \
                !(bTpDebounce == TP_DEBOUNCE_OFF || bTpDebounce == TP_DEBOUNCE_ON) || \
                !(bTpManualMode <= TP_MANUAL_LATCH_Y) || \
                !(bTpAdcClkDiv <= TP_ADC_CLKDIV_128) || \
                !(bTpAdcSampleTime <= TP_ADC_SAMPLE_65536_CLKS) \
          ) return bad_parameter;
        // Construct the config byte for TPCR0 and write them
        WriteCommand(TPCR0, bTpEnable | bTpAdcClkDiv | bTpAdcSampleTime);    // Note: Wakeup is never enabled
        // Construct the config byte for TPCR1 and write them
        WriteCommand(TPCR1, bTpManualMode | bTpDebounce | bTpManualMode);    // Note: Always uses internal Vref.
        // Set up the interrupt flag and enable bits
        WriteCommand(INTC1, ReadCommand(INTC1) | RA8875_INT_TP);        // reg INTC1: Enable Touch Panel Interrupts (D2 = 1)
        WriteCommand(INTC2, RA8875_INT_TP);                            // reg INTC2: Clear any TP interrupt flag
        touchSample = 0;
        touchState = no_cal;
        if (bTpEnable == TP_ENABLE) {
            touchTicker.attach_us(this, &RA8875::_TouchTicker, TOUCH_TICKER_uS);
            touchTimer.start();
            touchTimer.reset();
        } else {
            touchTicker.detach();
            touchTimer.stop();
        }
    }
    return noerror;
}


int RA8875::TouchChannels(void)
{
    if (useTouchPanel == TP_CAP) {
        return 5;   // based on the FT5206 hardware
    } else if (useTouchPanel == TP_RES) {
        return 1;   // based on the RA8875 resistive touch driver
    } else {
        return 0;   // it isn't enabled, so there are none.
    }
}


// +----------------------------------------------------+
// |                                                    |
// |  1                                                 |
// |                                                    |
// |                                                    |
// |                                               2    |
// |                                                    |
// |                                                    |
// |                         3                          |
// |                                                    |
// +----------------------------------------------------+

RetCode_t RA8875::TouchPanelCalibrate(tpMatrix_t * matrix)
{
    return TouchPanelCalibrate(NULL, matrix);
}

RetCode_t RA8875::TouchPanelCalibrate(const char * msg, tpMatrix_t * matrix, int maxwait_s)
{
    point_t pTest[3];
    point_t pSample[3];
    int x,y;
    Timer timeout;  // timeout guards for not-installed, stuck, user not present...

    timeout.start();
    while (TouchPanelA2DFiltered(&x, &y) && timeout.read() < maxwait_s) {
        wait_ms(20);
        if (idle_callback) {
            if (external_abort == (*idle_callback)(touchcal_wait)) {
                return external_abort;
            }
        }
    }
    cls();
    if (msg)
        puts(msg);
    SetTextCursor(0,height()/2);
    pTest[0].x = 50;
    pTest[0].y = 50;
    pTest[1].x = width() - 50;
    pTest[1].y = height()/2;
    pTest[2].x = width()/2;
    pTest[2].y = height() - 50;

    for (int i=0; i<3; i++) {
        foreground(Blue);
        printf(" (%3d,%3d) => ", pTest[i].x, pTest[i].y);
        line(pTest[i].x-10, pTest[i].y, pTest[i].x+10, pTest[i].y, White);
        line(pTest[i].x, pTest[i].y-10, pTest[i].x, pTest[i].y+10, White);
        while (!TouchPanelA2DFiltered(&x, &y) && timeout.read() < maxwait_s) {
            wait_ms(20);
            if (idle_callback) {
                if (external_abort == (*idle_callback)(touchcal_wait)) {
                    return external_abort;
                }
            }
        }
        pSample[i].x = x;
        pSample[i].y = y;
        line(pTest[i].x-10, pTest[i].y, pTest[i].x+10, pTest[i].y, Black);
        line(pTest[i].x, pTest[i].y-10, pTest[i].x, pTest[i].y+10, Black);
        foreground(Blue);
        printf(" (%4d,%4d)\r\n", x,y);
        while (TouchPanelA2DFiltered(&x, &y) && timeout.read() < maxwait_s) {
            wait_ms(20);
            if (idle_callback) {
                if (external_abort == (*idle_callback)(touchcal_wait)) {
                    return external_abort;
                }
            }
        }
        for (int t=0; t<100; t++) {
            wait_ms(20);
            if (idle_callback) {
                if (external_abort == (*idle_callback)(touchcal_wait)) {
                    return external_abort;
                }
            }
        }
    }
    if (timeout.read() >= maxwait_s)
        return touch_cal_timeout;
    else
        return TouchPanelComputeCalibration(pTest, pSample, matrix);
}


/**********************************************************************
 *
 *     Function: TouchPanelReadable()
 *
 *  Description: Given a valid set of calibration factors and a point
 *                value reported by the touch screen, this function
 *                calculates and returns the true (or closest to true)
 *                display point below the spot where the touch screen
 *                was touched.
 *
 *
 *
 *  Argument(s): displayPtr (output) - Pointer to the calculated
 *                                      (true) display point.
 *               screenPtr (input) - Pointer to the reported touch
 *                                    screen point.
 *               matrixPtr (input) - Pointer to calibration factors
 *                                    matrix previously calculated
 *                                    from a call to
 *                                    setCalibrationMatrix()
 *
 *
 *  The function simply solves for Xd and Yd by implementing the
 *   computations required by the translation matrix.
 *
 *                                              /-     -\
 *              /-    -\     /-            -\   |       |
 *              |      |     |              |   |   Xs  |
 *              |  Xd  |     | A    B    C  |   |       |
 *              |      |  =  |              | * |   Ys  |
 *              |  Yd  |     | D    E    F  |   |       |
 *              |      |     |              |   |   1   |
 *              \-    -/     \-            -/   |       |
 *                                              \-     -/
 *
 *  It must be kept brief to avoid consuming CPU cycles.
 *
 *       Return: OK - the display point was correctly calculated
 *                     and its value is in the output argument.
 *               NOT_OK - an error was detected and the function
 *                         failed to return a valid point.
 *
 *                 NOTE!    NOTE!    NOTE!
 *
 *  setCalibrationMatrix() and getDisplayPoint() will do fine
 *  for you as they are, provided that your digitizer
 *  resolution does not exceed 10 bits (1024 values).  Higher
 *  resolutions may cause the integer operations to overflow
 *  and return incorrect values.  If you wish to use these
 *  functions with digitizer resolutions of 12 bits (4096
 *  values) you will either have to a) use 64-bit signed
 *  integer variables and math, or b) judiciously modify the
 *  operations to scale results by a factor of 2 or even 4.
 *
 */
TouchCode_t RA8875::TouchPanelReadable(point_t * TouchPoint)
{
    TouchCode_t ts = no_touch;

    if (useTouchPanel == TP_RES) {
        int a2dX = 0;
        int a2dY = 0;
        
        touchInfo[0].touchID = 0;
        ts = TouchPanelA2DFiltered(&a2dX, &a2dY);
        if (ts != no_touch) {
            panelTouched = true;
            numberOfTouchPoints = 1;

            if (tpMatrix.Divider != 0) {
                /* Operation order is important since we are doing integer */
                /*  math. Make sure you add all terms together before      */
                /*  dividing, so that the remainder is not rounded off     */
                /*  prematurely.                                           */
                touchInfo[0].coordinates.x = ( (tpMatrix.An * a2dX) +
                                  (tpMatrix.Bn * a2dY) + tpMatrix.Cn
                                ) / tpMatrix.Divider ;
                touchInfo[0].coordinates.y = ( (tpMatrix.Dn * a2dX) +
                                  (tpMatrix.En * a2dY) + tpMatrix.Fn
                                ) / tpMatrix.Divider ;
            } else {
                ts = no_cal;
            }
        } else {
            numberOfTouchPoints = 0;
        }
        touchInfo[0].touchCode = ts;
    } else /* (useTouchPanel == TP_CAP) */ {
        ;
    }
    if (panelTouched == true) {
        panelTouched = false;
        if (TouchPoint) {
            *TouchPoint = touchInfo[0].coordinates;
            ts = touchInfo[0].touchCode;
        } else {
            ts = touch;
        }
    }
    return ts;
}


TouchCode_t RA8875::TouchPanelGet(point_t * TouchPoint)
{
    TouchCode_t t = no_touch;

    while (true) {
        t = TouchPanelReadable(TouchPoint);
        if (t != no_touch)
            break;
        if (idle_callback) {
            if (external_abort == (*idle_callback)(touch_wait)) {
                return no_touch;
            }
        }
    }
    return t;
}

// Below here are primarily "helper" functions. While many are accessible
// to the user code, they usually don't need to be called.

RetCode_t RA8875::TouchPanelSetMatrix(tpMatrix_t * matrixPtr)
{
    if (matrixPtr == NULL || matrixPtr->Divider == 0)
        return bad_parameter;
    memcpy(&tpMatrix, matrixPtr, sizeof(tpMatrix_t));
    touchState = no_touch;
    return noerror;
}

static void InsertionSort(int * buf, int bufsize)
{
    int i, j;
    int temp;

    for(i = 1; i < bufsize; i++) {
        temp = buf[i];
        j = i;
        while( j && (buf[j-1] > temp) ) {
            buf[j] = buf[j-1];
            j = j-1;
        }
        buf[j] = temp;
    } // End of sort
}


void RA8875::_TouchTicker(void)
{
    if (touchTimer.read_us() > NOTOUCH_TIMEOUT_uS) {
        touchSample = 0;
        if (touchState == held)
            touchState = release;
        else
            touchState = no_touch;
        touchTimer.reset();
    }
}

TouchCode_t RA8875::TouchPanelA2DRaw(int *x, int *y)
{
    if( (ReadCommand(INTC2) & RA8875_INT_TP) ) {        // Test for TP Interrupt pending in register INTC2
        touchTimer.reset();
        *y = ReadCommand(TPYH) << 2 | ( (ReadCommand(TPXYL) & 0xC) >> 2 );   // D[9:2] from reg TPYH, D[1:0] from reg TPXYL[3:2]
        *x = ReadCommand(TPXH) << 2 | ( (ReadCommand(TPXYL) & 0x3)      );   // D[9:2] from reg TPXH, D[1:0] from reg TPXYL[1:0]
        WriteCommand(INTC2, RA8875_INT_TP);            // reg INTC2: Clear that TP interrupt flag
        touchState = touch;
    } else {
        touchState = no_touch;
    }
    return touchState;
}

TouchCode_t RA8875::TouchPanelA2DFiltered(int *x, int *y)
{
    static int xbuf[TPBUFSIZE], ybuf[TPBUFSIZE];
    static int lastX, lastY;
    int i, j;
    TouchCode_t ret = touchState;

    if( (ReadCommand(INTC2) & RA8875_INT_TP) ) {        // Test for TP Interrupt pending in register INTC2
        touchTimer.reset();
        // Get the next data samples
        ybuf[touchSample] =  ReadCommand(TPYH) << 2 | ( (ReadCommand(TPXYL) & 0xC) >> 2 );   // D[9:2] from reg TPYH, D[1:0] from reg TPXYL[3:2]
        xbuf[touchSample] =  ReadCommand(TPXH) << 2 | ( (ReadCommand(TPXYL) & 0x3)      );   // D[9:2] from reg TPXH, D[1:0] from reg TPXYL[1:0]
        // Check for a complete set
        if(++touchSample == TPBUFSIZE) {
            // Buffers are full, so process them using Finn's method described in Analog Dialogue No. 44, Feb 2010
            // This requires sorting the samples in order of size, then discarding the top 25% and
            //   bottom 25% as noise spikes. Finally, the middle 50% of the values are averaged to
            //   reduce Gaussian noise.
#if 1
            InsertionSort(ybuf, TPBUFSIZE);
            InsertionSort(xbuf, TPBUFSIZE);
#else
            // Sort the Y buffer using an Insertion Sort
            for(i = 1; i <= TPBUFSIZE; i++) {
                temp = ybuf[i];
                j = i;
                while( j && (ybuf[j-1] > temp) ) {
                    ybuf[j] = ybuf[j-1];
                    j = j-1;
                }
                ybuf[j] = temp;
            } // End of Y sort
            // Sort the X buffer the same way
            for(i = 1; i <= TPBUFSIZE; i++) {
                temp = xbuf[i];
                j = i;
                while( j && (xbuf[j-1] > temp) ) {
                    xbuf[j] = xbuf[j-1];
                    j = j-1;
                }
                xbuf[j] = temp;
            } // End of X sort
#endif
            // Average the middle half of the  Y values and report them
            j = 0;
            for(i = (TPBUFSIZE/4) - 1; i < TPBUFSIZE - TPBUFSIZE/4; i++ ) {
                j += ybuf[i];
            }
            *y = lastY = j * (float)2/TPBUFSIZE;    // This is the average
            // Average the middle half of the  X values and report them
            j = 0;
            for(i = (TPBUFSIZE/4) - 1; i < TPBUFSIZE - TPBUFSIZE/4; i++ ) {
                j += xbuf[i];
            }
            *x = lastX = j * (float)2/TPBUFSIZE;    // This is the average
            // Tidy up and return
            if (touchState == touch || touchState == held)
                touchState = held;
            else
                touchState = touch;
            ret = touchState;
            touchSample = 0;             // Ready to start on the next set of data samples
        } else {
            // Buffer not yet full, so do not return any results yet
            if (touchState == touch || touchState == held) {
                *x = lastX;
                *y = lastY;
                ret = touchState = held;
            }
        }
        WriteCommand(INTC2, RA8875_INT_TP);            // reg INTC2: Clear that TP interrupt flag
    } // End of initial if -- data has been read and processed
    else {
        if (touchState == touch || touchState == held) {
            *x = lastX;
            *y = lastY;
            ret = touchState = held;
        } else if (touchState == release) {
            *x = lastX;
            *y = lastY;
            ret = release;
            touchState = no_touch;
        }
    }
    return ret;
}

/*   The following section is derived from Carlos E. Vidales.
 *
 *   Copyright (c) 2001, Carlos E. Vidales. All rights reserved.
 *
 *   This sample program was written and put in the public domain
 *    by Carlos E. Vidales.  The program is provided "as is"
 *    without warranty of any kind, either expressed or implied.
 *   If you choose to use the program within your own products
 *    you do so at your own risk, and assume the responsibility
 *    for servicing, repairing or correcting the program should
 *    it prove defective in any manner.
 *   You may copy and distribute the program's source code in any
 *    medium, provided that you also include in each copy an
 *    appropriate copyright notice and disclaimer of warranty.
 *   You may also modify this program and distribute copies of
 *    it provided that you include prominent notices stating
 *    that you changed the file(s) and the date of any change,
 *    and that you do not charge any royalties or licenses for
 *    its use.
 *
 *   This file contains functions that implement calculations
 *    necessary to obtain calibration factors for a touch screen
 *    that suffers from multiple distortion effects: namely,
 *    translation, scaling and rotation.
 *
 *   The following set of equations represent a valid display
 *    point given a corresponding set of touch screen points:
 *
 *                                              /-     -\
 *              /-    -\     /-            -\   |       |
 *              |      |     |              |   |   Xs  |
 *              |  Xd  |     | A    B    C  |   |       |
 *              |      |  =  |              | * |   Ys  |
 *              |  Yd  |     | D    E    F  |   |       |
 *              |      |     |              |   |   1   |
 *              \-    -/     \-            -/   |       |
 *                                              \-     -/
 *    where:
 *           (Xd,Yd) represents the desired display point
 *                    coordinates,
 *           (Xs,Ys) represents the available touch screen
 *                    coordinates, and the matrix
 *           /-   -\
 *           |A,B,C|
 *           |D,E,F| represents the factors used to translate
 *           \-   -/  the available touch screen point values
 *                    into the corresponding display
 *                    coordinates.
 *    Note that for practical considerations, the utilities
 *     within this file do not use the matrix coefficients as
 *     defined above, but instead use the following
 *     equivalents, since floating point math is not used:
 *            A = An/Divider
 *            B = Bn/Divider
 *            C = Cn/Divider
 *            D = Dn/Divider
 *            E = En/Divider
 *            F = Fn/Divider
 *    The functions provided within this file are:
 *          setCalibrationMatrix() - calculates the set of factors
 *                                    in the above equation, given
 *                                    three sets of test points.
 *               getDisplayPoint() - returns the actual display
 *                                    coordinates, given a set of
 *                                    touch screen coordinates.
 * translateRawScreenCoordinates() - helper function to transform
 *                                    raw screen points into values
 *                                    scaled to the desired display
 *                                    resolution.
 */

/**********************************************************************
 *
 *     Function: setCalibrationMatrix()
 *
 *  Description: Calling this function with valid input data
 *                in the display and screen input arguments
 *                causes the calibration factors between the
 *                screen and display points to be calculated,
 *                and the output argument - matrixPtr - to be
 *                populated.
 *
 *               This function needs to be called only when new
 *                calibration factors are desired.
 *
 *
 *  Argument(s): displayPtr (input) - Pointer to an array of three
 *                                     sample, reference points.
 *               screenPtr (input) - Pointer to the array of touch
 *                                    screen points corresponding
 *                                    to the reference display points.
 *               matrixPtr (output) - Pointer to the calibration
 *                                     matrix computed for the set
 *                                     of points being provided.
 *
 *
 *  From the article text, recall that the matrix coefficients are
 *   resolved to be the following:
 *
 *
 *      Divider =  (Xs0 - Xs2)*(Ys1 - Ys2) - (Xs1 - Xs2)*(Ys0 - Ys2)
 *
 *
 *
 *                 (Xd0 - Xd2)*(Ys1 - Ys2) - (Xd1 - Xd2)*(Ys0 - Ys2)
 *            A = ---------------------------------------------------
 *                                   Divider
 *
 *
 *                 (Xs0 - Xs2)*(Xd1 - Xd2) - (Xd0 - Xd2)*(Xs1 - Xs2)
 *            B = ---------------------------------------------------
 *                                   Divider
 *
 *
 *                 Ys0*(Xs2*Xd1 - Xs1*Xd2) +
 *                             Ys1*(Xs0*Xd2 - Xs2*Xd0) +
 *                                           Ys2*(Xs1*Xd0 - Xs0*Xd1)
 *            C = ---------------------------------------------------
 *                                   Divider
 *
 *
 *                 (Yd0 - Yd2)*(Ys1 - Ys2) - (Yd1 - Yd2)*(Ys0 - Ys2)
 *            D = ---------------------------------------------------
 *                                   Divider
 *
 *
 *                 (Xs0 - Xs2)*(Yd1 - Yd2) - (Yd0 - Yd2)*(Xs1 - Xs2)
 *            E = ---------------------------------------------------
 *                                   Divider
 *
 *
 *                 Ys0*(Xs2*Yd1 - Xs1*Yd2) +
 *                             Ys1*(Xs0*Yd2 - Xs2*Yd0) +
 *                                           Ys2*(Xs1*Yd0 - Xs0*Yd1)
 *            F = ---------------------------------------------------
 *                                   Divider
 *
 *
 *       Return: OK - the calibration matrix was correctly
 *                     calculated and its value is in the
 *                     output argument.
 *               NOT_OK - an error was detected and the
 *                         function failed to return a valid
 *                         set of matrix values.
 *                        The only time this sample code returns
 *                        NOT_OK is when Divider == 0
 *
 *
 *
 *                 NOTE!    NOTE!    NOTE!
 *
 *  setCalibrationMatrix() and getDisplayPoint() will do fine
 *  for you as they are, provided that your digitizer
 *  resolution does not exceed 10 bits (1024 values).  Higher
 *  resolutions may cause the integer operations to overflow
 *  and return incorrect values.  If you wish to use these
 *  functions with digitizer resolutions of 12 bits (4096
 *  values) you will either have to a) use 64-bit signed
 *  integer variables and math, or b) judiciously modify the
 *  operations to scale results by a factor of 2 or even 4.
 *
 */
RetCode_t RA8875::TouchPanelComputeCalibration(point_t * displayPtr, point_t * screenPtr, tpMatrix_t * matrixPtr)
{
    RetCode_t retValue = noerror;

    tpMatrix.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( tpMatrix.Divider == 0 )  {
        retValue = bad_parameter;
    }  else   {
        tpMatrix.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)) ;

        tpMatrix.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)) ;

        tpMatrix.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 ;

        tpMatrix.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)) ;

        tpMatrix.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)) ;

        tpMatrix.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 ;
        touchState = no_touch;
        if (matrixPtr)
            memcpy(matrixPtr, &tpMatrix, sizeof(tpMatrix_t));
    }
    return( retValue ) ;
}

////////////////// Capacitive Touch Panel

uint8_t RA8875::readRegister8(uint8_t reg) {
    char val;
    
    m_i2c->write(m_addr, (const char *)&reg, 1);
    m_i2c->read(m_addr, &val, 1);
    return (uint8_t)val;
}

void RA8875::writeRegister8(uint8_t reg, uint8_t val) {
    char data[2];
    
    data[0] = (char)reg;
    data[1] = (char)val;
    m_i2c->write((int)FT5206_I2C_ADDRESS, data, 2);
}


// Interrupt for touch detection
void RA8875::TouchPanelISR(void)
{
    getTouchPositions();
    panelTouched = true;
}

uint8_t RA8875::getTouchPositions(void) {
    uint8_t valXH;
    uint8_t valYH;

    numberOfTouchPoints = readRegister8(FT5206_TD_STATUS) & 0xF;
    gesture = readRegister8(FT5206_GEST_ID);
    
    // If the switch statement was based only on numberOfTouchPoints, it would not
    // be able to generate notification for 'release' events (as it is no longer touched).
    // Therefore, forcing a 5, and it intentially falls through each lower case.
    switch (5) {    // numberOfTouchPoints
        case 5:
            valXH  = readRegister8(FT5206_TOUCH5_XH);
            valYH  = readRegister8(FT5206_TOUCH5_YH);
            touchInfo[4].touchCode = EventFlagToTouchCode[valXH >> 6];
            touchInfo[4].touchID   = (valYH >> 4);
            touchInfo[4].coordinates.x = (valXH & 0x0f)*256 + readRegister8(FT5206_TOUCH5_XL);
            touchInfo[4].coordinates.y = (valYH & 0x0f)*256 + readRegister8(FT5206_TOUCH5_YL);
        case 4:
            valXH  = readRegister8(FT5206_TOUCH4_XH);
            valYH  = readRegister8(FT5206_TOUCH4_YH);
            touchInfo[3].touchCode = EventFlagToTouchCode[valXH >> 6];
            touchInfo[3].touchID   = (valYH >> 4);
            touchInfo[3].coordinates.x = (readRegister8(FT5206_TOUCH4_XH) & 0x0f)*256 + readRegister8(FT5206_TOUCH4_XL);
            touchInfo[3].coordinates.y = (valYH & 0x0f)*256 + readRegister8(FT5206_TOUCH4_YL);
        case 3:
            valXH  = readRegister8(FT5206_TOUCH3_XH);
            valYH  = readRegister8(FT5206_TOUCH3_YH);
            touchInfo[2].touchCode = EventFlagToTouchCode[valXH >> 6];
            touchInfo[2].touchID   = (valYH >> 4);
            touchInfo[2].coordinates.x = (readRegister8(FT5206_TOUCH3_XH) & 0x0f)*256 + readRegister8(FT5206_TOUCH3_XL);
            touchInfo[2].coordinates.y = (valYH & 0x0f)*256 + readRegister8(FT5206_TOUCH3_YL);
        case 2:
            valXH  = readRegister8(FT5206_TOUCH2_XH);
            valYH  = readRegister8(FT5206_TOUCH2_YH);
            touchInfo[1].touchCode = EventFlagToTouchCode[valXH >> 6];
            touchInfo[1].touchID   = (valYH >> 4);
            touchInfo[1].coordinates.x  = (readRegister8(FT5206_TOUCH2_XH) & 0x0f)*256 + readRegister8(FT5206_TOUCH2_XL);
            touchInfo[1].coordinates.y  = (valYH & 0x0f)*256 + readRegister8(FT5206_TOUCH2_YL);
        case 1:
            valXH  = readRegister8(FT5206_TOUCH1_XH);
            valYH  = readRegister8(FT5206_TOUCH1_YH);
            touchInfo[0].touchCode = EventFlagToTouchCode[valXH >> 6];
            touchInfo[0].touchID   = (valYH >> 4);
            touchInfo[0].coordinates.x = (readRegister8(FT5206_TOUCH1_XH) & 0x0f)*256 + readRegister8(FT5206_TOUCH1_XL);
            touchInfo[0].coordinates.y = (valYH & 0x0f)*256 + readRegister8(FT5206_TOUCH1_YL);
            break;
        default:
            break;
    }
    return numberOfTouchPoints;
}

// #### end of touch panel code additions