/**
* \brief Performs the calibration process using the provided buffer to display
* information.
*
* \return True if calibration was successful; otherwise false.
*/
uint8_t TSDCom_Calibrate(void)
{
volatile uint32_t i; /* to keep the tempo with gcc code optimisation */
int32_t slope1, slope2;
CalibrationPoint measuredPoint;
uint8_t xOk, yOk;
int32_t xDiff, yDiff;
/* Calibration setup */
LCDD_Fill(COLOR_WHITE);
LCDD_DrawString(30, 50, (uint8_t *)"LCD calibration", COLOR_BLACK);
LCDD_DrawString(1, 140, (uint8_t *)"Touch the dots to\ncalibrate the screen", COLOR_DARKBLUE);
/* Calibration points */
for (i=0; i < 4; i++) {
DrawCalibrationPoint(&calibrationPoints[i]);
/* Wait for touch & end of conversion */
TSD_WaitPenPressed();
TSD_GetRawMeasurement(calibrationPoints[i].data);
ClearCalibrationPoint(&calibrationPoints[i]);
/* Wait for contact loss */
TSD_WaitPenReleased();
}
/**
* Calculate slopes using the calibration data
* Theory behind those calculations:
* - We suppose the touchscreen measurements are linear, so the following equations are true (simple
* linear regression) for any two 'a' and 'b' points of the screen:
* dx = (a.data[0] - b.data[0]) / (a.x - b.x)
* dy = (a.data[1] - b.data[1]) / (a.y - b.y)
*
* - We calculate dx and dy (called xslope and yslope here) using the calibration points.
*
* - We can then use dx and dy to infer the position of a point 'p' given the measurements performed
* by the touchscreen ('c' is any of the calibration points):
* dx = (p.data[0] - c.data[0]) / (p.x - c.x)
* dy = (p.data[1] - c.data[1]) / (p.y - c.y)
* Thus:
* p.x = c.x - (p.data[0] - c.data[0]) / dx
* p.y = c.y - (p.data[1] - c.data[1]) / dy
*
* - Since there are four calibration points, dx and dy can be calculated twice, so we average
* the two values.
*/
slope1 = ((int32_t) calibrationPoints[0].data[0]) - ((int32_t) calibrationPoints[1].data[0]);
slope1 *= 1024;
slope1 /= ((int32_t) calibrationPoints[0].x) - ((int32_t) calibrationPoints[1].x);
slope2 = ((int32_t) calibrationPoints[2].data[0]) - ((int32_t) calibrationPoints[3].data[0]);
slope2 *= 1024;
slope2 /= ((int32_t) calibrationPoints[2].x) - ((int32_t) calibrationPoints[3].x);
xSlope = (slope1 + slope2) / 2;
slope1 = ((int32_t) calibrationPoints[0].data[1]) - ((int32_t) calibrationPoints[2].data[1]);
slope1 *= 1024;
slope1 /= ((int32_t) calibrationPoints[0].y) - ((int32_t) calibrationPoints[2].y);
slope2 = ((int32_t) calibrationPoints[1].data[1]) - ((int32_t) calibrationPoints[3].data[1]);
slope2 *= 1024;
slope2 /= ((int32_t) calibrationPoints[1].y) - ((int32_t) calibrationPoints[3].y);
ySlope = (slope1 + slope2) / 2;
/* Test point */
LCDD_Fill(0xFFFFFF);
LCDD_DrawString(30, 50, (uint8_t *)"LCD calibration", COLOR_BLACK);
LCDD_DrawString(1, 100, (uint8_t *)" Touch the point to\nvalidate calibration", COLOR_DARKBLUE);
DrawCalibrationPoint(&testPoint);
/* Wait for touch & end of conversion */
TSD_WaitPenPressed();
TSD_GetRawMeasurement(measuredPoint.data);
TSDCom_InterpolateMeasurement(measuredPoint.data, (uint32_t *) &measuredPoint);
DrawCalibrationPoint(&measuredPoint);
/* Check resulting x and y */
xDiff = (int32_t) measuredPoint.x - (int32_t) testPoint.x;
yDiff = (int32_t) measuredPoint.y - (int32_t) testPoint.y;
xOk = (xDiff >= -POINTS_MAX_ERROR) && (xDiff <= POINTS_MAX_ERROR);
yOk = (yDiff >= -POINTS_MAX_ERROR) && (yDiff <= POINTS_MAX_ERROR);
/* Wait for contact loss */
TSD_WaitPenReleased();
/* Check calibration result */
if (xOk && yOk) {
bCalibrationOk = 1;
LCDD_Fill(COLOR_WHITE);
LCDD_DrawString(30, 50, (uint8_t *)"LCD calibration", COLOR_BLACK);
LCDD_DrawString(80, 140, (uint8_t *)"Success !", COLOR_GREEN);
}
else {
bCalibrationOk = 0;
LCDD_Fill(COLOR_WHITE);
LCDD_DrawString(30, 50, (uint8_t *)"LCD calibration", COLOR_BLACK);
LCDD_DrawString(40, 140, (uint8_t *)"Error too big", COLOR_RED);
}
/* Slight delay */
for (i = 0; i < DELAY_RESULT_DISPLAY; i++);
return (xOk && yOk);
}
//------------------------------------------------------------------------------
/// Performs the calibration process using the provided buffer to display
/// information.
/// \param pLcdBuffer LCD buffer to display.
/// \return True if calibration was successful; otherwise false.
//------------------------------------------------------------------------------
unsigned char TSDCom_Calibrate(void *pLcdBuffer)
{
#ifdef AT91C_ID_LCDC
void *pOldLcdBuffer;
#endif
volatile unsigned int i; // to keep the tempo with gcc code optimisation
signed int slope1, slope2;
CalibrationPoint measuredPoint;
unsigned char xOk, yOk;
signed int xDiff, yDiff;
// Calibration setup
LCDD_Fill(pLcdBuffer, COLOR_WHITE);
LCDD_DrawString(pLcdBuffer, 30, 50, "LCD calibration", COLOR_BLACK);
LCDD_DrawString(pLcdBuffer, 1, 100, " Touch the dots to\ncalibrate the screen", COLOR_DARKBLUE);
#ifdef AT91C_ID_LCDC
pOldLcdBuffer = LCDD_DisplayBuffer(pLcdBuffer);
#endif
// Calibration points
for (i=0; i < 4; i++) {
DrawCalibrationPoint(pLcdBuffer, &calibrationPoints[i]);
// Wait for touch & end of conversion
TSD_WaitPenPressed();
TSD_GetRawMeasurement(calibrationPoints[i].data);
ClearCalibrationPoint(pLcdBuffer, &calibrationPoints[i]);
// Wait for contact loss
TSD_WaitPenReleased();
}
// Calculate slopes using the calibration data
// Theory behind those calculations:
// - We suppose the touchscreen measurements are linear, so the following equations are true (simple
// linear regression) for any two 'a' and 'b' points of the screen:
// dx = (a.data[0] - b.data[0]) / (a.x - b.x)
// dy = (a.data[1] - b.data[1]) / (a.y - b.y)
//
// - We calculate dx and dy (called xslope and yslope here) using the calibration points.
//
// - We can then use dx and dy to infer the position of a point 'p' given the measurements performed
// by the touchscreen ('c' is any of the calibration points):
// dx = (p.data[0] - c.data[0]) / (p.x - c.x)
// dy = (p.data[1] - c.data[1]) / (p.y - c.y)
// Thus:
// p.x = c.x - (p.data[0] - c.data[0]) / dx
// p.y = c.y - (p.data[1] - c.data[1]) / dy
//
// - Since there are four calibration points, dx and dy can be calculated twice, so we average
// the two values.
slope1 = ((signed int) calibrationPoints[0].data[0]) - ((signed int) calibrationPoints[1].data[0]);
slope1 *= 1024;
slope1 /= ((signed int) calibrationPoints[0].x) - ((signed int) calibrationPoints[1].x);
slope2 = ((signed int) calibrationPoints[2].data[0]) - ((signed int) calibrationPoints[3].data[0]);
slope2 *= 1024;
slope2 /= ((signed int) calibrationPoints[2].x) - ((signed int) calibrationPoints[3].x);
xSlope = (slope1 + slope2) / 2;
slope1 = ((signed int) calibrationPoints[0].data[1]) - ((signed int) calibrationPoints[2].data[1]);
slope1 *= 1024;
slope1 /= ((signed int) calibrationPoints[0].y) - ((signed int) calibrationPoints[2].y);
slope2 = ((signed int) calibrationPoints[1].data[1]) - ((signed int) calibrationPoints[3].data[1]);
slope2 *= 1024;
slope2 /= ((signed int) calibrationPoints[1].y) - ((signed int) calibrationPoints[3].y);
ySlope = (slope1 + slope2) / 2;
// Test point
LCDD_Fill(pLcdBuffer, 0xFFFFFF);
LCDD_DrawString(pLcdBuffer, 30, 50, "LCD calibration", COLOR_BLACK);
LCDD_DrawString(pLcdBuffer, 1, 100, " Touch the point to\nvalidate calibration", COLOR_DARKBLUE);
DrawCalibrationPoint(pLcdBuffer, &testPoint);
// Wait for touch & end of conversion
TSD_WaitPenPressed();
TSD_GetRawMeasurement(measuredPoint.data);
TSDCom_InterpolateMeasurement(measuredPoint.data, (unsigned int *) &measuredPoint);
DrawCalibrationPoint(pLcdBuffer, &measuredPoint);
// Check resulting x and y
xDiff = (signed int) measuredPoint.x - (signed int) testPoint.x;
yDiff = (signed int) measuredPoint.y - (signed int) testPoint.y;
xOk = (xDiff >= -POINTS_MAX_ERROR) && (xDiff <= POINTS_MAX_ERROR);
yOk = (yDiff >= -POINTS_MAX_ERROR) && (yDiff <= POINTS_MAX_ERROR);
// Wait for contact loss
TSD_WaitPenReleased();
// Check calibration result
if (xOk && yOk) {
bCalibrationOk = 1;
LCDD_Fill(pLcdBuffer, COLOR_WHITE);
LCDD_DrawString(pLcdBuffer, 30, 50, "LCD calibration", COLOR_BLACK);
LCDD_DrawString(pLcdBuffer, 80, 100, "Success !", COLOR_GREEN);
}
else {
bCalibrationOk = 0;
LCDD_Fill(pLcdBuffer, COLOR_WHITE);
LCDD_DrawString(pLcdBuffer, 30, 50, "LCD calibration", COLOR_BLACK);
LCDD_DrawString(pLcdBuffer, 40, 100, "Error too big", COLOR_RED);
}
// Slight delay
for (i = 0; i < DELAY_RESULT_DISPLAY; i++);
#ifdef AT91C_ID_LCDC
// Restore old LCD buffer
LCDD_DisplayBuffer(pOldLcdBuffer);
#endif
return (xOk && yOk);
}
