ugfx/drivers/touchscreen/ADS7843/touchscreen_lld.c

/*
    ChibiOS/GFX - Copyright (C) 2012
                 Joel Bodenmann aka Tectu <joel@unormal.org>

    This file is part of ChibiOS/GFX.

    ChibiOS/GFX is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 3 of the License, or
    (at your option) any later version.

    ChibiOS/GFX is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

/**
 * @file    drivers/touchscreen/ADS7843/touchscreen_lld.c
 * @brief   Touchscreen Driver subsystem low level driver source.
 *
 * @addtogroup TOUCHSCREEN
 * @{
 */

#include "ch.h"
#include "hal.h"
#include "touchscreen.h"

#if GFX_USE_TOUCHSCREEN /*|| defined(__DOXYGEN__)*/

/*===========================================================================*/
/* Driver local definitions.                                                 */
/*===========================================================================*/

/*===========================================================================*/
/* Driver exported variables.                                                */
/*===========================================================================*/

/*===========================================================================*/
/* Driver local variables.                                                   */
/*===========================================================================*/
#if !defined(__DOXYGEN__)
    /* Local copy of the current touchscreen driver */
    static const TouchscreenDriver *tsDriver;

    static uint16_t sampleBuf[7];
#endif

/*===========================================================================*/
/* Driver local functions.                                                   */
/*===========================================================================*/

/*===========================================================================*/
/* Driver interrupt handlers.                                                */
/*===========================================================================*/

/*===========================================================================*/
/* Driver exported functions.                                                */
/*===========================================================================*/

/* ---- Required Routines ---- */

/**
 * @brief   Low level touchscreen driver initialization.
 *
 * @param[in] ts	The touchscreen driver
 *
 * @notapi
 */
void ts_lld_init(const TouchscreenDriver *ts) {
	tsDriver = ts;

	if(tsDriver->direct_init)
		spiStart(tsDriver->spip, tsDriver->spicfg);
}


/**
 * @brief   Reads a conversion from the touchscreen
 *
 * @param[in] cmd    The command bits to send to the touchscreen
 *
 * @return  The read value 12-bit right-justified
 *
 * @note    This function only reads data, it is assumed that the pins are
 *          configured properly and the bus has been acquired beforehand
 *
 * @notapi
 */
uint16_t ts_lld_read_value(uint8_t cmd) {
	static uint8_t txbuf[3] = {0};
	static uint8_t rxbuf[3] = {0};
	uint16_t ret;

	txbuf[0] = cmd;

	spiExchange(tsDriver->spip, 3, txbuf, rxbuf);

	ret = (rxbuf[1] << 5) | (rxbuf[2] >> 3);

	return ret;
}

/**
 * @brief   7-point median filtering code for touchscreen samples
 *
 * @note    This is an internally used routine only.
 *
 * @notapi
 */
static void ts_lld_filter(void) {
	uint16_t temp;
	int i,j;

	for(i = 0; i < 4; i++) {
		for(j = i; j < 7; j++) {
			if(sampleBuf[i] > sampleBuf[j]) {
				/* Swap the values */
				temp = sampleBuf[i];
				sampleBuf[i] = sampleBuf[j];
				sampleBuf[j] = temp;
			}
		}
	}
}

/**
 * @brief   Reads out the X direction.
 *
 * @note    The samples are median filtered for greater noise reduction
 *
 * @notapi
 */
uint16_t ts_lld_read_x(void) {
	int i;

#if defined(SPI_USE_MUTUAL_EXCLUSION)
	spiAcquireBus(tsDriver->spip);
#endif

	TOUCHSCREEN_SPI_PROLOGUE();
	palClearPad(tsDriver->spicfg->ssport, tsDriver->spicfg->sspad);

	/* Discard the first conversion - very noisy and keep the ADC on hereafter
	 * till we are done with the sampling. Note that PENIRQ is disabled.
 	 */
	ts_lld_read_value(0xD1);

	for(i = 0; i < 7; i++) {
		sampleBuf[i] = ts_lld_read_value(0xD1);
	}

	/* Switch on PENIRQ once again - perform a dummy read */
	ts_lld_read_value(0xD0);

	palSetPad(tsDriver->spicfg->ssport, tsDriver->spicfg->sspad);
	TOUCHSCREEN_SPI_EPILOGUE();

#if defined(SPI_USE_MUTUAL_EXCLUSION)
	spiReleaseBus(tsDriver->spip);
#endif

	/* Find the median - use selection sort */
	ts_lld_filter();

	return sampleBuf[3];
}

/*
 * @brief	Reads out the Y direction.
 *
 * @notapi
 */
uint16_t ts_lld_read_y(void) {
	int i;

#if defined(SPI_USE_MUTUAL_EXCLUSION)
	spiAcquireBus(tsDriver->spip);
#endif

	TOUCHSCREEN_SPI_PROLOGUE();
	palClearPad(tsDriver->spicfg->ssport, tsDriver->spicfg->sspad);

	/* Discard the first conversion - very noisy and keep the ADC on hereafter
	 * till we are done with the sampling. Note that PENIRQ is disabled.
	 */
	ts_lld_read_value(0x91);

	for(i = 0; i < 7; i++) {
		sampleBuf[i] = ts_lld_read_value(0x91);
	}

	/* Switch on PENIRQ once again - perform a dummy read */
	ts_lld_read_value(0x90);

	palSetPad(tsDriver->spicfg->ssport, tsDriver->spicfg->sspad);
	TOUCHSCREEN_SPI_EPILOGUE();

#ifdef SPI_USE_MUTUAL_EXCLUSION
	spiReleaseBus(tsDriver->spip);
#endif

	/* Find the median - use selection sort */
	ts_lld_filter();

	return sampleBuf[3];
}

/* ---- Optional Routines ---- */
#if TOUCHSCREEN_HAS_IRQ || defined(__DOXYGEN__)
	/*
	 * @brief	for checking if touchscreen is pressed or not.
	 *
	 * @return	1 if pressed / 0 if not pressed
	 *
	 * @notapi
	 */
	uint8_t ts_lld_pressed(void) {
		return (!palReadPad(tsDriver->tsIRQPort, tsDriver->tsIRQPin));
	}
#endif

#if TOUCHSCREEN_HAS_PRESSURE || defined(__DOXYGEN__)
	/*
	 * @brief	Reads out the Z direction / pressure.
	 *
	 * @notapi
	 */
	uint16_t ts_lld_read_z(void) {
		/* ToDo */
		return 42;
	}
#endif

#endif /* GFX_USE_TOUCHSCREEN */
/** @} */