/****************************************************************************
 * boards/arm/kl/freedom-kl26z/src/kl_tsi.c
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.  The
 * ASF licenses this file to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the
 * License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
 * License for the specific language governing permissions and limitations
 * under the License.
 *
 ****************************************************************************/

/* Reference:
 * https://community.freescale.com/community/
 * the-embedded-beat/blog/2012/10/15/
 * using-the-touch-interface-on-the-freescale-freedom-development-platform
 */

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/config.h>

#include <stdint.h>
#include <errno.h>
#include <debug.h>

#include <nuttx/fs/fs.h>

#include "arm_internal.h"
#include "kl_gpio.h"
#include "hardware/kl_tsi.h"
#include "hardware/kl_pinmux.h"
#include "hardware/kl_sim.h"

#ifdef CONFIG_KL_TSI

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/

/* The touchpad on the Freedom KL26Z board connects to the MCU via:
 *
 *   PTB16 TWI0_CH9
 *   PTB17 TSI0_CH10
 */

#define NSENSORS 2

/****************************************************************************
 * Private Function Prototypes
 ****************************************************************************/

static void    tsi_calibrate(void);
static ssize_t tsi_read(struct file *filep,
                        char *buffer, size_t buflen);

/****************************************************************************
 * Private Data
 ****************************************************************************/

static uint16_t g_defcap[NSENSORS];    /* Default capacitance for each sensor */
static uint16_t g_currdelta = 0;       /* Current delta for the current button */
static uint8_t  g_channel = 0;         /* Current g_channel */

/* Channel assigned to each sensor */

static uint8_t const g_chsensor[NSENSORS] =
{
  9,
  10
};

/* Character driver operations */

static const struct file_operations tsi_ops =
{
  NULL,        /* open */
  NULL,        /* close */
  tsi_read,    /* read */
  NULL,        /* write */
  NULL,        /* seek */
  NULL,        /* ioctl */
  NULL         /* poll */
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
  , NULL       /* unlink */
#endif
};

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Name: tsi_calibrate
 ****************************************************************************/

static void tsi_calibrate(void)
{
  uint32_t regval;
  int i;

  for (i = 0; i < NSENSORS; i++)
    {
      /* Clear end of scan flag */

      regval  = getreg32(KL_TSI_GENCS);
      regval |= TSI_GENCS_EOSF;
      putreg32(regval, KL_TSI_GENCS);

      /* Scan the next electrode */

      regval = TSI_DATA_TSICH(g_chsensor[i]);
      putreg32(regval, KL_TSI_DATA);

      regval |= TSI_DATA_SWTS;
      putreg32(regval, KL_TSI_DATA);

      /* Wait until the conversion is done */

      while (!(getreg32(KL_TSI_GENCS) & TSI_GENCS_EOSF));

      g_defcap[i] = getreg32(KL_TSI_DATA) & TSI_DATA_TSICNT_MASK;
      iinfo("Sensor %d = %d\n", i + 1, g_defcap[i]);
    }
}

/****************************************************************************
 * Name: tsi_read
 ****************************************************************************/

static ssize_t tsi_read(struct file *filep, char *buf, size_t buflen)
{
  static int deltacap = 0;
  uint32_t regval;

  if (buf == NULL || buflen < 1)
    {
      /* Well... nothing to do */

      return -EINVAL;
    }

  deltacap = 0;

  /* Clear end of scan flag */

  regval  = getreg32(KL_TSI_GENCS);
  regval |= TSI_GENCS_EOSF;
  putreg32(regval, KL_TSI_GENCS);

  /* Scan the next electrode */

  regval = TSI_DATA_TSICH(g_chsensor[g_channel]);
  putreg32(regval, KL_TSI_DATA);

  regval |= TSI_DATA_SWTS;
  putreg32(regval, KL_TSI_DATA);

  /* Wait until the conversion is done */

  while (!(getreg32(KL_TSI_GENCS) & TSI_GENCS_EOSF));

  /* Compute delta using calibration reference counts */

  deltacap  = getreg32(KL_TSI_DATA) & TSI_DATA_TSICNT_MASK;
  deltacap -= g_defcap[g_channel];

  if (deltacap < 0)
    {
      deltacap = 0;
    }

  g_currdelta = (uint16_t)deltacap;

  iinfo("Delta for g_channel %d = %d\n", g_channel, g_currdelta);

  buf[0] = g_currdelta & 0xff;
  buf[1] = (g_currdelta & 0xff00) >> 8;
  buf[2] = g_channel;

  /* Increment the channel index to sample the next sensor on the next timer
   * that read() is called.
   */

  g_channel++;
  if (g_channel >= NSENSORS)
    {
      g_channel = 0;
    }

  return 3;
}

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: kl_tsi_initialize
 *
 * Description:
 *   Initialize the TSI hardware and interface for the sliders on board the
 *   Freedom KL26Z board.  Register a character driver at /dev/tsi that may
 *   be used to read from each sensor.
 *
 ****************************************************************************/

void kl_tsi_initialize(void)
{
  uint32_t regval;

  /* Enable access to the TSI module */

  regval = getreg32(KL_SIM_SCGC5);
  regval |= SIM_SCGC5_TSI;
  putreg32(regval, KL_SIM_SCGC5);

  /* Configure PINs used on TSI */

  kl_configgpio(PIN_TSI0_CH9);
  kl_configgpio(PIN_TSI0_CH10);

  /* Configure TSI parameter */

  regval = getreg32(KL_TSI_GENCS);
  regval |= TSI_GENCS_MODE_CAPSENSING | TSI_GENCS_REFCHRG_8UA |
            TSI_GENCS_DVOLT_1p03V | TSI_GENCS_EXTCHRG_64A |
            TSI_GENCS_PS_DIV16 | TSI_GENCS_NSCN_TIMES(12) | TSI_GENCS_STPE;
  putreg32(regval, KL_TSI_GENCS);

  /* Only after setting TSI we should enable it */

  regval  = getreg32(KL_TSI_GENCS);
  regval |= TSI_GENCS_TSIEN;
  putreg32(regval, KL_TSI_GENCS);

  /* Calibrate it before to use */

  tsi_calibrate();

  /* And finally register the TSI character driver */

  register_driver("/dev/tsi", &tsi_ops, 0444, NULL);
}

#endif /* CONFIG_KL_TSI */