ChibiOS/os/hal/platforms/STM32/i2c_lld.c

/*
    ChibiOS/RT - Copyright (C) 2006,2007,2008,2009,2010,
                 2011 Giovanni Di Sirio.

    This file is part of ChibiOS/RT.

    ChibiOS/RT 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/RT 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    STM32/i2c_lld.c
 * @brief   STM32 I2C subsystem low level driver source.
 *
 * @addtogroup I2C
 * @{
 */

#include "ch.h"
#include "hal.h"
#include "i2c_lld.h"

#if HAL_USE_I2C || defined(__DOXYGEN__)

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

#define I2C1_RX_DMA_CHANNEL                                                 \
  STM32_DMA_GETCHANNEL(STM32_I2C_I2C1_RX_DMA_STREAM,                        \
                       STM32_I2C1_RX_DMA_CHN)

#define I2C1_TX_DMA_CHANNEL                                                 \
  STM32_DMA_GETCHANNEL(STM32_I2C_I2C1_TX_DMA_STREAM,                        \
                       STM32_I2C1_TX_DMA_CHN)

#define I2C2_RX_DMA_CHANNEL                                                 \
  STM32_DMA_GETCHANNEL(STM32_I2C_I2C2_RX_DMA_STREAM,                        \
                       STM32_I2C2_RX_DMA_CHN)

#define I2C2_TX_DMA_CHANNEL                                                 \
  STM32_DMA_GETCHANNEL(STM32_I2C_I2C2_TX_DMA_STREAM,                        \
                       STM32_I2C2_TX_DMA_CHN)

#define I2C3_RX_DMA_CHANNEL                                                 \
  STM32_DMA_GETCHANNEL(STM32_I2C_I2C3_RX_DMA_STREAM,                        \
                       STM32_I2C3_RX_DMA_CHN)

#define I2C3_TX_DMA_CHANNEL                                                 \
  STM32_DMA_GETCHANNEL(STM32_I2C_I2C3_TX_DMA_STREAM,                        \
                       STM32_I2C3_TX_DMA_CHN)

/*===========================================================================*/
/* Driver constants.                                                         */
/*===========================================================================*/

#define I2C_EV5_MASTER_MODE_SELECT                                          \
  ((uint32_t)(((I2C_SR2_MSL | I2C_SR2_BUSY) << 16) | I2C_SR1_SB))
#define I2C_EV6_MASTER_TRA_MODE_SELECTED                                    \
  ((uint32_t)(((I2C_SR2_MSL|I2C_SR2_BUSY|I2C_SR2_TRA) << 16) |              \
              I2C_SR1_ADDR|I2C_SR1_TXE))
#define I2C_EV6_MASTER_REC_MODE_SELECTED                                    \
  ((uint32_t)(((I2C_SR2_MSL|I2C_SR2_BUSY)<< 16) | I2C_SR1_ADDR))
#define I2C_EV8_2_MASTER_BYTE_TRANSMITTED                                   \
  ((uint32_t)(((I2C_SR2_MSL | I2C_SR2_BUSY | I2C_SR2_TRA) << 16) |          \
              I2C_SR1_BTF | I2C_SR1_TXE))
#define I2C_EV_MASK 0x00FFFFFF

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

/** @brief I2C1 driver identifier.*/
#if STM32_I2C_USE_I2C1 || defined(__DOXYGEN__)
I2CDriver I2CD1;
#endif

/** @brief I2C2 driver identifier.*/
#if STM32_I2C_USE_I2C2 || defined(__DOXYGEN__)
I2CDriver I2CD2;
#endif

/** @brief I2C3 driver identifier.*/
#if STM32_I2C_USE_I2C3 || defined(__DOXYGEN__)
I2CDriver I2CD3;
#endif

/*===========================================================================*/
/* Driver local variables.                                                   */
/*===========================================================================*/

/* The following variables have debugging purpose only and are included when
   the option CH_DBG_ENABLE_ASSERTS is enabled.*/
#if CH_DBG_ENABLE_ASSERTS
static volatile uint16_t dbgSR1;
static volatile uint16_t dbgSR2;
static volatile uint16_t dbgCR1;
static volatile uint16_t dbgCR2;
#endif /* CH_DBG_ENABLE_ASSERTS */

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

/**
 * @brief   Set clock speed.
 *
 * @param[in] i2cp      pointer to the @p I2CDriver object
 *
 * @notapi
 */
static void i2c_lld_set_clock(I2CDriver *i2cp) {
  uint16_t regCCR, clock_div;
  int32_t clock_speed = i2cp->config->clock_speed;
  i2cdutycycle_t duty = i2cp->config->duty_cycle;

  chDbgCheck((i2cp != NULL) && (clock_speed > 0) && (clock_speed <= 4000000),
             "i2c_lld_set_clock");

  /* CR2 Configuration.*/
  i2cp->i2c->CR2 &= (uint16_t)~I2C_CR2_FREQ;
  i2cp->i2c->CR2 |= (uint16_t)I2C_CLK_FREQ;

  /* CCR Configuration.*/
  regCCR = 0;                                                   /* Clear F/S, DUTY and CCR[11:0] bits */
  clock_div = I2C_CCR_CCR;

  if (clock_speed <= 100000) {                                  /* Configure clock_div in standard mode */

    chDbgAssert(duty == STD_DUTY_CYCLE,
                "i2c_lld_set_clock(), #1",
                "Invalid standard mode duty cycle");

    clock_div = (uint16_t)(STM32_PCLK1 / (clock_speed * 2));    /* Standard mode clock_div calculate: Tlow/Thigh = 1/1 */
    if (clock_div < 0x04) clock_div = 0x04;                     /* Test if CCR value is under 0x4, and set the minimum allowed value */
    regCCR |= (clock_div & I2C_CCR_CCR);                        /* Set clock_div value for standard mode */
    i2cp->i2c->TRISE = I2C_CLK_FREQ + 1;                             /* Set Maximum Rise Time for standard mode */
  }
  else if (clock_speed <= 400000) {                              /* Configure clock_div in fast mode */

    chDbgAssert((duty == FAST_DUTY_CYCLE_2) || (duty == FAST_DUTY_CYCLE_16_9),
                "i2c_lld_set_clock(), #2",
                "Invalid fast mode duty cycle");

    if (duty == FAST_DUTY_CYCLE_2) {
      /* Fast mode clock_div calculate: Tlow/Thigh = 2/1.*/
      clock_div = (uint16_t)(STM32_PCLK1 / (clock_speed * 3));
    }
    else if (duty == FAST_DUTY_CYCLE_16_9) {
      /* Fast mode clock_div calculate: Tlow/Thigh = 16/9.*/
      clock_div = (uint16_t)(STM32_PCLK1 / (clock_speed * 25));
      regCCR |= I2C_CCR_DUTY;
    }
    if (clock_div < 0x01) clock_div = 0x01;                      /* Test if CCR value is under 0x1, and set the minimum allowed value */
    regCCR |= (I2C_CCR_FS | (clock_div & I2C_CCR_CCR));         /* Set clock_div value and F/S bit for fast mode*/
    i2cp->i2c->TRISE = (I2C_CLK_FREQ * 300 / 1000) + 1;              /* Set Maximum Rise Time for fast mode */
  }
  chDbgAssert((clock_div <= I2C_CCR_CCR),
      "i2c_lld_set_clock(), #3", "Too low clock clock speed selected");

  i2cp->i2c->CCR = regCCR;
}

/**
 * @brief   Set operation mode of I2C hardware.
 *
 * @param[in] i2cp      pointer to the @p I2CDriver object
 *
 * @notapi
 */
static void i2c_lld_set_opmode(I2CDriver *i2cp) {
  i2copmode_t opmode = i2cp->config->op_mode;
  uint16_t regCR1;

  regCR1 = i2cp->i2c->CR1;
  switch (opmode) {
  case OPMODE_I2C:
    regCR1 &= (uint16_t)~(I2C_CR1_SMBUS|I2C_CR1_SMBTYPE);
    break;
  case OPMODE_SMBUS_DEVICE:
    regCR1 |= I2C_CR1_SMBUS;
    regCR1 &= (uint16_t)~(I2C_CR1_SMBTYPE);
    break;
  case OPMODE_SMBUS_HOST:
    regCR1 |= (I2C_CR1_SMBUS|I2C_CR1_SMBTYPE);
    break;
  }

  i2cp->i2c->CR1 = regCR1;
}


/**
 * @brief   Receive data via the I2C bus after writing.
 *
 * @param[in] i2cp        pointer to the @p I2CDriver object
 *
 * @notapi
 */
static void i2c_lld_master_transceive(I2CDriver *i2cp) {

  /* init driver fields */
  i2cp->addr |= 0x01;    /* LSB = 1 -> receive */

  /* TODO: DMA error handling */
  dmaStreamSetMemory0(i2cp->dmarx, i2cp->rxbuf);
  dmaStreamSetTransactionSize(i2cp->dmarx, i2cp->rxbytes);
  dmaStreamSetMode(i2cp->dmarx, ((i2cp->dmamode) | STM32_DMA_CR_DIR_P2M));

  i2cp->i2c->CR1 |= I2C_CR1_START | I2C_CR1_ACK;
}


/**
 * @brief   Return the last event value from I2C status registers.
 * @details Important but implicit destination of this function is
 *          clearing interrupts flags.
 * @note    Internal use only.
 *
 * @param[in] i2cp      pointer to the @p I2CDriver object
 *
 * @notapi
 */
static uint32_t i2c_get_event(I2CDriver *i2cp) {
  uint16_t regSR1 = i2cp->i2c->SR1;
  uint16_t regSR2 = i2cp->i2c->SR2;

#if CH_DBG_ENABLE_ASSERTS
    dbgSR1 = regSR1;
    dbgSR2 = regSR2;
    dbgCR1 = i2cp->i2c->CR1;
    dbgCR2 = i2cp->i2c->CR2;
#endif /* CH_DBG_ENABLE_ASSERTS */

  return (I2C_EV_MASK & (regSR1 | (regSR2 << 16)));
}


/**
 * @brief   I2C shared ISR code.
 *
 * @param[in] i2cp      pointer to the @p I2CDriver object
 *
 * @notapi
 */
static void i2c_serve_event_interrupt(I2CDriver *i2cp) {
  I2C_TypeDef *dp = i2cp->i2c;

  switch (i2c_get_event(i2cp)) {
  case I2C_EV5_MASTER_MODE_SELECT:
    dp->DR = i2cp->addr;
    break;
  case I2C_EV6_MASTER_REC_MODE_SELECTED:
    dmaStreamEnable(i2cp->dmarx);
    i2cp->i2c->CR2 |= I2C_CR2_DMAEN | I2C_CR2_LAST;
    break;
  case I2C_EV6_MASTER_TRA_MODE_SELECTED:
    dmaStreamEnable(i2cp->dmatx);
    i2cp->i2c->CR2 |= I2C_CR2_DMAEN | I2C_CR2_LAST;
    break;
  case I2C_EV8_2_MASTER_BYTE_TRANSMITTED:
    /* Catches BTF event after the end of transmission.*/
    if (i2cp->rxbytes > 1) {
      /* Starts "read after write" operation.*/
      i2c_lld_master_transceive(i2cp);
      return;
    }
    else
      i2cp->i2c->CR1 |= I2C_CR1_STOP;
      i2c_lld_isr_code(i2cp);
    break;
  default:
    break;
  }
}

/**
 * @brief   DMA RX end IRQ handler.
 *
 * @param[in] i2cp      pointer to the @p I2CDriver object
 *
 * @notapi
 */
static void i2c_lld_serve_rx_end_irq(I2CDriver *i2cp) {

  dmaStreamDisable(i2cp->dmarx);
  i2cp->i2c->CR1 |= I2C_CR1_STOP;
  i2c_lld_isr_code(i2cp);
}

/**
 * @brief    DMA TX end IRQ handler.
 *
 * @param[in] i2cp      pointer to the @p I2CDriver object
 *
 * @notapi
 */
static void i2c_lld_serve_tx_end_irq(I2CDriver *i2cp) {

  dmaStreamDisable(i2cp->dmatx);
}

/**
 * @brief   I2C error handler.
 *
 * @param[in] i2cp      pointer to the @p I2CDriver object
 *
 * @notapi
 */
static void i2c_serve_error_interrupt(I2CDriver *i2cp) {
  i2cflags_t errors;

  chSysLockFromIsr();
  /* Clears interrupt flags just to be safe.*/
  dmaStreamDisable(i2cp->dmatx);
  dmaStreamDisable(i2cp->dmarx);
  dmaStreamClearInterrupt(i2cp->dmatx);
  dmaStreamClearInterrupt(i2cp->dmarx);
  chSysUnlockFromIsr();

  errors = I2CD_NO_ERROR;

  if (i2cp->i2c->SR1 & I2C_SR1_BERR) {              /* Bus error.           */
    i2cp->i2c->SR1 &= ~I2C_SR1_BERR;
    errors |= I2CD_BUS_ERROR;
  }
  if (i2cp->i2c->SR1 & I2C_SR1_ARLO) {              /* Arbitration lost.    */
    i2cp->i2c->SR1 &= ~I2C_SR1_ARLO;
    errors |= I2CD_ARBITRATION_LOST;
  }
  if (i2cp->i2c->SR1 & I2C_SR1_AF) {                /* Acknowledge fail.    */
    i2cp->i2c->SR1 &= ~I2C_SR1_AF;
    i2cp->i2c->CR1 |= I2C_CR1_STOP;                 /* Setting stop bit.    */
    errors |= I2CD_ACK_FAILURE;
  }
  if (i2cp->i2c->SR1 & I2C_SR1_OVR) {               /* Overrun.             */
    i2cp->i2c->SR1 &= ~I2C_SR1_OVR;
    errors |= I2CD_OVERRUN;
  }
  if (i2cp->i2c->SR1 & I2C_SR1_PECERR) {            /* PEC error.           */
    i2cp->i2c->SR1 &= ~I2C_SR1_PECERR;
    errors |= I2CD_PEC_ERROR;
  }
  if (i2cp->i2c->SR1 & I2C_SR1_TIMEOUT) {           /* SMBus Timeout.       */
    i2cp->i2c->SR1 &= ~I2C_SR1_TIMEOUT;
    errors |= I2CD_TIMEOUT;
  }
  if (i2cp->i2c->SR1 & I2C_SR1_SMBALERT) {          /* SMBus alert.         */
    i2cp->i2c->SR1 &= ~I2C_SR1_SMBALERT;
    errors |= I2CD_SMB_ALERT;
  }

  /* If some error has been identified then sends wakes the waitingthread.*/
  if (errors != I2CD_NO_ERROR) {
    i2cp->errors |= errors;
    i2c_lld_isr_err_code(i2cp);
  }
}

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

#if STM32_I2C_USE_I2C1 || defined(__DOXYGEN__)
/**
 * @brief   I2C1 event interrupt handler.
 *
 * @notapi
 */
CH_IRQ_HANDLER(I2C1_EV_IRQHandler) {

  CH_IRQ_PROLOGUE();

  i2c_serve_event_interrupt(&I2CD1);

  CH_IRQ_EPILOGUE();
}

/**
 * @brief   I2C1 error interrupt handler.
 */
CH_IRQ_HANDLER(I2C1_ER_IRQHandler) {

  CH_IRQ_PROLOGUE();

  i2c_serve_error_interrupt(&I2CD1);

  CH_IRQ_EPILOGUE();
}
#endif /* STM32_I2C_USE_I2C1 */

#if STM32_I2C_USE_I2C2 || defined(__DOXYGEN__)
/**
 * @brief   I2C2 event interrupt handler.
 */
CH_IRQ_HANDLER(I2C2_EV_IRQHandler) {

  CH_IRQ_PROLOGUE();

  i2c_serve_event_interrupt(&I2CD2);

  CH_IRQ_EPILOGUE();
}

/**
 * @brief   I2C2 error interrupt handler.
 */
CH_IRQ_HANDLER(I2C2_ER_IRQHandler) {

  CH_IRQ_PROLOGUE();

  i2c_serve_error_interrupt(&I2CD2);

  CH_IRQ_EPILOGUE();
}
#endif /* STM32_I2C_USE_I2C2 */

#if STM32_I2C_USE_I2C3 || defined(__DOXYGEN__)
/**
 * @brief   I2C3 event interrupt handler.
 */
CH_IRQ_HANDLER(I2C3_EV_IRQHandler) {

  CH_IRQ_PROLOGUE();

  i2c_serve_event_interrupt(&I2CD3);

  CH_IRQ_EPILOGUE();
}

/**
 * @brief   I2C3 error interrupt handler.
 */
CH_IRQ_HANDLER(I2C3_ER_IRQHandler) {

  CH_IRQ_PROLOGUE();

  i2c_serve_error_interrupt(&I2CD3);

  CH_IRQ_EPILOGUE();
}
#endif /* STM32_I2C_USE_I2C3 */


/**
 * @brief   Low level I2C driver initialization.
 *
 * @notapi
 */
void i2c_lld_init(void) {

#if STM32_I2C_USE_I2C1
  i2cObjectInit(&I2CD1);
  I2CD1.i2c = I2C1;
  I2CD1.dmarx  = STM32_DMA_STREAM(STM32_I2C_I2C1_RX_DMA_STREAM);
  I2CD1.dmatx  = STM32_DMA_STREAM(STM32_I2C_I2C1_TX_DMA_STREAM);
#endif /* STM32_I2C_USE_I2C1 */

#if STM32_I2C_USE_I2C2
  i2cObjectInit(&I2CD2);
  I2CD2.i2c = I2C2;
  I2CD2.dmarx  = STM32_DMA_STREAM(STM32_I2C_I2C2_RX_DMA_STREAM);
  I2CD2.dmatx  = STM32_DMA_STREAM(STM32_I2C_I2C2_TX_DMA_STREAM);
#endif /* STM32_I2C_USE_I2C2 */

#if STM32_I2C_USE_I2C3
  i2cObjectInit(&I2CD3);
  I2CD3.i2c = I2C3;
  I2CD3.dmarx  = STM32_DMA_STREAM(STM32_I2C_I2C3_RX_DMA_STREAM);
  I2CD3.dmatx  = STM32_DMA_STREAM(STM32_I2C_I2C3_TX_DMA_STREAM);
#endif /* STM32_I2C_USE_I2C3 */
}

/**
 * @brief   Configures and activates the I2C peripheral.
 *
 * @param[in] i2cp      pointer to the @p I2CDriver object
 *
 * @notapi
 */
void i2c_lld_start(I2CDriver *i2cp) {

  i2cp->dmamode = STM32_DMA_CR_PSIZE_BYTE | STM32_DMA_CR_MSIZE_BYTE |
                  STM32_DMA_CR_MINC | STM32_DMA_CR_DMEIE | STM32_DMA_CR_TEIE |
                  STM32_DMA_CR_TCIE;

  /* If in stopped state then enables the I2C and DMA clocks.*/
  if (i2cp->state == I2C_STOP) {

  i2c_lld_reset(i2cp);

#if STM32_I2C_USE_I2C1
    if (&I2CD1 == i2cp) {
      bool_t b;

      b = dmaStreamAllocate(i2cp->dmarx,
                            STM32_I2C_I2C1_IRQ_PRIORITY,
                            (stm32_dmaisr_t)i2c_lld_serve_rx_end_irq,
                            (void *)i2cp);
      chDbgAssert(!b, "i2c_lld_start(), #1", "stream already allocated");
      b = dmaStreamAllocate(i2cp->dmatx,
                            STM32_I2C_I2C1_IRQ_PRIORITY,
                            (stm32_dmaisr_t)i2c_lld_serve_tx_end_irq,
                            (void *)i2cp);
      chDbgAssert(!b, "i2c_lld_start(), #2", "stream already allocated");
      rccEnableI2C1(FALSE);
      nvicEnableVector(I2C1_EV_IRQn,
          CORTEX_PRIORITY_MASK(STM32_I2C_I2C1_IRQ_PRIORITY));
      nvicEnableVector(I2C1_ER_IRQn,
          CORTEX_PRIORITY_MASK(STM32_I2C_I2C1_IRQ_PRIORITY));

      i2cp->dmamode |= STM32_DMA_CR_CHSEL(I2C1_RX_DMA_CHANNEL) |
                       STM32_DMA_CR_PL(STM32_I2C_I2C1_DMA_PRIORITY);
    }
#endif /* STM32_I2C_USE_I2C1 */

#if STM32_I2C_USE_I2C2
    if (&I2CD2 == i2cp) {
      bool_t b;

      b = dmaStreamAllocate(i2cp->dmarx,
                            STM32_I2C_I2C2_IRQ_PRIORITY,
                            (stm32_dmaisr_t)i2c_lld_serve_rx_end_irq,
                            (void *)i2cp);
      chDbgAssert(!b, "i2c_lld_start(), #3", "stream already allocated");
      b = dmaStreamAllocate(i2cp->dmatx,
                            STM32_I2C_I2C2_IRQ_PRIORITY,
                            (stm32_dmaisr_t)i2c_lld_serve_tx_end_irq,
                            (void *)i2cp);
      chDbgAssert(!b, "i2c_lld_start(), #4", "stream already allocated");
      rccEnableI2C2(FALSE);
      nvicEnableVector(I2C2_EV_IRQn,
          CORTEX_PRIORITY_MASK(STM32_I2C_I2C2_IRQ_PRIORITY));
      nvicEnableVector(I2C2_ER_IRQn,
          CORTEX_PRIORITY_MASK(STM32_I2C_I2C2_IRQ_PRIORITY));

      i2cp->dmamode |= STM32_DMA_CR_CHSEL(I2C2_RX_DMA_CHANNEL) |
                       STM32_DMA_CR_PL(STM32_I2C_I2C2_DMA_PRIORITY);
    }
#endif /* STM32_I2C_USE_I2C2 */

#if STM32_I2C_USE_I2C3
    if (&I2CD3 == i2cp) {
      bool_t b;

      b = dmaStreamAllocate(i2cp->dmarx,
                            STM32_I2C_I2C3_IRQ_PRIORITY,
                            (stm32_dmaisr_t)i2c_lld_serve_rx_end_irq,
                            (void *)i2cp);
      chDbgAssert(!b, "i2c_lld_start(), #5", "stream already allocated");
      b = dmaStreamAllocate(i2cp->dmatx,
                            STM32_I2C_I2C3_IRQ_PRIORITY,
                            (stm32_dmaisr_t)i2c_lld_serve_tx_end_irq,
                            (void *)i2cp);
      chDbgAssert(!b, "i2c_lld_start(), #6", "stream already allocated");
      rccEnableI2C3(FALSE);
      nvicEnableVector(I2C3_EV_IRQn,
          CORTEX_PRIORITY_MASK(STM32_I2C_I2C3_IRQ_PRIORITY));
      nvicEnableVector(I2C3_ER_IRQn,
          CORTEX_PRIORITY_MASK(STM32_I2C_I2C3_IRQ_PRIORITY));

      i2cp->dmamode |= STM32_DMA_CR_CHSEL(I2C3_RX_DMA_CHANNEL) |
                       STM32_DMA_CR_PL(STM32_I2C_I2C3_DMA_PRIORITY);
    }
#endif /* STM32_I2C_USE_I2C3 */
  }

  /* I2C registers pointed by the DMA.*/
  dmaStreamSetPeripheral(i2cp->dmarx, &i2cp->i2c->DR);
  dmaStreamSetPeripheral(i2cp->dmatx, &i2cp->i2c->DR);

  /* Reset i2c peripheral.*/
  i2cp->i2c->CR1 = I2C_CR1_SWRST;
  i2cp->i2c->CR1 = 0;

  /* Setup I2C parameters.*/
  i2c_lld_set_clock(i2cp);
  i2c_lld_set_opmode(i2cp);

  /* Ready to go.*/
  i2cp->i2c->CR1 |= I2C_CR1_PE;
}

/**
 * @brief   Deactivates the I2C peripheral.
 *
 * @param[in] i2cp      pointer to the @p I2CDriver object
 *
 * @notapi
 */
void i2c_lld_stop(I2CDriver *i2cp) {

  /* If not in stopped state then disables the I2C clock.*/
  if (i2cp->state != I2C_STOP) {

    i2c_lld_reset(i2cp);

    dmaStreamDisable(i2cp->dmatx);
    dmaStreamDisable(i2cp->dmarx);
    dmaStreamClearInterrupt(i2cp->dmatx);
    dmaStreamClearInterrupt(i2cp->dmarx);
    dmaStreamRelease(i2cp->dmatx);
    dmaStreamRelease(i2cp->dmarx);

#if STM32_I2C_USE_I2C1
    if (&I2CD1 == i2cp) {
      nvicDisableVector(I2C1_EV_IRQn);
      nvicDisableVector(I2C1_ER_IRQn);
      rccDisableI2C1(FALSE);
    }
#endif

#if STM32_I2C_USE_I2C2
    if (&I2CD2 == i2cp) {
      nvicDisableVector(I2C2_EV_IRQn);
      nvicDisableVector(I2C2_ER_IRQn);
      rccDisableI2C2(FALSE);
    }
#endif

#if STM32_I2C_USE_I2C3
    if (&I2CD3 == i2cp) {
      nvicDisableVector(I2C3_EV_IRQn);
      nvicDisableVector(I2C3_ER_IRQn);
      rccDisableI2C3(FALSE);
    }
#endif
  }
}

/**
 * @brief   Resets the interface via RCC.
 *
 * @param[in] i2cp      pointer to the @p I2CDriver object
 *
 * @notapi
 */
void i2c_lld_reset(I2CDriver *i2cp) {
  chDbgCheck((i2cp->state == I2C_STOP)||(i2cp->state == I2C_READY),
             "i2c_lld_reset: invalid state");

#if STM32_I2C_USE_I2C1
  if (&I2CD1 == i2cp)
    rccResetI2C1();
#endif /* STM32_I2C_USE_I2C1 */

#if STM32_I2C_USE_I2C2
  if (&I2CD2 == i2cp)
    rccResetI2C2();
#endif /* STM32_I2C_USE_I2C2 */

#if STM32_I2C_USE_I2C3
  if (&I2CD3 == i2cp)
      rccResetI2C3();
#endif /* STM32_I2C_USE_I2C3 */
}

/**
 * @brief   Receives data via the I2C bus as master.
 * @details Number of receiving bytes must be more than 1 because of stm32
 *          hardware restrictions.
 *
 * @param[in] i2cp      pointer to the @p I2CDriver object
 * @param[in] addr      slave device address
 * @param[out] rxbuf    pointer to the receive buffer
 * @param[in] rxbytes   number of bytes to be received
 * @param[in] timeout   the number of ticks before the operation timeouts,
 *                      the following special values are allowed:
 *                      - @a TIME_INFINITE no timeout.
 *                      .
 * @return              The operation status.
 * @retval RDY_OK       if the function succeeded.
 * @retval RDY_RESET    if one or more I2C errors occurred, the errors can
 *                      be retrieved using @p i2cGetErrors().
 * @retval RDY_TIMEOUT  if a timeout occurred before operation end.
 *
 * @notapi
 */
msg_t i2c_lld_master_receive_timeout(I2CDriver *i2cp, i2caddr_t addr,
                                     uint8_t *rxbuf, size_t rxbytes,
                                     systime_t timeout) {
  msg_t rdymsg;

  /* Releases the lock from high level driver.*/
  chSysUnlock();

  chDbgCheck((rxbytes > 1), "i2c_lld_master_receive");

  /* Initializes driver fields, LSB = 1 -> receive.*/
  i2cp->addr = (addr << 1) | 0x01;
  i2cp->rxbytes = rxbytes;
  i2cp->rxbuf = rxbuf;
  i2cp->errors = 0;

  /* TODO: DMA error handling */
  dmaStreamSetMemory0(i2cp->dmarx, rxbuf);
  dmaStreamSetTransactionSize(i2cp->dmarx, rxbytes);
  dmaStreamSetMode(i2cp->dmarx, ((i2cp->dmamode) | STM32_DMA_CR_DIR_P2M));

  /* Waits until BUSY flag is reset.*/
  volatile uint32_t tmo = 1 + (STM32_SYSCLK / 1000000) * 20;
  while((i2cp->i2c->SR2 & I2C_SR2_BUSY) && tmo)
    tmo--;
  if (tmo == 0)
    return RDY_RESET;

  /* wait stop bit from previous transaction*/
  tmo = 1 + (STM32_SYSCLK / 1000000) * 20;
  while((i2cp->i2c->CR1 & I2C_CR1_STOP) && tmo)
    tmo--;
  if (tmo == 0)
    return RDY_RESET;

  /* This lock will be released in high level driver.*/
  chSysLock();

  /* Within the critical zone in order to avoid race conditions.*/
  i2cp->i2c->CR2 |= I2C_CR2_ITERREN | I2C_CR2_ITEVTEN;
  i2cp->i2c->CR1 |= I2C_CR1_START | I2C_CR1_ACK;

  /* Waits for the operation completion.*/
  i2c_lld_wait_s(i2cp, timeout, rdymsg);

  return rdymsg;
}

/**
 * @brief   Transmits data via the I2C bus as master.
 * @details Number of receiving bytes must be 0 or more than 1 because of stm32
 *          hardware restrictions.
 *
 * @param[in] i2cp      pointer to the @p I2CDriver object
 * @param[in] addr      slave device address
 * @param[in] txbuf     pointer to the transmit buffer
 * @param[in] txbytes   number of bytes to be transmitted
 * @param[out] rxbuf    pointer to the receive buffer
 * @param[in] rxbytes   number of bytes to be received
 * @param[in] timeout   the number of ticks before the operation timeouts,
 *                      the following special values are allowed:
 *                      - @a TIME_INFINITE no timeout.
 *                      .
 * @return              The operation status.
 * @retval RDY_OK       if the function succeeded.
 * @retval RDY_RESET    if one or more I2C errors occurred, the errors can
 *                      be retrieved using @p i2cGetErrors().
 * @retval RDY_TIMEOUT  if a timeout occurred before operation end.
 *
 * @notapi
 */
msg_t i2c_lld_master_transmit_timeout(I2CDriver *i2cp, i2caddr_t addr,
                                      const uint8_t *txbuf, size_t txbytes,
                                      uint8_t *rxbuf, size_t rxbytes,
                                      systime_t timeout) {
  msg_t rdymsg;

  /* Releases the lock from high level driver.*/
  chSysUnlock();

  chDbgCheck(((rxbytes == 0) || ((rxbytes > 1) && (rxbuf != NULL))),
      "i2cMasterTransmit");

  /* Initializes driver fields, LSB = 0 -> write.*/
  i2cp->addr = (addr << 1) & 0x00FE;
  i2cp->rxbytes = rxbytes;
  i2cp->rxbuf = rxbuf;
  i2cp->errors = 0;

  /* TODO: DMA error handling */
  dmaStreamSetMemory0(i2cp->dmatx, txbuf);
  dmaStreamSetTransactionSize(i2cp->dmatx, txbytes);
  dmaStreamSetMode(i2cp->dmatx, ((i2cp->dmamode) | STM32_DMA_CR_DIR_M2P));

  /* Waits until BUSY flag is reset.*/
  volatile uint32_t tmo = 1 + (STM32_SYSCLK / 1000000) * 20;
  while((i2cp->i2c->SR2 & I2C_SR2_BUSY) && tmo)
    tmo--;
  if (tmo == 0)
    return RDY_RESET;

  /* Wait stop bit from previous transaction.*/
  tmo = 1 + (STM32_SYSCLK / 1000000) * 20;
  while((i2cp->i2c->CR1 & I2C_CR1_STOP) && tmo)
    tmo--;
  if (tmo == 0)
    return RDY_RESET;

  /* This lock will be released in high level driver.*/
  chSysLock();

  /* Within the critical zone in order to avoid race conditions.*/
  i2cp->i2c->CR2 |= I2C_CR2_ITERREN | I2C_CR2_ITEVTEN;
  i2cp->i2c->CR1 |= I2C_CR1_START;

  /* Waits for the operation completion.*/
  i2c_lld_wait_s(i2cp, timeout, rdymsg);

  return rdymsg;
}

#endif /* HAL_USE_I2C */

/** @} */