drivers/sensors/mcp9844.c

/****************************************************************************
 * drivers/sensors/mcp9844.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.
 *
 ****************************************************************************/

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

#include <nuttx/config.h>

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

#include <nuttx/kmalloc.h>
#include <nuttx/fs/fs.h>
#include <nuttx/i2c/i2c_master.h>
#include <nuttx/sensors/mcp9844.h>
#include <nuttx/random.h>

#if defined(CONFIG_I2C) && defined(CONFIG_SENSORS_MCP9844)

/****************************************************************************
 * Pre-process Definitions
 ****************************************************************************/

#ifndef CONFIG_MCP9844_I2C_FREQUENCY
#  define CONFIG_MCP9844_I2C_FREQUENCY 400000
#endif

/****************************************************************************
 * Private Types
 ****************************************************************************/

struct mcp9844_dev_s
{
  FAR struct i2c_master_s *i2c; /* I2C interface */
  uint8_t addr;                 /* I2C address */
};

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

/* I2C helper functions */

static int     mcp9844_read_u16(FAR struct mcp9844_dev_s *priv,
                                uint8_t const regaddr, FAR uint16_t *value);
static int     mcp9844_write_u16(FAR struct mcp9844_dev_s *priv,
                                 uint8_t const regaddr,
                                 uint16_t const regval);

/* Character driver methods */

static ssize_t mcp9844_read(FAR struct file *filep, FAR char *buffer,
                  size_t buflen);
static ssize_t mcp9844_write(FAR struct file *filep, FAR const char *buffer,
                  size_t buflen);
static int     mcp9844_ioctl(FAR struct file *filep, int cmd,
                  unsigned long arg);

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

static const struct file_operations g_mcp9844_fops =
{
  NULL,            /* open */
  NULL,            /* close */
  mcp9844_read,    /* read */
  mcp9844_write,   /* write */
  NULL,            /* seek */
  mcp9844_ioctl,   /* ioctl */
};

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

/****************************************************************************
 * Name: mcp9844_read_u16
 *
 * Description:
 *  Read a 16 bit valie from the MCP9844 at the address regaddr.
 *
 ****************************************************************************/

static int mcp9844_read_u16(FAR struct mcp9844_dev_s *priv,
                            uint8_t const regaddr, FAR uint16_t *value)
{
  struct i2c_config_s config;
  uint8_t buffer[2];
  int ret = -1;

  /* Set up the I2C configuration */

  config.frequency = CONFIG_MCP9844_I2C_FREQUENCY;
  config.address   = priv->addr;
  config.addrlen   = 7;

  /* Write the register address */

  ret = i2c_write(priv->i2c, &config, &regaddr, 1);
  if (ret < 0)
    {
      snerr ("i2c_write failed: %d\n", ret);
      return ret;
    }

  /* Restart and read 16-bits from the register */

  ret = i2c_read(priv->i2c, &config, buffer, 2);
  if (ret < 0)
    {
      snerr ("i2c_read failed: %d\n", ret);
      return ret;
    }

  /* Copy the content of the buffer to the location of the uint16_t pointer */

  *value = (((uint16_t)(buffer[0])) << 8) + ((uint16_t)(buffer[1]));

  sninfo("addr: %02x value: %08x ret: %d\n", regaddr, *value, ret);
  return OK;
}

/****************************************************************************
 * Name: mcp9844_write_u16
 *
 * Description:
 *   Write to a 16-bit register of the MCP9844.
 *
 ****************************************************************************/

static int mcp9844_write_u16(FAR struct mcp9844_dev_s *priv,
                             uint8_t const regaddr, uint16_t const regval)
{
  struct i2c_config_s config;

  sninfo("addr: %02x value: %08x\n", regaddr, regval);

  /* Set up a 3 byte message to send */

  uint8_t const BUFFER_SIZE = 3;
  uint8_t buffer[BUFFER_SIZE];

  buffer[0] = regaddr;
  buffer[1] = (uint8_t)(regval >> 8);
  buffer[2] = (uint8_t)(regval);

  /* Set up the I2C configuration */

  config.frequency = CONFIG_MCP9844_I2C_FREQUENCY;
  config.address   = priv->addr;
  config.addrlen   = 7;

  /* Write the register address followed by the data (no RESTART) */

  return i2c_write(priv->i2c, &config, buffer, BUFFER_SIZE);
}

/****************************************************************************
 * Name: mcp9844_read
 ****************************************************************************/

static ssize_t mcp9844_read(FAR struct file *filep, FAR char *buffer,
                            size_t buflen)
{
  return -ENOSYS;
}

/****************************************************************************
 * Name: mcp9844_write
 ****************************************************************************/

static ssize_t mcp9844_write(FAR struct file *filep, FAR const char *buffer,
                             size_t buflen)
{
  return -ENOSYS;
}

/****************************************************************************
 * Name: lm75_ioctl
 ****************************************************************************/

static int mcp9844_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
{
  FAR struct inode *inode = filep->f_inode;
  FAR struct mcp9844_dev_s *priv = inode->i_private;
  int ret = OK;

  switch (cmd)
    {
      /* Read from the ambient temperature register. Arg: uint16_t* pointer */

      case SNIOC_READTEMP:
        {
          FAR struct mcp9844_temp_arg_s *temp_result =
            (FAR struct mcp9844_temp_arg_s *)((uintptr_t)arg);

          DEBUGASSERT(temp_result != NULL);

          /* Read the ambient temperature value from the device */

          uint16_t raw_temperature = 0;
          ret = mcp9844_read_u16(priv, MCP9844_TEMP_REG, &raw_temperature);

          /* Convert from the proprietary sensor temperature data
           * representation to a more user-friendly version.
           */

          if (ret == OK)
            {
              /* Feed sensor data to entropy pool */

              add_sensor_randomness(raw_temperature);

              /* BIT15 - 13 contain information if preset temperature values
               * have been exceeded or undercut. BIT12 is now not any longer
               * needed since we do have the sign information retrieved.
               * We do not need them for the temperature so those bits
               * need to be masked out.
               */

              raw_temperature &= 0x0fff; /* 0x0fff = 0b 0000 1111 1111 1111 */

              /* The post comma temperature value is encoded in BIT3 to
               * BIT0
               */

              temp_result->temp_post_comma =
                                  (uint8_t)(raw_temperature & 0x000f);

              /* The pre comma temperature value is encoded in BIT11 to
               * BIT4
               */

              temp_result->temp_pre_comma = (int8_t)(raw_temperature >> 4);
            }
          else
            {
              snerr("ERROR: ioctl::SNIOC_READTEMP - mcp9844_read_u16 failed"
                    " - no temperature retrieved\n");
            }
        }
        break;

      case SNIOC_SETRESOLUTION:
        {
          ret = mcp9844_write_u16(priv, MCP9844_RESO_REG, (uint16_t)(arg));
          if (ret != OK)
            {
              snerr("ERROR: ioctl::SNIOC_SETRESOLUTION - mcp9844_write_u16"
                  "failed - no resolution set\n");
            }
        }
        break;

      case SNIOC_SHUTDOWN:
        {
          uint16_t config_reg;

          /* Perform a read-modify-write cycle on the config register */

          ret = mcp9844_read_u16(priv, MCP9844_CONF_REG, &config_reg);
          if (ret == OK)
            {
              config_reg |= MCP9844_CONF_REG_SHDN;
              ret = mcp9844_write_u16(priv, MCP9844_CONF_REG, config_reg);
              if (ret != OK)
                {
                  snerr("ERROR: ioctl::SNIOC_SHUTDOWN - "
                        "mcp9844_write_u16 failed\n");
                }
            }
          else
            {
              snerr("ERROR: ioctl::SNIOC_SHUTDOWN - "
                    "mcp9844_read_u16 failed\n");
            }
        }
        break;

      case SNIOC_POWERUP:
        {
          uint16_t config_reg;

          /* Perform a read-modify-write cycle on the config register */

          ret = mcp9844_read_u16(priv, MCP9844_CONF_REG, &config_reg);
          if (ret == OK)
            {
              config_reg &= ~MCP9844_CONF_REG_SHDN;
              ret = mcp9844_write_u16(priv, MCP9844_CONF_REG, config_reg);
              if (ret != OK)
                {
                  snerr("ERROR: ioctl::SNIOC_POWERUP - "
                        "mcp9844_write_u16 failed\n");
                }
            }
          else
            {
              snerr("ERROR: ioctl::SNIOC_POWERUP - "
                    "mcp9844_read_u16 failed\n");
            }
        }
        break;

      default:
        snerr("ERROR: Unrecognized cmd: %d\n", cmd);
        ret = -ENOTTY;
        break;
    }

  return ret;
}

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

/****************************************************************************
 * Name: mcp9844_register
 *
 * Description:
 *   Register the MCP9844 character device as 'devpath'
 *
 * Input Parameters:
 *   devpath - The full path to the driver to register. E.g., "/dev/temp0"
 *   i2c - An instance of the I2C interface to use to communicate with
 *         MCP9844
 *   addr - The I2C address of the MCP9844.
 *
 * Returned Value:
 *   Zero (OK) on success; a negated errno value on failure.
 *
 ****************************************************************************/

int mcp9844_register(FAR const char *devpath, FAR struct i2c_master_s *i2c,
                     uint8_t addr)
{
  FAR struct mcp9844_dev_s *priv;

  /* Sanity check */

  DEBUGASSERT(i2c != NULL);

  /* Initialize the MCP9844 device structure */

  priv = kmm_malloc(sizeof(struct mcp9844_dev_s));
  if (priv == NULL)
    {
      snerr("ERROR: Failed to allocate instance\n");
      return -ENOMEM;
    }

  priv->i2c  = i2c;
  priv->addr = addr;

  /* Register the character driver */

  int ret = register_driver(devpath, &g_mcp9844_fops, 0666, priv);
  if (ret < 0)
    {
      snerr("ERROR: Failed to register driver: %d\n", ret);
      kmm_free(priv);
    }

  return ret;
}
#endif /* CONFIG_I2C && CONFIG_LM75_I2C */