/****************************************************************************
* drivers/sensors/max6675.c
* Character driver for the Maxim MAX6675 Thermocouple-to-Digital Converter
*
* Copyright (C) 2015 Alan Carvalho de Assis. All rights reserved.
* Author: Alan Carvalho de Assis <acassis@extern.io>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************/
/* NOTE: Some Maxim MAX6675 chips have an issue it report value 25% lower
* of real temperature, for more info read this thread:
* http://www.eevblog.com/forum/projects/max6675-temperature-error/
*/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <stdlib.h>
#include <fixedmath.h>
#include <errno.h>
#include <debug.h>
#include <nuttx/kmalloc.h>
#include <nuttx/fs/fs.h>
#include <nuttx/spi/spi.h>
#include <nuttx/sensors/max6675.h>
#if defined(CONFIG_SPI) && defined(CONFIG_MAX6675)
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/****************************************************************************
* Private
****************************************************************************/
#define MAX6675_THREE_STATE (1 << 0)
#define MAX6675_DEV_ID (1 << 1)
#define MAX6675_OPEN_CIRCUIT (1 << 2)
#define MAX6675_TEMP_COUPLE 0x7ff8
struct max6675_dev_s
{
FAR struct spi_dev_s *spi; /* Saved SPI driver instance */
int16_t temp;
};
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
static void max6675_lock(FAR struct spi_dev_s *spi)
static void max6675_unlock(FAR struct spi_dev_s *spi)
/* Character driver methods */
static int max6675_open(FAR struct file *filep);
static int max6675_close(FAR struct file *filep);
static ssize_t max6675_read(FAR struct file *, FAR char *, size_t);
static ssize_t max6675_write(FAR struct file *filep, FAR const char *buffer,
size_t buflen);
/****************************************************************************
* Private Data
****************************************************************************/
static const struct file_operations g_max6675fops =
{
max6675_open,
max6675_close,
max6675_read,
max6675_write,
NULL,
NULL
#ifndef CONFIG_DISABLE_POLL
, NULL
#endif
};
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: max6675_lock
*
* Description:
* Lock and configure the SPI bus.
*
****************************************************************************/
static void max6675_lock(FAR struct spi_dev_s *spi)
{
(void)SPI_LOCK(spi, true);
SPI_SETMODE(spi, SPIDEV_MODE0);
SPI_SETBITS(spi, 8);
(void)SPI_HWFEATURES(spi, 0);
SPI_SETFREQUENCY(spi, 400000);
}
/****************************************************************************
* Name: max6675_unlock
*
* Description:
* Unlock the SPI bus.
*
****************************************************************************/
static void max6675_unlock(FAR struct spi_dev_s *spi)
{
(void)SPI_LOCK(spi, false);
}
/****************************************************************************
* Name: max6675_open
*
* Description:
* This function is called whenever the MAX6675 device is opened.
*
****************************************************************************/
static int max6675_open(FAR struct file *filep)
{
return OK;
}
/****************************************************************************
* Name: max6675_close
*
* Description:
* This routine is called when the MAX6675 device is closed.
*
****************************************************************************/
static int max6675_close(FAR struct file *filep)
{
return OK;
}
/****************************************************************************
* Name: max6675_read
****************************************************************************/
static ssize_t max6675_read(FAR struct file *filep, FAR char *buffer, size_t buflen)
{
FAR struct inode *inode = filep->f_inode;
FAR struct max6675_dev_s *priv = inode->i_private;
FAR uint16_t *temp = (FAR uint16_t *) buffer;
int ret = 2;
int16_t regmsb;
int16_t regval;
/* Check for issues */
if (!buffer)
{
snerr("ERROR: Buffer is null\n");
return -EINVAL;
}
if (buflen != 2)
{
snerr("ERROR: You can't read something other than 16 bits (2 bytes)\n");
return -EINVAL;
}
/* Enable MAX6675's chip select */
max6675_lock(priv->spi);
SPI_SELECT(priv->spi, SPIDEV_TEMPERATURE, true);
/* Read temperature */
SPI_RECVBLOCK(priv->spi, ®msb, 2);
/* Disable MAX6675's chip select */
SPI_SELECT(priv->spi, SPIDEV_TEMPERATURE, false);
max6675_unlock(priv->spi);
regval = (regmsb & 0xFF00) >> 8;
regval |= (regmsb & 0xFF) << 8;
sninfo("Read from MAX6675 = 0x%04X\n", regval);
/* Verify if the device ID bit is really zero */
if (regval & MAX6675_DEV_ID)
{
snerr("ERROR: The Device ID bit needs to be 0 !\n");
ret = -EINVAL;
}
/* Detect if termocople input is open */
if (regval & MAX6675_OPEN_CIRCUIT)
{
snerr("ERROR: The thermocouple input is not connected!\n");
ret = -EINVAL;
}
/* Get the temperature */
*temp = (regval & MAX6675_TEMP_COUPLE) >> 3;
/* Return two bytes, the temperature is fixed point Q10.2, then divide by 4
* in your application in order to get real temperature in Celsius degrees.
*/
return ret;
}
/****************************************************************************
* Name: max6675_write
****************************************************************************/
static ssize_t max6675_write(FAR struct file *filep, FAR const char *buffer,
size_t buflen)
{
return -ENOSYS;
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: max6675_register
*
* Description:
* Register the MAX6675 character device as 'devpath'
*
* Input Parameters:
* devpath - The full path to the driver to register. E.g., "/dev/temp0"
* spi - An instance of the SPU interface to use to communicate with
* MAX6675.
*
* Returned Value:
* Zero (OK) on success; a negated errno value on failure.
*
****************************************************************************/
int max6675_register(FAR const char *devpath, FAR struct spi_dev_s *spi)
{
FAR struct max6675_dev_s *priv;
int ret;
/* Sanity check */
DEBUGASSERT(spi != NULL);
/* Initialize the MAX6675 device structure */
priv = (FAR struct max6675_dev_s *)kmm_malloc(sizeof(struct max6675_dev_s));
if (priv == NULL)
{
snerr("ERROR: Failed to allocate instance\n");
return -ENOMEM;
}
priv->spi = spi;
priv->temp = 0;
/* Register the character driver */
ret = register_driver(devpath, &g_max6675fops, 0666, priv);
if (ret < 0)
{
snerr("ERROR: Failed to register driver: %d\n", ret);
kmm_free(priv);
}
return ret;
}
#endif /* CONFIG_SPI && CONFIG_MAX6675 */