/****************************************************************************
* drivers/sensors/max31855.c
* Character driver for the Maxim MAX31855 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 MAX31855 chips have an issue it report value 25% lower
* of real temperature, for more info read this thread:
* http://www.eevblog.com/forum/projects/max31855-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/max31855.h>
#if defined(CONFIG_SPI) && defined(CONFIG_MAX31855)
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/****************************************************************************
* Private
****************************************************************************/
#define MAX31855_FAULT (1 << 16)
#define MAX31855_SHORT_VCC (1 << 2)
#define MAX31855_SHORT_GND (1 << 1)
#define MAX31855_OPEN_CIRCUIT (1 << 0)
#define MAX31855_TEMP_COUPLE 0xFFFFC000
#define MAX31855_TEMP_JUNCTION 0xFFF0
struct max31855_dev_s
{
FAR struct spi_dev_s *spi; /* Saved SPI driver instance */
int16_t temp;
};
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
static void max31855_lock(FAR struct spi_dev_s *spi);
static void max31855_unlock(FAR struct spi_dev_s *spi);
/* Character driver methods */
static int max31855_open(FAR struct file *filep);
static int max31855_close(FAR struct file *filep);
static ssize_t max31855_read(FAR struct file *filep, FAR char *buffer,
size_t buflen);
static ssize_t max31855_write(FAR struct file *filep, FAR const char *buffer,
size_t buflen);
/****************************************************************************
* Private Data
****************************************************************************/
static const struct file_operations g_max31855fops =
{
max31855_open,
max31855_close,
max31855_read,
max31855_write,
NULL,
NULL
#ifndef CONFIG_DISABLE_POLL
, NULL
#endif
};
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: max31855_lock
*
* Description:
* Lock and configure the SPI bus.
*
****************************************************************************/
static void max31855_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: max31855_unlock
*
* Description:
* Unlock the SPI bus.
*
****************************************************************************/
static void max31855_unlock(FAR struct spi_dev_s *spi)
{
(void)SPI_LOCK(spi, false);
}
/****************************************************************************
* Name: max31855_open
*
* Description:
* This function is called whenever the MAX31855 device is opened.
*
****************************************************************************/
static int max31855_open(FAR struct file *filep)
{
return OK;
}
/****************************************************************************
* Name: max31855_close
*
* Description:
* This routine is called when the MAX31855 device is closed.
*
****************************************************************************/
static int max31855_close(FAR struct file *filep)
{
return OK;
}
/****************************************************************************
* Name: max31855_read
****************************************************************************/
static ssize_t max31855_read(FAR struct file *filep, FAR char *buffer, size_t buflen)
{
FAR struct inode *inode = filep->f_inode;
FAR struct max31855_dev_s *priv = inode->i_private;
FAR uint16_t *temp = (FAR uint16_t *) buffer;
int ret = 2;
int32_t regmsb;
int32_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 MAX31855's chip select */
max31855_lock(priv->spi);
SPI_SELECT(priv->spi, SPIDEV_TEMPERATURE, true);
/* Read temperature */
SPI_RECVBLOCK(priv->spi, ®msb, 4);
/* Disable MAX31855's chip select */
SPI_SELECT(priv->spi, SPIDEV_TEMPERATURE, false);
max31855_unlock(priv->spi);
regval = (regmsb & 0xFF000000) >> 24;
regval |= (regmsb & 0xFF0000) >> 8;
regval |= (regmsb & 0xFF00) << 8;
regval |= (regmsb & 0xFF) << 24;
sninfo("Read from MAX31855 = 0x%08X\n", regval);
/* If negative, fix signal bits */
if (regval & 0x80000000)
{
*temp = 0xc000 | (regval >> 18);
}
else
{
*temp = (regval >> 18);
}
/* Detect any fault */
if (regval & MAX31855_FAULT)
{
snerr("ERROR: A fault was detected by MAX31855:\n");
if (regval & MAX31855_SHORT_VCC)
{
snerr(" The thermocouple input is shorted to VCC!\n");
}
if (regval & MAX31855_SHORT_GND)
{
snerr(" The thermocouple input is shorted to GND!\n");
}
if (regval & MAX31855_OPEN_CIRCUIT)
{
snerr(" The thermocouple input is not connected!\n");
}
ret = -EINVAL;
}
/* Return two bytes, the temperature is fixed point Q12.2, then divide by 4
* in your application in other to get real temperature in Celsius degrees.
*/
return ret;
}
/****************************************************************************
* Name: max31855_write
****************************************************************************/
static ssize_t max31855_write(FAR struct file *filep, FAR const char *buffer,
size_t buflen)
{
return -ENOSYS;
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: max31855_register
*
* Description:
* Register the MAX31855 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 wit
* MAX31855 addr - The I2C address of the MAX31855. The base I2C address
* of the MAX31855 is 0x48. Bits 0-3 can be controlled to get 8 unique
* addresses from 0x48 through 0x4f.
*
* Returned Value:
* Zero (OK) on success; a negated errno value on failure.
*
****************************************************************************/
int max31855_register(FAR const char *devpath, FAR struct spi_dev_s *spi)
{
FAR struct max31855_dev_s *priv;
int ret;
/* Sanity check */
DEBUGASSERT(spi != NULL);
/* Initialize the MAX31855 device structure */
priv = (FAR struct max31855_dev_s *)kmm_malloc(sizeof(struct max31855_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_max31855fops, 0666, priv);
if (ret < 0)
{
snerr("ERROR: Failed to register driver: %d\n", ret);
kmm_free(priv);
}
return ret;
}
#endif /* CONFIG_SPI && CONFIG_MAX31855 */