310 lines
9.2 KiB
C
310 lines
9.2 KiB
C
/****************************************************************************
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* drivers/sensors/max6675.c
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* Character driver for the Maxim MAX6675 Thermocouple-to-Digital Converter
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*
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* Copyright (C) 2015 Alan Carvalho de Assis. All rights reserved.
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* Author: Alan Carvalho de Assis <acassis@extern.io>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/* NOTE: Some Maxim MAX6675 chips have an issue it report value 25% lower
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* of real temperature, for more info read this thread:
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* http://www.eevblog.com/forum/projects/max6675-temperature-error/
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*/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <stdlib.h>
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#include <fixedmath.h>
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#include <errno.h>
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#include <debug.h>
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#include <nuttx/kmalloc.h>
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#include <nuttx/fs/fs.h>
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#include <nuttx/spi/spi.h>
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#include <nuttx/sensors/max6675.h>
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#include <nuttx/random.h>
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#if defined(CONFIG_SPI) && defined(CONFIG_SENSORS_MAX6675)
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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/****************************************************************************
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* Private
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****************************************************************************/
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#define MAX6675_THREE_STATE (1 << 0)
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#define MAX6675_DEV_ID (1 << 1)
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#define MAX6675_OPEN_CIRCUIT (1 << 2)
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#define MAX6675_TEMP_COUPLE 0x7ff8
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struct max6675_dev_s
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{
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FAR struct spi_dev_s *spi; /* Saved SPI driver instance */
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int16_t temp;
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};
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/****************************************************************************
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* Private Function Prototypes
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****************************************************************************/
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static void max6675_lock(FAR struct spi_dev_s *spi);
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static void max6675_unlock(FAR struct spi_dev_s *spi);
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/* Character driver methods */
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static int max6675_open(FAR struct file *filep);
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static int max6675_close(FAR struct file *filep);
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static ssize_t max6675_read(FAR struct file *, FAR char *, size_t);
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static ssize_t max6675_write(FAR struct file *filep, FAR const char *buffer,
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size_t buflen);
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/****************************************************************************
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* Private Data
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****************************************************************************/
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static const struct file_operations g_max6675fops =
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{
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max6675_open,
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max6675_close,
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max6675_read,
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max6675_write,
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NULL,
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NULL,
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NULL
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};
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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/****************************************************************************
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* Name: max6675_lock
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*
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* Description:
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* Lock and configure the SPI bus.
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*
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****************************************************************************/
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static void max6675_lock(FAR struct spi_dev_s *spi)
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{
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SPI_LOCK(spi, true);
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SPI_SETMODE(spi, SPIDEV_MODE0);
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SPI_SETBITS(spi, 8);
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SPI_HWFEATURES(spi, 0);
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SPI_SETFREQUENCY(spi, 4000000);
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}
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/****************************************************************************
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* Name: max6675_unlock
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*
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* Description:
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* Unlock the SPI bus.
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*
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****************************************************************************/
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static void max6675_unlock(FAR struct spi_dev_s *spi)
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{
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SPI_LOCK(spi, false);
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}
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/****************************************************************************
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* Name: max6675_open
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*
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* Description:
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* This function is called whenever the MAX6675 device is opened.
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*
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****************************************************************************/
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static int max6675_open(FAR struct file *filep)
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{
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return OK;
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}
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/****************************************************************************
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* Name: max6675_close
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*
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* Description:
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* This routine is called when the MAX6675 device is closed.
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*
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****************************************************************************/
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static int max6675_close(FAR struct file *filep)
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{
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return OK;
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}
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/****************************************************************************
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* Name: max6675_read
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****************************************************************************/
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static ssize_t max6675_read(FAR struct file *filep, FAR char *buffer, size_t buflen)
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{
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FAR struct inode *inode = filep->f_inode;
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FAR struct max6675_dev_s *priv = inode->i_private;
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FAR uint16_t *temp = (FAR uint16_t *) buffer;
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int ret = 2;
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int16_t regmsb;
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int16_t regval;
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/* Check for issues */
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if (!buffer)
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{
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snerr("ERROR: Buffer is null\n");
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return -EINVAL;
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}
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if (buflen != 2)
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{
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snerr("ERROR: You can't read something other than 16 bits (2 bytes)\n");
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return -EINVAL;
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}
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/* Enable MAX6675's chip select */
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max6675_lock(priv->spi);
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SPI_SELECT(priv->spi, SPIDEV_TEMPERATURE(0), true);
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/* Read temperature */
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SPI_RECVBLOCK(priv->spi, ®msb, 2);
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/* Disable MAX6675's chip select */
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SPI_SELECT(priv->spi, SPIDEV_TEMPERATURE(0), false);
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max6675_unlock(priv->spi);
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regval = (regmsb & 0xff00) >> 8;
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regval |= (regmsb & 0xff) << 8;
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sninfo("Read from MAX6675 = 0x%04X\n", regval);
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/* Verify if the device ID bit is really zero */
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if (regval & MAX6675_DEV_ID)
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{
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snerr("ERROR: The Device ID bit needs to be 0 !\n");
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ret = -EINVAL;
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}
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/* Detect if termocople input is open */
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if (regval & MAX6675_OPEN_CIRCUIT)
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{
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snerr("ERROR: The thermocouple input is not connected!\n");
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ret = -EINVAL;
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}
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/* Feed sensor data to entropy pool */
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add_sensor_randomness(regval);
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/* Get the temperature */
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*temp = (regval & MAX6675_TEMP_COUPLE) >> 3;
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/* Return two bytes, the temperature is fixed point Q10.2, then divide by 4
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* in your application in order to get real temperature in Celsius degrees.
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*/
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return ret;
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}
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/****************************************************************************
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* Name: max6675_write
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****************************************************************************/
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static ssize_t max6675_write(FAR struct file *filep, FAR const char *buffer,
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size_t buflen)
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{
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return -ENOSYS;
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}
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: max6675_register
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*
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* Description:
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* Register the MAX6675 character device as 'devpath'
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*
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* Input Parameters:
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* devpath - The full path to the driver to register. E.g., "/dev/temp0"
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* spi - An instance of the SPU interface to use to communicate with
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* MAX6675.
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*
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* Returned Value:
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* Zero (OK) on success; a negated errno value on failure.
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*
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****************************************************************************/
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int max6675_register(FAR const char *devpath, FAR struct spi_dev_s *spi)
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{
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FAR struct max6675_dev_s *priv;
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int ret;
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/* Sanity check */
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DEBUGASSERT(spi != NULL);
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/* Initialize the MAX6675 device structure */
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priv = (FAR struct max6675_dev_s *)kmm_malloc(sizeof(struct max6675_dev_s));
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if (priv == NULL)
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{
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snerr("ERROR: Failed to allocate instance\n");
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return -ENOMEM;
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}
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priv->spi = spi;
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priv->temp = 0;
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/* Register the character driver */
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ret = register_driver(devpath, &g_max6675fops, 0666, priv);
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if (ret < 0)
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{
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snerr("ERROR: Failed to register driver: %d\n", ret);
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kmm_free(priv);
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}
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return ret;
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}
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#endif /* CONFIG_SPI && CONFIG_SENSORS_MAX6675 */
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