335 lines
10 KiB
C
335 lines
10 KiB
C
/****************************************************************************
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* drivers/sensors/max31865.c
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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/* Character driver for the Maxim MAX31865 Thermocouple-to-Digital Converter
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*
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* NOTE: Some Maxim MAX31865 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/max31865-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 <inttypes.h>
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#include <stdlib.h>
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#include <fixedmath.h>
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#include <assert.h>
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#include <errno.h>
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#include <debug.h>
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#include <math.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/max31865.h>
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#include <nuttx/random.h>
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#include <sys/endian.h>
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#if defined(CONFIG_SPI) && defined(CONFIG_SENSORS_MAX31865)
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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 MAX31865_CONFIG_REG 0x00
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# define MAX31865_BIAS_ON (1 << 7)
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# define MAX31865_AUTO_CONVERSION (1 << 6)
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# define MAX31865_ONE_SHOT (1 << 5)
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# define MAX31865_3WIRE (1 << 4)
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# define MAX31865_FAULT_DET_OFFSET (2)
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# define MAX31865_FAULT_DET_MASK (3 << MAX31865_FAULT_DET_OFFSET)
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# define MAX31865_FAULT_DET_OFF (0 << MAX31865_FAULT_DET_OFFSET)
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# define MAX31865_FAULT_DET_AUTO (1 << MAX31865_FAULT_DET_OFFSET)
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# define MAX31865_FAULT_DET_1CYCLE (2 << MAX31865_FAULT_DET_OFFSET)
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# define MAX31865_FAULT_DET_2CYCLE (3 << MAX31865_FAULT_DET_OFFSET)
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# define MAX31865_FAULT_STATUS_CLR (1 << 1)
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# define MAX31865_50HZ_FILTER (1 << 0)
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#define MAX31865_RTDMSB_REG 0x01
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#define MAX31865_RTDLSB_REG 0x02
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#define MAX31865_HFAULTMSB_REG 0x03
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#define MAX31865_HFAULTLSB_REG 0x04
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#define MAX31865_LFAULTMSB_REG 0x05
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#define MAX31865_LFAULTLSB_REG 0x06
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#define MAX31865_FAULTSTAT_REG 0x07
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#define MAX31865_REF_RESISTOR 430
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#define MAX31865_WRITE 0x80
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#define RTD_A (3.9083e-3)
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#define RTD_B (-5.775e-7)
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struct max31865_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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uint16_t devid; /* Select minor device number */
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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 max31865_lock(FAR struct spi_dev_s *spi);
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static void max31865_unlock(FAR struct spi_dev_s *spi);
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/* Character driver methods */
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static int max31865_open(FAR struct file *filep);
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static ssize_t max31865_read(FAR struct file *filep, FAR char *buffer,
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size_t buflen);
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static ssize_t max31865_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_max31865fops =
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{
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max31865_open, /* open */
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NULL, /* close */
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max31865_read, /* read */
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max31865_write, /* write */
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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: max31865_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 max31865_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_MODE1);
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SPI_SETBITS(spi, 8);
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SPI_HWFEATURES(spi, 0);
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SPI_SETFREQUENCY(spi, 400000);
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}
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/****************************************************************************
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* Name: max31865_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 max31865_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: max31865_open
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*
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* Description:
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* This function is called whenever the MAX31865 device is opened.
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*
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****************************************************************************/
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static int max31865_open(FAR struct file *filep)
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{
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FAR struct inode *inode = filep->f_inode;
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FAR struct max31865_dev_s *priv = inode->i_private;
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unsigned char regval;
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/* Enable MAX31865's chip select */
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max31865_lock(priv->spi);
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SPI_SELECT(priv->spi, SPIDEV_TEMPERATURE(priv->devid), true);
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regval = MAX31865_WRITE | MAX31865_CONFIG_REG;
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SPI_SEND(priv->spi, regval);
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regval = MAX31865_50HZ_FILTER | MAX31865_3WIRE | \
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MAX31865_AUTO_CONVERSION | MAX31865_BIAS_ON;
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SPI_SEND(priv->spi, regval);
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/* Disable MAX31865's chip select */
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SPI_SELECT(priv->spi, SPIDEV_TEMPERATURE(priv->devid), false);
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max31865_unlock(priv->spi);
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return OK;
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}
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/****************************************************************************
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* Name: max31865_read
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****************************************************************************/
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static ssize_t max31865_read(FAR struct file *filep, FAR char *buffer,
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size_t buflen)
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{
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FAR struct inode *inode = filep->f_inode;
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FAR struct max31865_dev_s *priv = inode->i_private;
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uint8_t regval[8];
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float temp;
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uint16_t regmsb;
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float rt;
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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 != sizeof(float))
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{
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snerr("ERROR: You can't read something other than 16 bits "
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"(2 bytes)\n");
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return -EINVAL;
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}
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/* Enable MAX31865's chip select */
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max31865_lock(priv->spi);
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SPI_SELECT(priv->spi, SPIDEV_TEMPERATURE(priv->devid), true);
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/* Read temperature */
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memset(regval, 0, sizeof(regval));
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SPI_SEND(priv->spi, MAX31865_CONFIG_REG);
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SPI_RECVBLOCK(priv->spi, regval, sizeof(regval));
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/* Disable MAX31865's chip select */
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SPI_SELECT(priv->spi, SPIDEV_TEMPERATURE(priv->devid), false);
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max31865_unlock(priv->spi);
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/* Detect any errors during SPI transmission */
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if (*regval != (MAX31865_50HZ_FILTER | MAX31865_3WIRE | \
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MAX31865_AUTO_CONVERSION | MAX31865_BIAS_ON))
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{
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snerr("ERROR: Data transmission failed on device %d:\n", priv->devid);
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snerr(" One or more MAX31865 pins are not properly connected!\n\n");
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return -EINVAL;
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}
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/* Resistance of the RTD */
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regmsb = ((regval[1] << 8) | regval[2]) >> 1;
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rt = (float)(regmsb * MAX31865_REF_RESISTOR / 32768.0);
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/* T = (-A + sqrt(A^2 - 4*B*(1 - R/R0))) / (2*B) */
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temp = (-RTD_A + sqrt(RTD_A * RTD_A - 4 * RTD_B * (1 - rt / 100.0))) \
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/ (2 * RTD_B);
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*(float *)buffer = temp;
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sninfo("MAX31865 ADC: %d, RTD: %.2f, temperature: %.1f\n", \
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regmsb, rt, temp);
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return sizeof(temp);
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}
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/****************************************************************************
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* Name: max31865_write
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****************************************************************************/
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static ssize_t max31865_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: max31865_register
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*
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* Description:
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* This function will register the max31865 driver as /dev/tempN
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* where N is the minor device number
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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 SPI interface to use to communicate with
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* MAX31865
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* devid - Minor device number. E.g., 0, 1, 2, etc.
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*
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* Returned Value:
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* Zero is returned on success. Otherwise, a negated errno value is
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* returned to indicate the nature of the failure.
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*
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****************************************************************************/
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int max31865_register(FAR const char *devpath, FAR struct spi_dev_s *spi,
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uint16_t devid)
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{
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FAR struct max31865_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 MAX31865 device structure */
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priv = (FAR struct max31865_dev_s *)
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kmm_malloc(sizeof(struct max31865_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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priv->devid = devid;
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/* Register the character driver */
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ret = register_driver(devpath, &g_max31865fops, 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_MAX31865 */
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