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incubator-nuttx/drivers/sensors/scd41.c

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/****************************************************************************
* drivers/sensors/scd41.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 <stdint.h>
#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <assert.h>
#include <errno.h>
#include <time.h>
#include <debug.h>
#include <nuttx/kmalloc.h>
#include <nuttx/mutex.h>
#include <nuttx/signal.h>
#include <nuttx/fs/fs.h>
#include <nuttx/i2c/i2c_master.h>
#include <nuttx/sensors/scd41.h>
#include <nuttx/random.h>
#if defined(CONFIG_SENSORS_SCD41)
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
#ifdef CONFIG_SCD41_DEBUG
# define scd41_dbg(x, ...) _info(x, ##__VA_ARGS__)
#else
# define scd41_dbg(x, ...) sninfo(x, ##__VA_ARGS__)
#endif
#ifndef CONFIG_SCD41_I2C_FREQUENCY
# define CONFIG_SCD41_I2C_FREQUENCY 100000
#endif
#define SCD41_I2C_RETRIES 3
/* SCD41 command words */
#define SCD41_CMD_START_MEASUREMENT 0x21b1
#define SCD41_CMD_STOP_MEASUREMENT 0x3f86
#define SCD41_CMD_GET_DATA_READY 0xe4b8
#define SCD41_CMD_READ_MEASUREMENT 0xec05
#define SCD41_CMD_SET_ASC 0x2416
#define SCD41_CMD_GET_ASC 0x2313
#define SCD41_CMD_SET_FRC 0x362f
#define SCD41_CMD_SET_TEMP_OFFSET 0x241d
#define SCD41_CMD_GET_TEMP_OFFSET 0x2318
#define SCD41_CMD_SET_ALT_COMPENSATION 0x2427
#define SCD41_CMD_GET_ALT_COMPENSATION 0x2322
#define SCD41_CMD_SET_PRESSURE_COMP 0xe000
#define SCD41_CMD_SOFT_RESET 0x3646
#define SCD41_CMD_LOWPOWER_MODE 0x21ac
#define SCD41_CMD_PERSIST_SETTINGS 0x3615
#define SCD41_CMD_GET_SERIAL_NUMBER 0x3682
#define SCD41_CMD_START_SELFTEST 0x3639
#define SCD41_CMD_FACTORY_RESET 0x3632
#define SCD41_CMD_ONESHOT_MEASUREMENT 0x219d
#define SCD41_CMD_ONESHOT_MEASURE_RHT 0x2196
#define SCD41_DEFAULT_MEASUREMENT_INTERVAL 5 /* seconds */
#define SCD41_DEFAULT_PRESSURE_COMPENSATION 0
#define SCD41_DEFAULT_ALTITUDE_COMPENSATION 0
#define SCD41_DEFAULT_TEMPERATURE_OFFSET 0
/****************************************************************************
* Private
****************************************************************************/
struct scd41_dev_s
{
#ifdef CONFIG_SCD41_I2C
FAR struct i2c_master_s *i2c; /* I2C interface */
uint8_t addr; /* I2C address */
#endif
bool valid; /* If cached readings are valid */
bool started; /* If continuous measurement is enabled */
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
bool unlinked; /* True, driver has been unlinked */
#endif
struct timespec last_update; /* Last time when sensor was read */
float co2; /* Cached CO₂ (PPM) */
float temperature; /* Cached temperature (°C) */
float humidity; /* Cached humidity (RH%) */
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
int16_t crefs; /* Number of open references */
#endif
mutex_t devlock;
uint16_t pressure_comp; /* Pressure compensation in mbar (non-zero
* value overrides altitude compensation). */
uint16_t altitude_comp; /* Altitude compensation in meters */
uint16_t interval; /* Background measurement interval in
* seconds (2 to 1800). */
uint16_t temperature_offset; /* Temperature offset in 0.01 Kelvin. */
};
struct scd41_word_s
{
uint8_t data[2];
uint8_t crc;
};
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
/* IO Helpers */
#ifdef CONFIG_SCD41_I2C
static int scd41_do_transfer(FAR struct i2c_master_s *i2c,
FAR struct i2c_msg_s *msgv,
size_t nmsg);
#endif
static int scd41_write_cmd(FAR struct scd41_dev_s *priv, uint16_t cmd,
FAR struct scd41_word_s *params,
unsigned int num_params);
static int scd41_read_words(FAR struct scd41_dev_s *priv,
FAR struct scd41_word_s *words,
unsigned int num_words);
/* Data conversion */
static uint8_t scd41_crc_word(uint16_t word);
static void scd41_set_command_param(FAR struct scd41_word_s *param,
uint16_t value);
static int scd41_check_data_crc(FAR const struct scd41_word_s *words,
unsigned int num_words);
static uint16_t scd41_data_word2uint16(FAR const struct scd41_word_s *word);
/* Driver features */
static int scd41_read_values(FAR struct scd41_dev_s *priv, FAR float *temp,
FAR float *rh, FAR float *co2, bool wait);
static int scd41_configure(FAR struct scd41_dev_s *priv, bool start);
/* Character driver methods */
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
static int scd41_open(FAR struct file *filep);
static int scd41_close(FAR struct file *filep);
#endif
static ssize_t scd41_read(FAR struct file *filep, FAR char *buffer,
size_t buflen);
static ssize_t scd41_write(FAR struct file *filep, FAR const char *buffer,
size_t buflen);
static int scd41_ioctl(FAR struct file *filep, int cmd,
unsigned long arg);
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
static int scd41_unlink(FAR struct inode *inode);
#endif
/****************************************************************************
* Private Data
****************************************************************************/
static const struct file_operations g_scd41fops =
{
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
scd41_open, /* open */
scd41_close, /* close */
#else
NULL, /* open */
NULL, /* close */
#endif
scd41_read, /* read */
scd41_write, /* write */
NULL, /* seek */
scd41_ioctl, /* ioctl */
NULL, /* mmap */
NULL, /* truncate */
NULL /* poll */
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
, scd41_unlink /* unlink */
#endif
};
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: scd41_do_transfer
****************************************************************************/
#ifdef CONFIG_SCD41_I2C
static int scd41_do_transfer(FAR struct i2c_master_s *i2c,
FAR struct i2c_msg_s *msgv,
size_t nmsg)
{
int ret = -EIO;
int retries;
for (retries = 0; retries < SCD41_I2C_RETRIES; retries++)
{
ret = I2C_TRANSFER(i2c, msgv, nmsg);
if (ret >= 0)
{
return 0;
}
else
{
/* Some error. Try to reset I2C bus and keep trying. */
#ifdef CONFIG_I2C_RESET
if (retries == SCD41_I2C_RETRIES - 1)
{
break;
}
ret = I2C_RESET(i2c);
if (ret < 0)
{
scd41_dbg("I2C_RESET failed: %d\n", ret);
return ret;
}
#endif
}
}
scd41_dbg("xfer failed: %d\n", ret);
return ret;
}
#endif
/****************************************************************************
* Name: scd41_write_cmd
****************************************************************************/
static int scd41_write_cmd(FAR struct scd41_dev_s *priv, uint16_t cmd,
FAR struct scd41_word_s *params,
unsigned int num_params)
{
#ifdef CONFIG_SCD41_I2C
struct i2c_msg_s msg[2];
uint8_t cmd_buf[2];
int ret;
cmd_buf[0] = cmd >> 8;
cmd_buf[1] = cmd >> 0;
msg[0].frequency = CONFIG_SCD41_I2C_FREQUENCY;
msg[0].addr = priv->addr;
msg[0].flags = 0;
msg[0].buffer = cmd_buf;
msg[0].length = 2;
if (num_params)
{
msg[1].frequency = CONFIG_SCD41_I2C_FREQUENCY;
msg[1].addr = priv->addr;
msg[1].flags = I2C_M_NOSTART;
msg[1].buffer = (FAR uint8_t *)params;
msg[1].length = num_params * sizeof(*params);
}
ret = scd41_do_transfer(priv->i2c, msg, (num_params) ? 2 : 1);
scd41_dbg("cmd: 0x%04X num_params: %d ret: %d\n",
cmd, num_params, ret);
return (ret >= 0) ? OK : ret;
#else
/* UART mode not implemented yet. */
return -ENODEV;
#endif
}
/****************************************************************************
* Name: scd41_read_words
****************************************************************************/
static int scd41_read_words(FAR struct scd41_dev_s *priv,
FAR struct scd41_word_s *words,
unsigned int num_words)
{
#ifdef CONFIG_SCD41_I2C
struct i2c_msg_s msg[1];
int ret;
msg[0].frequency = CONFIG_SCD41_I2C_FREQUENCY;
msg[0].addr = priv->addr;
msg[0].flags = I2C_M_READ;
msg[0].buffer = (FAR uint8_t *)words;
msg[0].length = num_words * sizeof(*words);
ret = scd41_do_transfer(priv->i2c, msg, 1);
scd41_dbg("num_words: %d ret: %d\n", num_words, ret);
return (ret >= 0) ? OK : ret;
#else
/* UART mode not implemented yet. */
return -ENODEV;
#endif
}
/****************************************************************************
* Name: scd41_crc_word
****************************************************************************/
static uint8_t scd41_crc_word(uint16_t word)
{
static const uint8_t crc_table[16] =
{
0x00, 0x31, 0x62, 0x53, 0xc4, 0xf5, 0xa6, 0x97,
0xb9, 0x88, 0xdb, 0xea, 0x7d, 0x4c, 0x1f, 0x2e
};
uint8_t crc = 0xff;
crc ^= word >> 8;
crc = (crc << 4) ^ crc_table[crc >> 4];
crc = (crc << 4) ^ crc_table[crc >> 4];
crc ^= word >> 0;
crc = (crc << 4) ^ crc_table[crc >> 4];
crc = (crc << 4) ^ crc_table[crc >> 4];
return crc;
}
/****************************************************************************
* Name: scd41_set_command_param
****************************************************************************/
static void scd41_set_command_param(FAR struct scd41_word_s *param,
uint16_t value)
{
param->data[0] = value >> 8;
param->data[1] = value >> 0;
param->crc = scd41_crc_word(value);
}
/****************************************************************************
* Name: scd41_data_word2uint16
****************************************************************************/
static uint16_t scd41_data_word2uint16(FAR const struct scd41_word_s *word)
{
return (word[0].data[0] << 8) | (word[0].data[1]);
}
/****************************************************************************
* Name: scd41_crc_word
****************************************************************************/
static int scd41_check_data_crc(FAR const struct scd41_word_s *words,
unsigned int num_words)
{
while (num_words)
{
if (scd41_crc_word(scd41_data_word2uint16(words)) != words->crc)
{
return -1;
}
num_words--;
words++;
}
return 0;
}
/****************************************************************************
* Name: scd41_softreset
*
* Description:
* Reset the SCD41 sensor. This takes less than 2000 ms.
*
****************************************************************************/
static int scd41_softreset(FAR struct scd41_dev_s *priv)
{
int ret;
ret = scd41_write_cmd(priv, SCD41_CMD_SOFT_RESET, NULL, 0);
if (ret < 0)
{
return ret;
}
return 0;
}
/****************************************************************************
* Name: has_time_passed
*
* Description:
* Return true if curr >= start + secs_since_start
*
****************************************************************************/
static bool has_time_passed(struct timespec curr,
struct timespec start,
unsigned int secs_since_start)
{
if ((long)((start.tv_sec + secs_since_start) - curr.tv_sec) == 0)
{
return start.tv_nsec <= curr.tv_nsec;
}
return (long)((start.tv_sec + secs_since_start) - curr.tv_sec) <= 0;
}
/****************************************************************************
* Name: scd41_read_values
****************************************************************************/
static int scd41_read_values(FAR struct scd41_dev_s *priv, FAR float *temp,
FAR float *rh, FAR float *co2, bool wait)
{
struct scd41_word_s data[3];
struct timespec ts;
int ret;
clock_systime_timespec(&ts);
if (wait || !priv->valid ||
has_time_passed(ts, priv->last_update,
SCD41_DEFAULT_MEASUREMENT_INTERVAL))
{
while (1)
{
/* Wait data to be ready. */
ret = scd41_write_cmd(priv, SCD41_CMD_GET_DATA_READY, NULL, 0);
if (ret < 0)
{
scd41_dbg("ERROR: scd41_write_cmd failed: %d\n", ret);
return ret;
}
ret = scd41_read_words(priv, data, 1);
if (ret < 0)
{
scd41_dbg("ERROR: scd41_read_words failed: %d\n", ret);
return ret;
}
if (scd41_check_data_crc(data, 1) < 0)
{
scd41_dbg("ERROR: scd41_read_words crc failed\n");
ret = -EIO;
return ret;
}
if ((scd41_data_word2uint16(data) & 0x07ff) == 0x0000)
{
if (!wait)
{
scd41_dbg("ERROR: data not ready\n");
ret = -EAGAIN;
return ret;
}
ret = nxsig_usleep(500 * 1000);
if (ret == -EINTR)
{
return ret;
}
}
else
{
break;
}
}
/* Read the raw data */
ret = scd41_write_cmd(priv, SCD41_CMD_READ_MEASUREMENT, NULL, 0);
if (ret < 0)
{
scd41_dbg("ERROR: scd41_write_cmd failed: %d\n", ret);
return ret;
}
ret = scd41_read_words(priv, data, 3);
if (ret < 0)
{
scd41_dbg("ERROR: scd41_read_words failed: %d\n", ret);
return ret;
}
if (scd41_check_data_crc(data, 3) < 0)
{
scd41_dbg("ERROR: scd41_read_words crc failed\n");
ret = -EIO;
return ret;
}
add_sensor_randomness((data[0].crc << 16) ^ (data[1].crc << 8) ^
data[2].crc);
priv->co2 = (float)scd41_data_word2uint16(data + 0);
uint16_t tval = scd41_data_word2uint16(data + 1);
priv->temperature = (float)((tval * 175.0) / 65536.0 - 45.0);
uint16_t hval = scd41_data_word2uint16(data + 2);
priv->humidity = (float)(hval * 100.0 / 65536.0);
priv->last_update = ts;
priv->valid = true;
}
*temp = priv->temperature;
*rh = priv->humidity;
*co2 = priv->co2;
return OK;
}
/****************************************************************************
* Name: scd41_configure
****************************************************************************/
static int scd41_configure(FAR struct scd41_dev_s *priv, bool start)
{
struct scd41_word_s param;
int ret = OK;
/* Set altitude compensation. */
scd41_set_command_param(&param, priv->altitude_comp);
scd41_write_cmd(priv, SCD41_CMD_SET_ALT_COMPENSATION, &param, 1);
/* Set temperature offset. */
scd41_set_command_param(&param, priv->temperature_offset);
scd41_write_cmd(priv, SCD41_CMD_SET_TEMP_OFFSET, &param, 1);
/* Set pressure compensation. */
scd41_set_command_param(&param, priv->pressure_comp);
scd41_write_cmd(priv, SCD41_CMD_SET_PRESSURE_COMP, &param, 1);
if (start)
{
/* Start measurements. */
ret = scd41_write_cmd(priv, SCD41_CMD_START_MEASUREMENT, NULL, 0);
if (ret >= 0)
{
priv->started = true;
}
}
return ret;
}
/****************************************************************************
* Name: scd41_open
*
* Description:
* This function is called whenever the SCD41x device is opened.
*
****************************************************************************/
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
static int scd41_open(FAR struct file *filep)
{
FAR struct inode *inode = filep->f_inode;
FAR struct scd41_dev_s *priv = inode->i_private;
int ret = OK;
/* Get exclusive access */
ret = nxmutex_lock(&priv->devlock);
if (ret < 0)
{
return ret;
}
/* Increment the count of open references on the driver */
priv->crefs++;
DEBUGASSERT(priv->crefs > 0);
if (priv->crefs == 1)
{
ret = scd41_configure(priv, true);
}
if (ret < 0)
{
priv->crefs--;
}
nxmutex_unlock(&priv->devlock);
return ret;
}
#endif
/****************************************************************************
* Name: scd41_close
*
* Description:
* This routine is called when the SCD41 device is closed.
*
****************************************************************************/
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
static int scd41_close(FAR struct file *filep)
{
FAR struct inode *inode = filep->f_inode;
FAR struct scd41_dev_s *priv = inode->i_private;
int ret;
/* Get exclusive access */
ret = nxmutex_lock(&priv->devlock);
if (ret < 0)
{
return ret;
}
/* Decrement the count of open references on the driver */
DEBUGASSERT(priv->crefs > 0);
priv->crefs--;
/* If the count has decremented to zero and the driver has been unlinked,
* then free memory now.
*/
if (priv->crefs <= 0 && priv->unlinked)
{
nxmutex_destroy(&priv->devlock);
kmm_free(priv);
return OK;
}
nxmutex_unlock(&priv->devlock);
return OK;
}
#endif
/****************************************************************************
* Name: scd41_read
****************************************************************************/
static ssize_t scd41_read(FAR struct file *filep, FAR char *buffer,
size_t buflen)
{
FAR struct inode *inode = filep->f_inode;
FAR struct scd41_dev_s *priv = inode->i_private;
ssize_t length = 0;
float temp;
float rh;
float co2;
unsigned int temp100;
unsigned int rh100;
unsigned int co2_100;
int ret;
/* Get exclusive access */
ret = nxmutex_lock(&priv->devlock);
if (ret < 0)
{
return (ssize_t)ret;
}
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
if (priv->unlinked)
{
/* Do not allow operations on unlinked sensors. This allows
* sensor use on hot swappable I2C bus.
*/
nxmutex_unlock(&priv->devlock);
return -ENODEV;
}
#endif
if (!priv->started)
{
return -ENODATA;
}
ret = scd41_read_values(priv, &temp, &rh, &co2,
!(filep->f_oflags & O_NONBLOCK));
if (ret < 0)
{
scd41_dbg("cannot read data: %d\n", ret);
}
else
{
/* This interface is mainly intended for easy debugging in nsh. */
temp100 = abs(temp * 100);
rh100 = abs(rh * 100);
co2_100 = abs(co2 * 100);
length = snprintf(buffer, buflen, "%s%u.%02u %s%u.%02u %s%u.%02u\n",
co2 < 0 ? "-" : "", co2_100 / 100, co2_100 % 100,
temp < 0 ? "-" : "", temp100 / 100, temp100 % 100,
rh < 0 ? "-" : "", rh100 / 100, rh100 % 100);
if (length > buflen)
{
length = buflen;
}
}
nxmutex_unlock(&priv->devlock);
return length;
}
/****************************************************************************
* Name: scd41_write
****************************************************************************/
static ssize_t scd41_write(FAR struct file *filep, FAR const char *buffer,
size_t buflen)
{
return -ENOSYS;
}
/****************************************************************************
* Name: scd41_ioctl
****************************************************************************/
static int scd41_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
{
FAR struct inode *inode = filep->f_inode;
FAR struct scd41_dev_s *priv = inode->i_private;
struct scd41_word_s param;
int ret;
/* Get exclusive access */
ret = nxmutex_lock(&priv->devlock);
if (ret < 0)
{
return ret;
}
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
if (priv->unlinked)
{
/* Do not allow operations on unlinked sensors. This allows
* sensor use on hot swappable I2C bus.
*/
nxmutex_unlock(&priv->devlock);
return -ENODEV;
}
#endif
switch (cmd)
{
/* Soft reset the SCD41, Arg: None */
case SNIOC_RESET:
{
priv->interval = SCD41_DEFAULT_MEASUREMENT_INTERVAL;
priv->pressure_comp = SCD41_DEFAULT_PRESSURE_COMPENSATION;
priv->altitude_comp = SCD41_DEFAULT_ALTITUDE_COMPENSATION;
priv->temperature_offset = SCD41_DEFAULT_TEMPERATURE_OFFSET;
ret = scd41_softreset(priv);
scd41_dbg("softreset ret: %d\n", ret);
scd41_configure(priv, priv->started);
}
break;
/* Start background measurement, Arg: None */
case SNIOC_START:
{
/* Start measurements. */
ret = scd41_write_cmd(priv, SCD41_CMD_START_MEASUREMENT, NULL, 0);
if (ret >= 0)
{
priv->started = true;
}
}
break;
/* Stop background measurement, Arg: None */
case SNIOC_STOP:
{
/* Stop measurements. */
ret = scd41_write_cmd(priv, SCD41_CMD_STOP_MEASUREMENT, NULL, 0);
if (ret >= 0)
{
priv->started = false;
}
}
break;
/* Set temperature offset value, Arg: uint16_t */
case SNIOC_SET_TEMP_OFFSET:
{
if (arg > UINT16_MAX)
{
ret = -EINVAL;
break;
}
/* Actual Toffset = temperature_offset * 175.0 / 2^16 */
priv->temperature_offset = arg;
scd41_set_command_param(&param, priv->temperature_offset);
ret = scd41_write_cmd(priv, SCD41_CMD_SET_TEMP_OFFSET, &param, 1);
}
break;
/* Set pressure compensation value, Arg: uint16_t */
case SNIOC_SET_PRESSURE_COMP:
{
if (arg > UINT16_MAX)
{
ret = -EINVAL;
break;
}
priv->pressure_comp = arg;
scd41_set_command_param(&param, priv->pressure_comp);
ret = scd41_write_cmd(priv, SCD41_CMD_SET_PRESSURE_COMP,
&param, 1);
}
break;
/* Set altitude compensation value, Arg: uint16_t */
case SNIOC_SET_ALTITUDE_COMP:
{
if (arg > UINT16_MAX)
{
ret = -EINVAL;
break;
}
priv->altitude_comp = arg;
scd41_set_command_param(&param, priv->altitude_comp);
ret = scd41_write_cmd(priv, SCD41_CMD_SET_ALT_COMPENSATION,
&param, 1);
}
break;
/* Set Forced Recalibration value (FRC), Arg: uint16_t */
case SNIOC_SET_FRC:
{
if (arg > UINT16_MAX)
{
ret = -EINVAL;
break;
}
scd41_set_command_param(&param, arg);
ret = scd41_write_cmd(priv, SCD41_CMD_SET_FRC, &param, 1);
}
break;
/* (De-)Activate Automatic Self-Calibration (ASC), Arg: bool */
case SNIOC_ENABLE_ASC:
{
if (arg != !!arg) /* 0 or 1 */
{
ret = -EINVAL;
break;
}
scd41_set_command_param(&param, arg);
ret = scd41_write_cmd(priv, SCD41_CMD_SET_ASC, &param, 1);
}
break;
/* Read sensor data, Arg: struct scd41_conv_data_s *data */
case SNIOC_READ_CONVERT_DATA:
{
float temp;
float rh;
float co2;
ret = scd41_read_values(priv, &temp, &rh, &co2, false);
if (ret < 0)
{
scd41_dbg("cannot read data: %d\n", ret);
}
else
{
FAR struct scd41_conv_data_s *data =
(FAR struct scd41_conv_data_s *)arg;
data->temperature = temp;
data->humidity = rh;
data->co2 = co2;
}
}
break;
default:
scd41_dbg("Unrecognized cmd: %d\n", cmd);
ret = -ENOTTY;
break;
}
nxmutex_unlock(&priv->devlock);
return ret;
}
/****************************************************************************
* Name: scd41_unlink
****************************************************************************/
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
static int scd41_unlink(FAR struct inode *inode)
{
FAR struct scd41_dev_s *priv;
int ret;
DEBUGASSERT(inode->i_private != NULL);
priv = inode->i_private;
/* Get exclusive access */
ret = nxmutex_lock(&priv->devlock);
if (ret < 0)
{
return ret;
}
/* Are there open references to the driver data structure? */
if (priv->crefs <= 0)
{
nxmutex_destroy(&priv->devlock);
kmm_free(priv);
return OK;
}
/* No... just mark the driver as unlinked and free the resources when
* the last client closes their reference to the driver.
*/
priv->unlinked = true;
nxmutex_unlock(&priv->devlock);
return OK;
}
#endif
/****************************************************************************
* Public Functions
****************************************************************************/
#ifdef CONFIG_SCD41_I2C
/****************************************************************************
* Name: scd41_register_i2c
*
* Description:
* Register the SCD41 character device as 'devpath'
*
* Input Parameters:
* devpath - The full path to the driver to register. E.g., "/dev/co2_0"
* i2c - An instance of the I2C interface to use to communicate with
* the SCD41
*
* Returned Value:
* Zero (OK) on success; a negated errno value on failure.
*
****************************************************************************/
int scd41_register_i2c(FAR const char *devpath, FAR struct i2c_master_s *i2c)
{
FAR struct scd41_dev_s *priv;
int ret;
DEBUGASSERT(i2c != NULL);
DEBUGASSERT(scd41_crc_word(0xbeef) == 0x92);
/* Initialize the device structure */
priv = kmm_zalloc(sizeof(struct scd41_dev_s));
if (priv == NULL)
{
scd41_dbg("ERROR: Failed to allocate instance\n");
return -ENOMEM;
}
priv->i2c = i2c;
priv->addr = CONFIG_SCD41_ADDR;
priv->started = false;
priv->interval = SCD41_DEFAULT_MEASUREMENT_INTERVAL;
priv->pressure_comp = SCD41_DEFAULT_PRESSURE_COMPENSATION;
priv->altitude_comp = SCD41_DEFAULT_ALTITUDE_COMPENSATION;
priv->temperature_offset = SCD41_DEFAULT_TEMPERATURE_OFFSET;
nxmutex_init(&priv->devlock);
/* Register the character driver */
ret = register_driver(devpath, &g_scd41fops, 0666, priv);
if (ret < 0)
{
scd41_dbg("ERROR: Failed to register driver: %d\n", ret);
nxmutex_destroy(&priv->devlock);
kmm_free(priv);
}
return ret;
}
#endif /* CONFIG_SCD41_I2C */
#endif /* CONFIG_SENSORS_SCD41 */
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