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nuttx/drivers/sensors/sht4x.c
Matteo Golin 1fba2ec0df Add support for the Sensirion SHT4x temperature and humidity sensor family. 
This driver implements `read`, `write`, `open`, `close` and `ioctl`
interfaces to the SHT4X temperature and humidity sensor on an I2C bus.
The read implementation is that of a character driver for easy
debugging, while `ioctl` provides an interface to the sensor's raw data
collection and heating functionality.
2024-07-22 14:24:20 -03:00

856 lines
24 KiB
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/****************************************************************************
* drivers/sensors/sht4x.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 <debug.h>
#include <nuttx/clock.h>
#include <nuttx/config.h>
#include <nuttx/fs/fs.h>
#include <nuttx/i2c/i2c_master.h>
#include <nuttx/kmalloc.h>
#include <nuttx/mutex.h>
#include <nuttx/random.h>
#include <nuttx/sensors/sht4x.h>
#include <stdio.h>
#include <unistd.h>
#if defined(CONFIG_I2C) && defined(CONFIG_SENSORS_SHT4X)
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
#ifdef CONFIG_SHT4X_DEBUG
#define sht4x_dbg(x, ...) _info(x, ##__VA_ARGS__)
#endif
#if defined(CONFIG_SHT4X_FAHRENHEIT)
#define SHT4X_TEMP_UNIT "F"
#else
#define SHT4X_TEMP_UNIT "C"
#endif // defined(CONFIG_SHT4X_FAHRENHEIT)
#ifndef CONFIG_SHT4X_I2C_FREQUENCY
#define CONFIG_SHT4X_I2C_FREQUENCY 400000
#endif // CONFIG_SHT4X_I2C_FREQUENCY
#define SHT4X_CRC_INIT 0xFF /* Initial value of the calculated CRC. */
#define SHT4X_CRC_POLY 0x31 /* CRC calculation polynomial. */
#define SHT4X_SOFT_RESET 0x94 /* Soft reset command. */
#define SHT4X_READ_SERIAL 0x89 /* Read serial number command. */
#define SHT4X_READ_LOW_PREC 0xE0 /* Low precision read temp & humidity. */
#define SHT4X_READ_MED_PREC 0xF6 /* Med precision read temp & humidity. */
#define SHT4X_READ_HIGH_PREC 0xFD /* High precision read temp & humidity. */
#define SHT4X_HEAT_200_1 0x39 /* Activate heater with 200mW for 1s. */
#define SHT4X_HEAT_200_P1 0x32 /* Activate heater with 200mW for 0.1s. */
#define SHT4X_HEAT_110_1 0x2F /* Activate heater with 110mW for 1s. */
#define SHT4X_HEAT_110_P1 0x24 /* Activate heater with 110mW for 0.1s. */
#define SHT4X_HEAT_20_1 0x1E /* Activate heater with 20mW for 1s. */
#define SHT4X_HEAT_20_P1 0x15 /* Activate heater with 20mW for 0.1s. */
/****************************************************************************
* Private
****************************************************************************/
struct sht4x_dev_s
{
FAR struct i2c_master_s *i2c; /* I2C interface. */
uint8_t addr; /* I2C address. */
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
bool unlinked; /* True, driver has been unlinked. */
#endif // CONFIG_DISABLE_PSEUDOFS_OPERATIONS
struct timespec last_heat; /* Last time heater was active. */
enum sht4x_precision_e precision; /* The precision for read operations. */
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
int16_t crefs; /* Number of open references. */
#endif // CONFIG_DISABLE_PSEUDOFS_OPERATIONS
mutex_t devlock;
};
/* Easy unpacking of serial number from I2C packet. */
union sht4x_serialno_t
{
uint32_t full; /* Full serial number. */
struct
{
uint16_t msb; /* Most significant 2 bytes. */
uint16_t lsb; /* Least significant 2 bytes. */
} halves;
};
/****************************************************************************
* Private Data
****************************************************************************/
/* Commands for reading at different precisions */
static const uint8_t g_precision_read[] =
{
[SHT4X_PREC_LOW] = SHT4X_READ_LOW_PREC,
[SHT4X_PREC_MED] = SHT4X_READ_MED_PREC,
[SHT4X_PREC_HIGH] = SHT4X_READ_HIGH_PREC,
};
#ifdef CONFIG_SHT4X_CRC_LOOKUP
/* CRC lookup table. */
static const uint8_t g_crc_lookup[] =
{
0x0, 0x31, 0x62, 0x53, 0xc4, 0xf5, 0xa6, 0x97, 0xb9, 0x88, 0xdb,
0xea, 0x7d, 0x4c, 0x1f, 0x2e, 0x43, 0x72, 0x21, 0x10, 0x87, 0xb6,
0xe5, 0xd4, 0xfa, 0xcb, 0x98, 0xa9, 0x3e, 0xf, 0x5c, 0x6d, 0x86,
0xb7, 0xe4, 0xd5, 0x42, 0x73, 0x20, 0x11, 0x3f, 0xe, 0x5d, 0x6c,
0xfb, 0xca, 0x99, 0xa8, 0xc5, 0xf4, 0xa7, 0x96, 0x1, 0x30, 0x63,
0x52, 0x7c, 0x4d, 0x1e, 0x2f, 0xb8, 0x89, 0xda, 0xeb, 0x3d, 0xc,
0x5f, 0x6e, 0xf9, 0xc8, 0x9b, 0xaa, 0x84, 0xb5, 0xe6, 0xd7, 0x40,
0x71, 0x22, 0x13, 0x7e, 0x4f, 0x1c, 0x2d, 0xba, 0x8b, 0xd8, 0xe9,
0xc7, 0xf6, 0xa5, 0x94, 0x3, 0x32, 0x61, 0x50, 0xbb, 0x8a, 0xd9,
0xe8, 0x7f, 0x4e, 0x1d, 0x2c, 0x2, 0x33, 0x60, 0x51, 0xc6, 0xf7,
0xa4, 0x95, 0xf8, 0xc9, 0x9a, 0xab, 0x3c, 0xd, 0x5e, 0x6f, 0x41,
0x70, 0x23, 0x12, 0x85, 0xb4, 0xe7, 0xd6, 0x7a, 0x4b, 0x18, 0x29,
0xbe, 0x8f, 0xdc, 0xed, 0xc3, 0xf2, 0xa1, 0x90, 0x7, 0x36, 0x65,
0x54, 0x39, 0x8, 0x5b, 0x6a, 0xfd, 0xcc, 0x9f, 0xae, 0x80, 0xb1,
0xe2, 0xd3, 0x44, 0x75, 0x26, 0x17, 0xfc, 0xcd, 0x9e, 0xaf, 0x38,
0x9, 0x5a, 0x6b, 0x45, 0x74, 0x27, 0x16, 0x81, 0xb0, 0xe3, 0xd2,
0xbf, 0x8e, 0xdd, 0xec, 0x7b, 0x4a, 0x19, 0x28, 0x6, 0x37, 0x64,
0x55, 0xc2, 0xf3, 0xa0, 0x91, 0x47, 0x76, 0x25, 0x14, 0x83, 0xb2,
0xe1, 0xd0, 0xfe, 0xcf, 0x9c, 0xad, 0x3a, 0xb, 0x58, 0x69, 0x4,
0x35, 0x66, 0x57, 0xc0, 0xf1, 0xa2, 0x93, 0xbd, 0x8c, 0xdf, 0xee,
0x79, 0x48, 0x1b, 0x2a, 0xc1, 0xf0, 0xa3, 0x92, 0x5, 0x34, 0x67,
0x56, 0x78, 0x49, 0x1a, 0x2b, 0xbc, 0x8d, 0xde, 0xef, 0x82, 0xb3,
0xe0, 0xd1, 0x46, 0x77, 0x24, 0x15, 0x3b, 0xa, 0x59, 0x68, 0xff,
0xce, 0x9d, 0xac,
}
#endif // CONFIG_SHT4X_CRC_LOOKUP
/* Measurement times for the various precisions, in microseconds. */
static const uint16_t g_measurement_times[] =
{
[SHT4X_PREC_LOW] = 1600,
[SHT4X_PREC_MED] = 4500,
[SHT4X_PREC_HIGH] = 8300,
};
/* Commands for the various heating options. */
static const uint8_t g_heat_cmds[] =
{
[SHT4X_HEATER_200MW_1] = SHT4X_HEAT_200_1,
[SHT4X_HEATER_200MW_01] = SHT4X_HEAT_200_P1,
[SHT4X_HEATER_110MW_1] = SHT4X_HEAT_110_1,
[SHT4X_HEATER_110MW_01] = SHT4X_HEAT_110_P1,
[SHT4X_HEATER_20MW_1] = SHT4X_HEAT_20_1,
[SHT4X_HEATER_20MW_01] = SHT4X_HEAT_20_P1,
};
/* Timeouts for the various heating options in microseconds. */
static const uint32_t g_heat_times[] =
{
[SHT4X_HEATER_200MW_1] = 1000000, [SHT4X_HEATER_200MW_01] = 100000,
[SHT4X_HEATER_110MW_1] = 1000000, [SHT4X_HEATER_110MW_01] = 100000,
[SHT4X_HEATER_20MW_1] = 1000000, [SHT4X_HEATER_20MW_01] = 100000,
};
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
static int sht4x_open(FAR struct file *filep);
static int sht4x_close(FAR struct file *filep);
static ssize_t sht4x_write(FAR struct file *filep, FAR const char *buffer,
size_t buflen);
static ssize_t sht4x_read(FAR struct file *filep, FAR char *buffer,
size_t buflen);
static int sht4x_ioctl(FAR struct file *filep, int cmd, unsigned long arg);
static int sht4x_unlink(FAR struct inode *inode);
/****************************************************************************
* Private Data
****************************************************************************/
static const struct file_operations g_sht4xfops =
{
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
.open = sht4x_open,
.close = sht4x_close,
#else
.open = NULL,
.close = NULL,
#endif
.read = sht4x_read,
.write = sht4x_write,
.seek = NULL,
.ioctl = sht4x_ioctl,
.mmap = NULL,
.truncate = NULL,
.poll = NULL,
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
.unlink = sht4x_unlink,
#endif
};
/****************************************************************************
* Private Functions
****************************************************************************/
#ifdef CONFIG_SHT4X_CRC_LOOKUP
/****************************************************************************
* Name: sht4x_crc_lookup
*
* Description:
* Perform a CRC calculation using the lookup table.
*
****************************************************************************/
uint8_t sht4x_crc_lookup(const uint8_t *buf, uint8_t nbytes)
{
uint8_t crc = SHT4X_CRC_INIT;
for (uint8_t byte = 0; byte < nbytes; byte++)
{
crc = g_crc_lookup[crc ^ buf[byte]];
}
return crc;
}
#endif
/****************************************************************************
* Name: sht4x_crc_bitwise
*
* Description:
* Perform a CRC calculation using the bitwise calculation.
*
****************************************************************************/
uint8_t sht4x_crc_bitwise(const uint8_t *buf, uint8_t nbytes)
{
uint8_t crc = SHT4X_CRC_INIT;
for (uint8_t byte = 0; byte < nbytes; byte++)
{
crc ^= buf[byte];
for (uint8_t bit = 0; bit < 8; bit++)
{
if (crc & 0x80)
{
/* Discard the highest bit (implicit XOR), then divide by the
* polynomial.
*/
crc <<= 1;
crc ^= SHT4X_CRC_POLY;
}
else
{
/* Continue until the highest bit is set. */
crc <<= 1;
}
}
}
return crc;
}
/****************************************************************************
* Name: sht4x_crc
*
* Description:
* Perform a CRC calculation on the data to check for validity.
* The `buf` param must be a data buffer that ends with its own 8 bit CRC.
* The `nbytes` param is the length of the data including the 8 bit CRC.
*
****************************************************************************/
static int sht4x_crc(const uint8_t *buf, uint8_t nbytes)
{
#ifdef CONFIG_SHT4X_CRC_LOOKUP
if (sht4x_crc_lookup(buf, nbytes) != 0)
{
return -EBADMSG;
}
#else
if (sht4x_crc_bitwise(buf, nbytes) != 0)
{
return -EBADMSG;
}
#endif
return 0;
}
/****************************************************************************
* Name: sht4x_cmd
*
* Description:
* I2C access helper for sending commands to the SHT4x which receive data
* in response.
*
****************************************************************************/
static int sht4x_cmd(FAR struct sht4x_dev_s *priv, uint8_t command,
uint32_t timeout, uint16_t *data1, uint16_t *data2)
{
struct i2c_msg_s cmd;
struct i2c_msg_s read_data;
int err;
/* 2 byte data, 1 byte CRC, 2 byte data, 1 byte CRC. */
uint8_t combined_data[6];
cmd.frequency = CONFIG_SHT4X_I2C_FREQUENCY;
cmd.addr = priv->addr;
cmd.flags = 0;
cmd.buffer = &command;
cmd.length = sizeof(command);
/* Trigger measurement. */
err = I2C_TRANSFER(priv->i2c, &cmd, 1);
if (err < 0)
{
return err;
}
/* Wait for measurement to complete. Serial number command does not require
* wait time.
*/
if (timeout > 0)
{
usleep(timeout);
}
read_data.frequency = CONFIG_SHT4X_I2C_FREQUENCY;
read_data.addr = priv->addr;
read_data.flags = I2C_M_READ;
read_data.buffer = combined_data;
read_data.length = sizeof(combined_data);
err = I2C_TRANSFER(priv->i2c, &read_data, 1);
if (err < 0)
{
return err;
}
/* Check CRC for first data packet */
err = sht4x_crc(combined_data, 3);
if (err < 0)
{
return err;
}
/* Check CRC for second data packet */
err = sht4x_crc(combined_data + 3, 3);
if (err < 0)
{
return err;
}
*data1 = (uint16_t)(combined_data[0] << 8) | combined_data[1];
*data2 = (uint16_t)(combined_data[3] << 8) | combined_data[4];
return err;
}
/****************************************************************************
* Name: sht4x_reset
*
* Description:
* Perform a soft reset of the sensor. WARNING: Sensor is not available
* until 1ms after this command is sent.
*
****************************************************************************/
static int sht4x_reset(FAR struct sht4x_dev_s *priv)
{
struct i2c_msg_s msg[1];
uint8_t reset_cmd = SHT4X_SOFT_RESET;
msg[0].frequency = CONFIG_SHT4X_I2C_FREQUENCY;
msg[0].addr = priv->addr;
msg[0].flags = 0;
msg[0].buffer = &reset_cmd;
msg[0].length = sizeof(reset_cmd);
return I2C_TRANSFER(priv->i2c, msg, 1);
}
/****************************************************************************
* Name: sht4x_calc_temp
*
* Description:
* Calculate the temperature from the SHT4X raw data.
*
****************************************************************************/
static int32_t sht4x_calc_temp(uint16_t temp)
{
#ifdef CONFIG_SHT4X_FAHRENHEIT
/* Millidegrees Fahrenheit */
return -49000 + 315 * ((temp * 1000) / 65535);
#else
return -45000 + 175 * ((temp * 1000) / 65535); /* Millidegrees Celsius */
#endif // CONFIG_SHT4X_FAHRENHEIT
}
/****************************************************************************
* Name: sht4x_calc_hum
*
* Description:
* Calculate the humidity from the SHT4X raw data.
*
****************************************************************************/
static int16_t sht4x_calc_hum(uint16_t humidity)
{
int16_t hum = -600 + 125 * ((humidity * 100) / 65535); /* 0.01 %RH */
#ifdef CONFIG_SHT4X_LIMIT_HUMIDITY
/* Limit values of humidity, since values outside of 0-100 are invalid. */
if (hum < 0)
{
hum = 0;
}
else if (hum > 10000)
{
hum = 10000;
}
#endif // CONFIG_SHT4X_LIMIT_HUMIDITY
return hum;
}
/****************************************************************************
* 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: sht4x_open
*
* Description:
* This function is called whenever the SHT4X device is opened.
*
****************************************************************************/
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
static int sht4x_open(FAR struct file *filep)
{
FAR struct inode *inode = filep->f_inode;
FAR struct sht4x_dev_s *priv = inode->i_private;
int err;
err = nxmutex_lock(&priv->devlock);
if (err < 0)
{
return err;
}
/* Increment the count of open references on the driver */
priv->crefs++;
DEBUGASSERT(priv->crefs > 0);
nxmutex_unlock(&priv->devlock);
return 0;
}
#endif
/****************************************************************************
* Name: sht4x_close
*
* Description:
* This routine is called when the SHT4X device is closed.
*
****************************************************************************/
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
static int sht4x_close(FAR struct file *filep)
{
FAR struct inode *inode = filep->f_inode;
FAR struct sht4x_dev_s *priv = inode->i_private;
int err;
err = nxmutex_lock(&priv->devlock);
if (err < 0)
{
return err;
}
/* 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 0;
}
nxmutex_unlock(&priv->devlock);
return 0;
}
#endif
/****************************************************************************
* Name: sht4x_read
*
* Description:
* Character driver interface to sensor for debugging.
*
****************************************************************************/
static ssize_t sht4x_read(FAR struct file *filep, FAR char *buffer,
size_t buflen)
{
FAR struct inode *inode = filep->f_inode;
FAR struct sht4x_dev_s *priv = inode->i_private;
ssize_t length = 0;
struct sht4x_raw_data_s raw_data;
struct sht4x_conv_data_s data;
int err;
/* If file position is non-zero, then we're at the end of file. */
if (filep->f_pos > 0) return 0;
/* Get exclusive access */
err = nxmutex_lock(&priv->devlock);
if (err < 0)
{
return err;
}
#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 0;
}
#endif
err = sht4x_cmd(priv, g_precision_read[priv->precision],
g_measurement_times[priv->precision], &raw_data.raw_temp,
&raw_data.raw_hum);
if (err < 0)
{
#ifdef CONFIG_SHT4X_DEBUG
sht4x_dbg("Could not read device: %d\n", err);
#endif // CONFIG_SHT4X_DEBUG
nxmutex_unlock(&priv->devlock);
return err;
}
/* Convert to proper units. */
data.temp = sht4x_calc_temp(raw_data.raw_temp);
data.hum = sht4x_calc_hum(raw_data.raw_hum);
length = snprintf(buffer, buflen, "%ld m" SHT4X_TEMP_UNIT ", %d %%RH\n",
data.temp, data.hum / 100);
if (length > buflen) length = buflen;
filep->f_pos += length;
nxmutex_unlock(&priv->devlock);
return length;
}
/****************************************************************************
* Name: sht4x_write
*
* Description:
* Not implemented.
****************************************************************************/
static ssize_t sht4x_write(FAR struct file *filep, FAR const char *buffer,
size_t buflen)
{
return -ENOSYS;
}
/****************************************************************************
* Name: sht4x_ioctl
****************************************************************************/
static int sht4x_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
{
FAR struct inode *inode = filep->f_inode;
FAR struct sht4x_dev_s *priv = inode->i_private;
int err;
err = nxmutex_lock(&priv->devlock);
if (err < 0)
{
return err;
}
#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)
{
case SNIOC_RESET:
err = sht4x_reset(priv);
break;
case SNIOC_WHO_AM_I:
{
union sht4x_serialno_t serialno;
err = sht4x_cmd(priv, SHT4X_READ_SERIAL, 10, &serialno.halves.msb,
&serialno.halves.lsb);
*((uint32_t *)(arg)) = serialno.full;
}
break;
case SNIOC_READ_RAW_DATA:
err = sht4x_cmd(priv, g_precision_read[priv->precision],
g_measurement_times[priv->precision],
&((struct sht4x_raw_data_s *)(arg))->raw_temp,
&((struct sht4x_raw_data_s *)(arg))->raw_hum);
break;
case SNIOC_MEASURE:
case SNIOC_READ_CONVERT_DATA:
{
uint16_t raw_t;
uint16_t raw_h;
err = sht4x_cmd(priv, g_precision_read[priv->precision],
g_measurement_times[priv->precision],
&raw_t, &raw_h);
((struct sht4x_conv_data_s *)(arg))->temp = sht4x_calc_temp(raw_t);
((struct sht4x_conv_data_s *)(arg))->hum = sht4x_calc_hum(raw_h);
}
break;
case SNIOC_HEAT:
{
struct timespec now;
clock_systime_timespec(&now);
/* Check if it has been one second since the last heat command. */
if (!has_time_passed(now, priv->last_heat, 1))
{
err = -EAGAIN; /* Signal to try again in some time. */
break;
}
/* Caller must pass heater option in the temperature argument. */
uint16_t raw_t = ((struct sht4x_conv_data_s *)(arg))->temp;
uint16_t raw_h;
err = sht4x_cmd(priv, g_heat_cmds[raw_t], g_heat_times[raw_t],
&raw_t, &raw_h);
((struct sht4x_conv_data_s *)(arg))->temp = sht4x_calc_temp(raw_t);
((struct sht4x_conv_data_s *)(arg))->hum = sht4x_calc_hum(raw_h);
clock_systime_timespec(&priv->last_heat); /* Update last heat time. */
}
break;
case SNIOC_CONFIGURE:
/* Caller must pass precision option as argument. */
priv->precision = arg;
#ifdef CONFIG_SHT4X_DEBUG
sht4x_dbg("Precision set to %d\n", priv->precision);
#endif // CONFIG_SHT4X_DEBUG
break;
default:
err = -EINVAL;
break;
}
nxmutex_unlock(&priv->devlock);
return err;
}
/****************************************************************************
* Name: sht4x_unlink
****************************************************************************/
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
static int sht4x_unlink(FAR struct inode *inode)
{
FAR struct sht4x_dev_s *priv;
int err;
DEBUGASSERT(inode->i_private != NULL);
priv = inode->i_private;
err = nxmutex_lock(&priv->devlock);
if (err < 0)
{
return err;
}
/* Are there open references to the driver data structure? */
if (priv->crefs <= 0)
{
nxmutex_destroy(&priv->devlock);
kmm_free(priv);
return 0;
}
/* 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
****************************************************************************/
/****************************************************************************
* Name: sht4x_register
*
* Description:
* Register the SHT4X 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 with
* the SHT4X
* addr - The I2C address of the SHT4X. The I2C address is one of 0x44,
*0x45 and 0x46.
*
* Returned Value:
* Zero (OK) on success; a negated errno value on failure.
*
****************************************************************************/
int sht4x_register(FAR const char *devpath, FAR struct i2c_master_s *i2c,
uint8_t addr)
{
FAR struct sht4x_dev_s *priv;
int err;
DEBUGASSERT(i2c != NULL);
DEBUGASSERT(addr == 0x44 || addr == 0x45 || addr == 0x46);
/* Initialize the device structure */
priv = kmm_zalloc(sizeof(struct sht4x_dev_s));
if (priv == NULL)
{
snerr("ERROR: Failed to allocate instance.\n");
return -ENOMEM;
}
priv->i2c = i2c;
priv->addr = addr;
priv->precision = SHT4X_PREC_HIGH;
err = clock_systime_timespec(&priv->last_heat);
if (err < 0)
{
snerr("ERROR: Failed to get timespec: %d\n", err);
kmm_free(priv);
return err;
}
/* Allow heat immediately after registration since in theory the sensor has
* never had its heater activated yet.
*/
priv->last_heat.tv_sec -= 1;
err = nxmutex_init(&priv->devlock);
if (err < 0)
{
snerr("ERROR: Failed to register SHT4X driver: %d\n", err);
kmm_free(priv);
return err;
}
/* Register the character driver */
err = register_driver(devpath, &g_sht4xfops, 0666, priv);
if (err < 0)
{
snerr("ERROR: Failed to register SHT4X driver: %d\n", err);
nxmutex_destroy(&priv->devlock);
kmm_free(priv);
}
return err;
}
#endif /* CONFIG_I2C && CONFIG_SENSORS_SHT4X */
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