/****************************************************************************
* drivers/sensors/sht21.c
* Driver for the Sensirion SHT20 and SHT21 temperature and humidity sensors
*
* Copyright (C) 2018 Haltian Ltd. All rights reserved.
* Author: Juha Niskanen <juha.niskanen@haltian.com>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <stdio.h>
#include <errno.h>
#include <debug.h>
#include <time.h>
#include <nuttx/kmalloc.h>
#include <nuttx/fs/fs.h>
#include <nuttx/i2c/i2c_master.h>
#include <nuttx/sensors/sht21.h>
#include <nuttx/random.h>
#if defined(CONFIG_I2C) && defined(CONFIG_SENSORS_SHT21)
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
#ifdef CONFIG_SHT21_DEBUG
# define sht21_dbg(x, ...) _info(x, ##__VA_ARGS__)
#else
# define sht21_dbg(x, ...) sninfo(x, ##__VA_ARGS__)
#endif
#ifndef CONFIG_SHT21_I2C_FREQUENCY
# define CONFIG_SHT21_I2C_FREQUENCY 400000
#endif
/* I2C command bytes */
#define SHT21_TRIG_T_MEAS_HM 0xe3
#define SHT21_TRIG_RH_MEAS_HM 0xe5
#define SHT21_WRITE_USERREG 0xe6
#define SHT21_READ_USERREG 0xe7
#define SHT21_SOFT_RESET 0xfe
/****************************************************************************
* Private
****************************************************************************/
struct sht21_dev_s
{
FAR struct i2c_master_s *i2c; /* I2C interface */
uint8_t addr; /* I2C address */
bool valid; /* If cached readings are valid */
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
bool unlinked; /* True, driver has been unlinked */
#endif
struct timespec last_update; /* Last time when sensor was read */
int temperature; /* Cached temperature */
int humidity; /* Cached humidity */
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
int16_t crefs; /* Number of open references */
#endif
sem_t devsem;
};
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
/* I2C Helpers */
static int sht21_access(FAR struct sht21_dev_s *priv,
uint8_t reg_addr, bool read,
FAR uint8_t *reg_value, uint8_t len);
#ifdef CONFIG_SHT21_DEBUG
static int sht21_read8(FAR struct sht21_dev_s *priv, uint8_t regaddr,
FAR uint8_t *regvalue);
#endif
static int sht21_read16(FAR struct sht21_dev_s *priv, uint8_t regaddr,
FAR uint16_t *regvalue);
/* Character driver methods */
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
static int sht21_open(FAR struct file *filep);
static int sht21_close(FAR struct file *filep);
#endif
static ssize_t sht21_read(FAR struct file *filep, FAR char *buffer,
size_t buflen);
static ssize_t sht21_write(FAR struct file *filep, FAR const char *buffer,
size_t buflen);
static int sht21_ioctl(FAR struct file *filep, int cmd,
unsigned long arg);
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
static int sht21_unlink(FAR struct inode *inode);
#endif
/****************************************************************************
* Private Data
****************************************************************************/
static const struct file_operations g_sht21fops =
{
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
sht21_open, /* open */
sht21_close, /* close */
#else
NULL, /* open */
NULL, /* close */
#endif
sht21_read, /* read */
sht21_write, /* write */
NULL, /* seek */
sht21_ioctl, /* ioctl */
NULL /* poll */
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
, sht21_unlink /* unlink */
#endif
};
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: sht21_access
*
* Description:
* I2C access helper.
*
****************************************************************************/
static int sht21_access(FAR struct sht21_dev_s *priv,
uint8_t reg_addr, bool read,
FAR uint8_t *reg_value, uint8_t len)
{
struct i2c_msg_s msg[2];
int ret;
msg[0].frequency = CONFIG_SHT21_I2C_FREQUENCY;
msg[0].addr = priv->addr;
msg[0].flags = 0;
msg[0].buffer = ®_addr;
msg[0].length = 1;
msg[1].frequency = CONFIG_SHT21_I2C_FREQUENCY;
msg[1].addr = priv->addr;
msg[1].flags = read ? I2C_M_READ : I2C_M_NOSTART;
msg[1].buffer = reg_value;
msg[1].length = len;
ret = I2C_TRANSFER(priv->i2c, msg, (len > 0) ? 2 : 1);
sht21_dbg("reg_addr: 0x%02X len: %d reg_value: 0x%02x ret: %d\n",
reg_addr, len, reg_value ? *reg_value : 0, ret);
return (ret >= 0) ? OK : ret;
}
/****************************************************************************
* Name: sht21_read8
*
* Description:
* Read 8-bit value from the I2C device.
*
****************************************************************************/
#ifdef CONFIG_SHT21_DEBUG
static int sht21_read8(FAR struct sht21_dev_s *priv, uint8_t regaddr,
FAR uint8_t *regvalue)
{
uint8_t buf[1];
int ret;
ret = sht21_access(priv, regaddr, true, buf, 1);
if (ret == 0)
{
*regvalue = buf[0];
}
return ret;
}
#endif
/****************************************************************************
* Name: sht21_read16
*
* Description:
* Read 16-bit value from the I2C device (MSB first).
*
****************************************************************************/
static int sht21_read16(FAR struct sht21_dev_s *priv, uint8_t regaddr,
FAR uint16_t *regvalue)
{
uint8_t buf[2];
int ret;
ret = sht21_access(priv, regaddr, true, buf, 2);
if (ret == 0)
{
*regvalue = ((uint16_t)buf[0] << 8) | (uint16_t)buf[1];
}
return ret;
}
/****************************************************************************
* Name: sht21_softreset
*
* Description:
* Reset the SHT2x sensor. This takes less than 15 ms.
*
****************************************************************************/
static inline int sht21_softreset(FAR struct sht21_dev_s *priv)
{
return sht21_access(priv, SHT21_SOFT_RESET, false, NULL, 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: sht21_temp_to_mcelsius
*
* Description:
* Convert raw temperature value to milli celsius.
*
****************************************************************************/
static inline int sht21_temp_to_mcelsius(int raw)
{
/* Clear status bits. */
raw &= ~0x03;
/* Formula T = -46.85 + 175.72 * ST / 2^16 from datasheet 6.2,
* converted to integer fixed point (3 digits) representation.
*/
return (((175720 >> 3) * raw) >> 13) - 46850;
}
/****************************************************************************
* Name: sht21_rh_to_pcm
*
* Description:
* Convert raw humidity value to one-thousandths of a percent
* (per cent mille) relative humidity.
*
****************************************************************************/
static inline int sht21_rh_to_pcm(int raw)
{
/* Clear status bits. */
raw &= ~0x03;
/* Formula RH = -6.0 + 125.0 * SRH / 2^16 from datasheet 6.1,
* converted to integer fixed point (3 digits) representation.
*/
return (((125000 >> 3) * raw) >> 13) - 6000;
}
/****************************************************************************
* Name: sht21_read_values
*
* Description:
*
****************************************************************************/
static int sht21_read_values(FAR struct sht21_dev_s *priv, FAR int *temp,
FAR int *rh)
{
uint16_t temp16;
uint16_t rh16;
struct timespec ts;
int ret;
clock_gettime(CLOCK_REALTIME, &ts);
/* Datasheet section 2.3: "To keep self heating below 0.1°C, SHT2x
* should not be active for more than 10% of the time – e.g. maximum
* two measurements per second at 12bit accuracy shall be made."
* We limit to one measurement per second to keep arithmetic simple.
*/
if (!priv->valid || has_time_passed(ts, priv->last_update, 1))
{
/* Read the raw temperature data */
ret = sht21_read16(priv, SHT21_TRIG_T_MEAS_HM, &temp16);
if (ret < 0)
{
snerr("ERROR: sht21_read16 failed: %d\n", ret);
return ret;
}
/* Read the raw humidity data */
ret = sht21_read16(priv, SHT21_TRIG_RH_MEAS_HM, &rh16);
if (ret < 0)
{
snerr("ERROR: sht21_read16 failed: %d\n", ret);
return ret;
}
add_sensor_randomness(ts.tv_nsec ^ ((int)temp16 << 16 | rh16));
priv->temperature = sht21_temp_to_mcelsius(temp16);
priv->humidity = sht21_rh_to_pcm(rh16);
priv->last_update = ts;
priv->valid = true;
}
*temp = priv->temperature;
*rh = priv->humidity;
return OK;
}
/****************************************************************************
* Name: sht21_open
*
* Description:
* This function is called whenever the SHT2x device is opened.
*
****************************************************************************/
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
static int sht21_open(FAR struct file *filep)
{
FAR struct inode *inode = filep->f_inode;
FAR struct sht21_dev_s *priv = inode->i_private;
int ret;
/* Get exclusive access */
do
{
ret = nxsem_wait(&priv->devsem);
/* The only case that an error should occur here is if the wait was
* awakened by a signal.
*/
DEBUGASSERT(ret == OK || ret == -EINTR);
}
while (ret == -EINTR);
/* Increment the count of open references on the driver */
priv->crefs++;
DEBUGASSERT(priv->crefs > 0);
nxsem_post(&priv->devsem);
return OK;
}
#endif
/****************************************************************************
* Name: sht21_close
*
* Description:
* This routine is called when the SHT2x device is closed.
*
****************************************************************************/
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
static int sht21_close(FAR struct file *filep)
{
FAR struct inode *inode = filep->f_inode;
FAR struct sht21_dev_s *priv = inode->i_private;
int ret;
/* Get exclusive access */
do
{
ret = nxsem_wait(&priv->devsem);
/* The only case that an error should occur here is if the wait was
* awakened by a signal.
*/
DEBUGASSERT(ret == OK || ret == -EINTR);
}
while (ret == -EINTR);
/* 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)
{
nxsem_destroy(&priv->devsem);
kmm_free(priv);
return OK;
}
nxsem_post(&priv->devsem);
return OK;
}
#endif
/****************************************************************************
* Name: sht21_read
****************************************************************************/
static ssize_t sht21_read(FAR struct file *filep, FAR char *buffer, size_t buflen)
{
FAR struct inode *inode = filep->f_inode;
FAR struct sht21_dev_s *priv = inode->i_private;
ssize_t length = 0;
int temp;
int rh;
int ret;
/* Get exclusive access */
do
{
ret = nxsem_wait(&priv->devsem);
/* The only case that an error should occur here is if the wait was
* awakened by a signal.
*/
DEBUGASSERT(ret == OK || ret == -EINTR);
}
while (ret == -EINTR);
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
if (priv->unlinked)
{
/* Do not allow operations on unlinked sensors. This allows
* sensor use on hot swappable I2C bus.
*/
nxsem_post(&priv->devsem);
return -ENODEV;
}
#endif
ret = sht21_read_values(priv, &temp, &rh);
if (ret < 0)
{
sht21_dbg("cannot read data: %d\n", ret);
}
else
{
/* This interface is mainly intended for easy debugging in nsh. */
length = snprintf(buffer, buflen, "%d %d\n", temp, rh);
if (length > buflen)
{
length = buflen;
}
}
nxsem_post(&priv->devsem);
return length;
}
/****************************************************************************
* Name: sht21_write
****************************************************************************/
static ssize_t sht21_write(FAR struct file *filep, FAR const char *buffer,
size_t buflen)
{
return -ENOSYS;
}
/****************************************************************************
* Name: sht21_ioctl
****************************************************************************/
static int sht21_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
{
FAR struct inode *inode = filep->f_inode;
FAR struct sht21_dev_s *priv = inode->i_private;
int ret;
/* Get exclusive access */
do
{
ret = nxsem_wait(&priv->devsem);
/* The only case that an error should occur here is if the wait was
* awakened by a signal.
*/
DEBUGASSERT(ret == OK || ret == -EINTR);
}
while (ret == -EINTR);
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
if (priv->unlinked)
{
/* Do not allow operations on unlinked sensors. This allows
* sensor use on hot swappable I2C bus.
*/
nxsem_post(&priv->devsem);
return -ENODEV;
}
#endif
switch (cmd)
{
/* Soft reset the SHT2x, Arg: None */
case SNIOC_RESET:
{
ret = sht21_softreset(priv);
sht21_dbg("softreset ret: %d\n", ret);
}
break;
case SNIOC_READ_RAW_DATA:
case SNIOC_READ_CONVERT_DATA:
{
int temp;
int rh;
ret = sht21_read_values(priv, &temp, &rh);
if (ret < 0)
{
sht21_dbg("cannot read data: %d\n", ret);
}
else
{
FAR struct sht21_conv_data_s *data =
(FAR struct sht21_conv_data_s *)arg;
data->temperature = temp;
data->humidity = rh;
}
}
break;
#ifdef CONFIG_SHT21_DEBUG
case SNIOC_DUMP_REGS:
{
uint8_t userreg = 0;
ret = sht21_read8(priv, SHT21_READ_USERREG, &userreg);
sht21_dbg("read8 ret = %d, userreg = %d\n", ret, userreg);
}
break;
#endif
default:
sht21_dbg("Unrecognized cmd: %d\n", cmd);
ret = -ENOTTY;
break;
}
nxsem_post(&priv->devsem);
return ret;
}
/****************************************************************************
* Name: sht21_unlink
****************************************************************************/
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
static int sht21_unlink(FAR struct inode *inode)
{
FAR struct sht21_dev_s *priv;
int ret;
DEBUGASSERT(inode != NULL && inode->i_private != NULL);
priv = (FAR struct sht21_dev_s *)inode->i_private;
/* Get exclusive access */
do
{
ret = nxsem_wait(&priv->devsem);
/* The only case that an error should occur here is if the wait was
* awakened by a signal.
*/
DEBUGASSERT(ret == OK || ret == -EINTR);
}
while (ret == -EINTR);
/* Are there open references to the driver data structure? */
if (priv->crefs <= 0)
{
nxsem_destroy(&priv->devsem);
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;
nxsem_post(&priv->devsem);
return ret;
}
#endif
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: sht21_register
*
* Description:
* Register the SHT2x 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 SHT2x
* addr - The I2C address of the SHT2x. The I2C address of both SHT20
* and SHT21 is always 0x40.
*
* Returned Value:
* Zero (OK) on success; a negated errno value on failure.
*
****************************************************************************/
int sht21_register(FAR const char *devpath, FAR struct i2c_master_s *i2c,
uint8_t addr)
{
FAR struct sht21_dev_s *priv;
int ret;
DEBUGASSERT(i2c != NULL);
DEBUGASSERT(addr == CONFIG_SHT21_ADDR);
/* Initialize the device structure */
priv = (FAR struct sht21_dev_s *)kmm_zalloc(sizeof(struct sht21_dev_s));
if (priv == NULL)
{
snerr("ERROR: Failed to allocate instance\n");
return -ENOMEM;
}
priv->i2c = i2c;
priv->addr = addr;
nxsem_init(&priv->devsem, 0, 1);
/* Register the character driver */
ret = register_driver(devpath, &g_sht21fops, 0666, priv);
if (ret < 0)
{
snerr("ERROR: Failed to register driver: %d\n", ret);
kmm_free(priv);
}
return ret;
}
#endif /* CONFIG_I2C && CONFIG_SENSORS_SHT21 */