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incubator-nuttx/drivers/sensors/dhtxx.c

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/****************************************************************************
* drivers/sensors/dhtxx.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 <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <debug.h>
#include <nuttx/kmalloc.h>
#include <nuttx/fs/fs.h>
#include <nuttx/signal.h>
#include <nuttx/clock.h>
#include <nuttx/mutex.h>
#include <nuttx/sensors/dhtxx.h>
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
#define DHTXX_START_SIGNAL_LOW_US 20000
#define DHTXX_START_SIGNAL_HIGH_US 100
#define DHTXX_RESPONSE_SIGNAL_US 85
#define DHTXX_TRANSMISSION_START_US 55
#define DHTXX_MIN_ZERO_DURATION 22
#define DHTXX_MAX_ZERO_DURATION 30
#define DHTXX_MIN_ONE_DURATION 40
#define DHTXX_MAX_ONE_DURATION 75
#define DHTXX_SAMPLING_PERIOD_S 2
#define DHTXX_RESPONSE_BITS 40U
#define DHT11_MIN_HUM 20.0F
#define DHT11_MAX_HUM 90.0F
#define DHT11_MIN_TEMP 0.0F
#define DHT11_MAX_TEMP 50.0F
#define DHT12_MIN_HUM 20.0F
#define DHT12_MAX_HUM 95.0F
#define DHT12_MIN_TEMP -20.0F
#define DHT12_MAX_TEMP 60.0F
#define DHT22_MIN_HUM 0.0F
#define DHT22_MAX_HUM 100.0F
#define DHT22_MIN_TEMP -40.0F
#define DHT22_MAX_TEMP 80.0F
/****************************************************************************
* Private Type Definitions
****************************************************************************/
struct dhtxx_dev_s
{
FAR struct dhtxx_config_s *config;
mutex_t devlock;
uint8_t raw_data[5];
};
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
static void dht_standby_mode(FAR struct dhtxx_dev_s *priv);
static void dht_send_start_signal(FAR struct dhtxx_dev_s *priv);
static int dht_prepare_reading(FAR struct dhtxx_dev_s *priv);
static int dht_read_raw_data(FAR struct dhtxx_dev_s *priv);
static bool dht_verify_checksum(FAR struct dhtxx_dev_s *priv);
static bool dht_check_data(FAR struct dhtxx_sensor_data_s *data,
float min_hum, float max_hum,
float min_temp, float max_temp);
static int dht_parse_data(FAR struct dhtxx_dev_s *priv,
FAR struct dhtxx_sensor_data_s *data);
/* Character driver methods */
static int dhtxx_open(FAR struct file *filep);
static ssize_t dhtxx_read(FAR struct file *filep, FAR char *buffer,
size_t buflen);
static ssize_t dhtxx_write(FAR struct file *filep, FAR const char *buffer,
size_t buflen);
/****************************************************************************
* Private Data
****************************************************************************/
static const struct file_operations g_dhtxxfops =
{
dhtxx_open, /* open */
NULL, /* close */
dhtxx_read, /* read */
dhtxx_write, /* write */
};
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: dht_standby_mode
*
* Description:
* Put the sensor in low power consumption (standby) mode.
*
****************************************************************************/
static void dht_standby_mode(FAR struct dhtxx_dev_s *priv)
{
priv->config->config_data_pin(priv->config, false);
priv->config->set_data_pin(priv->config, true);
}
/****************************************************************************
* Name: dht_send_start_signal
*
* Description:
* Send a start signal to the sensor.
*
****************************************************************************/
static void dht_send_start_signal(FAR struct dhtxx_dev_s *priv)
{
int64_t start_time;
int64_t current_time;
priv->config->config_data_pin(priv->config, false);
priv->config->set_data_pin(priv->config, false);
start_time = priv->config->get_clock(priv->config);
while (1)
{
current_time = priv->config->get_clock(priv->config);
if (current_time - start_time >= DHTXX_START_SIGNAL_LOW_US)
{
break;
}
}
priv->config->set_data_pin(priv->config, true);
start_time = priv->config->get_clock(priv->config);
while (1)
{
current_time = priv->config->get_clock(priv->config);
if (current_time - start_time >= DHTXX_START_SIGNAL_HIGH_US)
{
break;
}
}
}
/****************************************************************************
* Name: dht_prepare_reading
*
* Description:
* Gets the sensor ready for transmitting data.
*
****************************************************************************/
static int dht_prepare_reading(FAR struct dhtxx_dev_s *priv)
{
int64_t start_time;
int64_t current_time;
/* Prepare for reading data. */
priv->config->config_data_pin(priv->config, true);
/* The DHT will clear the data pin for about 80uS. */
start_time = priv->config->get_clock(priv->config);
while (!priv->config->read_data_pin(priv->config))
{
current_time = priv->config->get_clock(priv->config);
if (current_time - start_time > DHTXX_RESPONSE_SIGNAL_US)
{
return -1;
}
}
/* The DHT will set the data pin for about 80uS. */
while (priv->config->read_data_pin(priv->config))
{
current_time = priv->config->get_clock(priv->config);
if (current_time - start_time > DHTXX_RESPONSE_SIGNAL_US)
{
return -1;
}
}
return 0;
}
/****************************************************************************
* Name: dht_read_raw_data
*
* Description:
* Reads raw data from the sensor.
*
****************************************************************************/
static int dht_read_raw_data(FAR struct dhtxx_dev_s *priv)
{
int64_t start_time;
int64_t end_time;
int64_t current_time;
uint8_t i;
uint8_t j;
j = 0u;
for (i = 0u; i < DHTXX_RESPONSE_BITS; i++)
{
/* Start of transmission begins with a ~50uS low. */
start_time = priv->config->get_clock(priv->config);
while (!priv->config->read_data_pin(priv->config))
{
current_time = priv->config->get_clock(priv->config);
if (current_time - start_time > DHTXX_TRANSMISSION_START_US)
{
return -1;
}
}
/* Get start time. */
start_time = priv->config->get_clock(priv->config);
while (priv->config->read_data_pin(priv->config))
{
current_time = priv->config->get_clock(priv->config);
if (current_time - start_time > DHTXX_MAX_ONE_DURATION)
{
return -1;
}
}
end_time = priv->config->get_clock(priv->config);
if (end_time - start_time >= DHTXX_MIN_ONE_DURATION)
{
priv->raw_data[j] = (priv->raw_data[j] << 1U) | 1U;
}
else
{
priv->raw_data[j] = priv->raw_data[j] << 1U;
}
if (i % 8U == 7U)
{
j++;
}
}
return 0;
}
/****************************************************************************
* Name: dht_verify_checksum
*
* Description:
* Verify the sent checksum with the calculated checksum.
*
****************************************************************************/
static bool dht_verify_checksum(FAR struct dhtxx_dev_s *priv)
{
uint8_t sum;
sum = (priv->raw_data[0] + priv->raw_data[1] +
priv->raw_data[2] + priv->raw_data[3]) & 0xffu;
return (sum == priv->raw_data[4]);
}
/****************************************************************************
* Name: dht_check_data
*
* Description:
* Check for data integrity in regards with the sensors range.
*
****************************************************************************/
static bool dht_check_data(FAR struct dhtxx_sensor_data_s *data,
float min_hum, float max_hum,
float min_temp, float max_temp)
{
if (data->hum < min_hum || data->hum > max_hum)
{
return false;
}
if (data->temp < min_temp || data->temp > max_temp)
{
return false;
}
return true;
}
/****************************************************************************
* Name: dht_check_data
*
* Description:
* Get the humidity and temperature's values from raw data.
*
****************************************************************************/
static int dht_parse_data(FAR struct dhtxx_dev_s *priv,
FAR struct dhtxx_sensor_data_s *data)
{
int ret = OK;
switch (priv->config->type)
{
case DHTXX_DHT11:
data->hum = priv->raw_data[0];
data->temp = priv->raw_data[2];
/* if data is not within sensor's measurement range,
* an error must have occurred.
*/
if (!dht_check_data(data, DHT11_MIN_HUM, DHT11_MAX_HUM,
DHT11_MIN_TEMP, DHT11_MAX_TEMP))
{
ret = -1;
}
break;
case DHTXX_DHT12:
data->hum = priv->raw_data[0] + priv->raw_data[1] * 0.1F;
data->temp = priv->raw_data[2] + (priv->raw_data[3] & 0x7fu) * 0.1F;
if (priv->raw_data[3] & 0x80u)
{
data->temp *= -1;
}
if (!dht_check_data(data, DHT12_MIN_HUM, DHT12_MAX_HUM,
DHT12_MIN_TEMP, DHT12_MAX_TEMP))
{
ret = -1;
}
break;
case DHTXX_DHT21:
case DHTXX_DHT22:
case DHTXX_DHT33:
case DHTXX_DHT44:
data->hum = (priv->raw_data[0] << 8u | priv->raw_data[1]) * 0.1F;
data->temp = (((priv->raw_data[2] & 0x7fu) << 8u) |
priv->raw_data[3]) * 0.1F;
if (priv->raw_data[2] & 0x80u)
{
data->temp *= -1;
}
if (!dht_check_data(data, DHT22_MIN_HUM, DHT22_MAX_HUM,
DHT22_MIN_TEMP, DHT22_MAX_TEMP))
{
ret = -1;
}
break;
}
return ret;
}
/****************************************************************************
* Name: dhtxx_open
*
* Description:
* This function is called whenever the Dhtxx device is opened.
*
****************************************************************************/
static int dhtxx_open(FAR struct file *filep)
{
FAR struct inode *inode = filep->f_inode;
FAR struct dhtxx_dev_s *priv = inode->i_private;
int ret;
/* Acquire the mutex, wait the sampling time before sending anything to
* pass unstable state.
*/
ret = nxmutex_lock(&priv->devlock);
if (ret < 0)
{
return ret;
}
dht_standby_mode(priv);
nxsig_sleep(DHTXX_SAMPLING_PERIOD_S);
/* Sensor ready. */
nxmutex_unlock(&priv->devlock);
return OK;
}
/****************************************************************************
* Name: dhtxx_read
****************************************************************************/
static ssize_t dhtxx_read(FAR struct file *filep, FAR char *buffer,
size_t buflen)
{
int ret = OK;
FAR struct inode *inode = filep->f_inode;
FAR struct dhtxx_dev_s *priv = inode->i_private;
FAR struct dhtxx_sensor_data_s *data =
(FAR struct dhtxx_sensor_data_s *)buffer;
if (!buffer)
{
snerr("ERROR: Buffer is null.\n");
return -1;
}
if (buflen < sizeof(FAR struct dhtxx_sensor_data_s))
{
snerr("ERROR: Not enough memory to read data sample.\n");
return -ENOSYS;
}
memset(priv->raw_data, 0u, sizeof(priv->raw_data));
ret = nxmutex_lock(&priv->devlock);
if (ret < 0)
{
return (ssize_t)ret;
}
dht_send_start_signal(priv);
if (dht_prepare_reading(priv) != 0)
{
data->status = DHTXX_TIMEOUT;
ret = -1;
goto out;
}
if (dht_read_raw_data(priv) != 0)
{
data->status = DHTXX_TIMEOUT;
ret = -1;
goto out;
}
if (!dht_verify_checksum(priv))
{
data->status = DHTXX_CHECKSUM_ERROR;
ret = -1;
goto out;
}
if (dht_parse_data(priv, data) != 0)
{
data->status = DHTXX_READ_ERROR;
ret = -1;
}
else
{
data->status = DHTXX_SUCCESS;
}
out:
/* Done reading, set the sensor back to low mode. */
dht_standby_mode(priv);
/* Don't release the semaphore just yet. The sensor needs time between
* consecutive readings.
*/
nxsig_sleep(DHTXX_SAMPLING_PERIOD_S);
/* Sensor ready for new reading */
nxmutex_unlock(&priv->devlock);
return ret;
}
/****************************************************************************
* Name: dhtxx_write
****************************************************************************/
static ssize_t dhtxx_write(FAR struct file *filep, FAR const char *buffer,
size_t buflen)
{
return -ENOSYS;
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: dhtxx_register
*
* Description:
* Register the Dhtxx character device as 'devpath'
*
* Input Parameters:
* devpath - The full path to the driver to register. E.g., "/dev/dht0"
*
* Returned Value:
* Zero (OK) on success; a negated errno value on failure.
*
****************************************************************************/
int dhtxx_register(FAR const char *devpath,
FAR struct dhtxx_config_s *config)
{
FAR struct dhtxx_dev_s *priv;
int ret;
/* Initialize the Dhtxx device structure */
priv = kmm_malloc(sizeof(struct dhtxx_dev_s));
if (priv == NULL)
{
snerr("ERROR: Failed to allocate instance\n");
return -ENOMEM;
}
priv->config = config;
nxmutex_init(&priv->devlock);
/* Register the character driver */
ret = register_driver(devpath, &g_dhtxxfops, 0666, priv);
if (ret < 0)
{
nxmutex_destroy(&priv->devlock);
kmm_free(priv);
snerr("ERROR: Failed to register driver: %d\n", ret);
}
return ret;
}
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