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pkarashchenko pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/incubator-nuttx.git
commit bf332cf888349b102f85665900afbaa46d5b56bd
Author: SPRESENSE <41312067+sprese...@users.noreply.github.com>
AuthorDate: Mon Apr 11 16:30:13 2022 +0900
drivers/sensors: Add new driver for scd41 sensor module
Add Sensirion's SCD41 CO2, temperature and humidity sensor driver.
---
drivers/sensors/Kconfig | 31 ++
drivers/sensors/Make.defs | 4 +
drivers/sensors/scd41.c | 1030 +++++++++++++++++++++++++++++++++++++++++
include/nuttx/sensors/scd41.h | 75 +++
4 files changed, 1140 insertions(+)
diff --git a/drivers/sensors/Kconfig b/drivers/sensors/Kconfig
index 38b77f8183..07ef718430 100644
--- a/drivers/sensors/Kconfig
+++ b/drivers/sensors/Kconfig
@@ -845,6 +845,37 @@ config SCD30_DEBUG
endif # SENSORS_SCD30
+config SENSORS_SCD41
+ bool "Sensirion SCD41 CO2, humidity and temperature sensor"
+ default n
+ ---help---
+ Enable driver support for the Sensirion SCD41 CO₂, humidity and
+ temperature sensor.
+
+if SENSORS_SCD41
+
+config SCD41_I2C
+ bool "Sensirion SCD41 I2C mode"
+ default y
+ select I2C
+
+config SCD41_I2C_FREQUENCY
+ int "SCD41 I2C frequency"
+ default 100000
+ range 1 100000
+ depends on SCD41_I2C
+ ---help---
+ I2C frequency for SCD41. Note, maximum supported frequency for
+ this sensor is 100kHz.
+
+config SCD41_DEBUG
+ bool "Debug support for the SCD41"
+ default n
+ ---help---
+ Enables debug features for the SCD41
+
+endif # SENSORS_SCD41
+
config SENSORS_SGP30
bool "Sensirion SGP30 Gas Platform sensor"
default n
diff --git a/drivers/sensors/Make.defs b/drivers/sensors/Make.defs
index 96e0d59307..54e87e46a5 100644
--- a/drivers/sensors/Make.defs
+++ b/drivers/sensors/Make.defs
@@ -192,6 +192,10 @@ ifeq ($(CONFIG_SENSORS_SCD30),y)
CSRCS += scd30.c
endif
+ifeq ($(CONFIG_SENSORS_SCD41),y)
+ CSRCS += scd41.c
+endif
+
ifeq ($(CONFIG_SENSORS_SGP30),y)
CSRCS += sgp30.c
endif
diff --git a/drivers/sensors/scd41.c b/drivers/sensors/scd41.c
new file mode 100644
index 0000000000..1009a765a2
--- /dev/null
+++ b/drivers/sensors/scd41.c
@@ -0,0 +1,1030 @@
+/****************************************************************************
+ * 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/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
+ sem_t devsem;
+ 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 /* 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(¶m, priv->altitude_comp);
+ scd41_write_cmd(priv, SCD41_CMD_SET_ALT_COMPENSATION, ¶m, 1);
+
+ /* Set temperature offset. */
+
+ scd41_set_command_param(¶m, priv->temperature_offset);
+ scd41_write_cmd(priv, SCD41_CMD_SET_TEMP_OFFSET, ¶m, 1);
+
+ /* Set pressure compensation. */
+
+ scd41_set_command_param(¶m, priv->pressure_comp);
+ scd41_write_cmd(priv, SCD41_CMD_SET_PRESSURE_COMP, ¶m, 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 = nxsem_wait_uninterruptible(&priv->devsem);
+ 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--;
+ }
+
+ nxsem_post(&priv->devsem);
+ 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 = nxsem_wait_uninterruptible(&priv->devsem);
+ 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)
+ {
+ nxsem_destroy(&priv->devsem);
+ kmm_free(priv);
+ return OK;
+ }
+
+ nxsem_post(&priv->devsem);
+ 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 = nxsem_wait_uninterruptible(&priv->devsem);
+ 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.
+ */
+
+ nxsem_post(&priv->devsem);
+ 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;
+ }
+ }
+
+ nxsem_post(&priv->devsem);
+ 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 = nxsem_wait_uninterruptible(&priv->devsem);
+ 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.
+ */
+
+ nxsem_post(&priv->devsem);
+ 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(¶m, priv->temperature_offset);
+ ret = scd41_write_cmd(priv, SCD41_CMD_SET_TEMP_OFFSET, ¶m, 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(¶m, priv->pressure_comp);
+ ret = scd41_write_cmd(priv, SCD41_CMD_SET_PRESSURE_COMP,
+ ¶m, 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(¶m, priv->altitude_comp);
+ ret = scd41_write_cmd(priv, SCD41_CMD_SET_ALT_COMPENSATION,
+ ¶m, 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(¶m, arg);
+ ret = scd41_write_cmd(priv, SCD41_CMD_SET_FRC, ¶m, 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(¶m, arg);
+ ret = scd41_write_cmd(priv, SCD41_CMD_SET_ASC, ¶m, 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;
+ }
+
+ nxsem_post(&priv->devsem);
+ 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 != NULL && inode->i_private != NULL);
+ priv = (FAR struct scd41_dev_s *)inode->i_private;
+
+ /* Get exclusive access */
+
+ ret = nxsem_wait_uninterruptible(&priv->devsem);
+ if (ret < 0)
+ {
+ return ret;
+ }
+
+ /* 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 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 = (FAR struct scd41_dev_s *)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;
+
+ nxsem_init(&priv->devsem, 0, 1);
+
+ /* 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);
+ kmm_free(priv);
+ }
+
+ return ret;
+}
+#endif /* CONFIG_SCD41_I2C */
+
+#endif /* CONFIG_SENSORS_SCD41 */
diff --git a/include/nuttx/sensors/scd41.h b/include/nuttx/sensors/scd41.h
new file mode 100644
index 0000000000..f3831363f6
--- /dev/null
+++ b/include/nuttx/sensors/scd41.h
@@ -0,0 +1,75 @@
+/****************************************************************************
+ * include/nuttx/sensors/scd41.h
+ *
+ * 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.
+ *
+ ****************************************************************************/
+
+#ifndef __INCLUDE_NUTTX_SENSORS_SCD41_H
+#define __INCLUDE_NUTTX_SENSORS_SCD41_H
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/sensors/ioctl.h>
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+#define CONFIG_SCD41_ADDR 0x62
+
+/****************************************************************************
+ * Public Types
+ ****************************************************************************/
+
+struct i2c_master_s; /* Forward reference */
+
+struct scd41_conv_data_s
+{
+ float temperature; /* Celsius */
+ float humidity; /* RH-% */
+ float co2; /* CO₂ PPM */
+};
+
+/****************************************************************************
+ * Public Function Prototypes
+ ****************************************************************************/
+
+#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);
+
+#endif
+
+#endif /* __INCLUDE_NUTTX_SENSORS_SCD41_H */
