drivers/shtc1: Initial support for the SHTC1 temperature and humidity sensor

drivers/Makefile.include

@@ -210,6 +210,10 @@ ifneq (,$(filter sdcard_spi,$(USEMODULE)))
   USEMODULE_INCLUDES += $(RIOTBASE)/drivers/sdcard_spi/include
 endif
 
+ifneq (,$(filter shtc1,$(USEMODULE)))
+  USEMODULE_INCLUDES += $(RIOTBASE)/drivers/shtc1/include
+endif
+
 ifneq (,$(filter si114x,$(USEMODULE)))
   USEMODULE_INCLUDES += $(RIOTBASE)/drivers/si114x/include
 endif

drivers/include/shtc1.h

@@ -0,0 +1,127 @@
+/*
+ * Copyright 2017, RWTH Aachen. All rights reserved.
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @defgroup    drivers_shtc1
+ * @ingroup     drivers_sensors
+ * @name        Device driver interface for the SHTC1 Temperature and humidity sensor
+ * @{
+ *
+ * @file
+ * @brief       Device driver interface for the SHTC1 Temperature and humidity sensor
+ *
+ * @author      Steffen Robertz <[email protected]>
+ * @author      Josua Arndt <[email protected]>
+ */
+
+#ifndef SHTC1_H
+#define SHTC1_H
+
+#include <stdint.h>
+#include "periph/i2c.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef enum {
+    CRC_DISABLED = 0,
+    CRC_ENABLED
+} shtc1_crc_type_t;
+
+/**
+ * @brief   value struct, where all results obtained from the sensor will be saved.
+ * @{
+ */
+typedef struct {
+    float temp;         /**< Temperature after an according call to the measurement function. */
+    float rel_humidity; /**< Relative humidity after an according call to the measuerment funtion. */
+    unsigned int id;    /**< ID read from the sensor, only available after shtc1_id() was called. */
+} shtc1_values_t;
+/** @} */
+
+/**
+ * @brief   settings struct with all relevant parameters
+ * @{
+ */
+typedef struct {
+    i2c_t bus;              /**< I2C bus descriptor. */
+    uint8_t addr;           /**< I2C address of the sensor. */
+    shtc1_crc_type_t crc;   /**< crc check enabled or disabled (CRC_ENABLED/CRC_DISABLED). */
+} shtc1_params_t;
+/** @} */
+
+/**
+ * @brief   device descriptor for the SHTC1
+ * @{
+ */
+typedef struct {
+    shtc1_values_t values;  /**< Values struct, where all read data will be stored. */
+    shtc1_params_t params;  /**< Paramteres struct with all settings set. */
+} shtc1_t;
+/** @} */
+
+enum {
+    SHTC1_OK = 0,
+    SHTC1_ERROR = -1
+};
+
+/**
+ * @brief Initializes the sensor and I2C.
+ *
+ * @param[in] dev       I2C device descriptor.
+ * @param[in] params    SHTC1 parameters to be used.
+ *
+ * @return              SHTC1_OK on a working initialization.
+ * @return              SHTC1_ERROR on error.
+ */
+int8_t shtc1_init(shtc1_t* const dev, const shtc1_params_t* params);
+
+/**
+ * @brief Reads temperature and humidity values.
+ * @details The values will be saved in the device descriptor (values struct).
+ * The temperature is in °C and the humidity in %.
+ *
+ * @param[in] dev       The I2C device descriptor.
+ *
+ * @return              SHTC1_OK if a measurement completed. The values will be stored
+ *                      in the values struct. Temperature in °C and humidity in %.
+ * @return              SHTC1_ERROR on checksum error.
+ */
+int8_t shtc1_measure(shtc1_t* const dev);
+
+/**
+ * @brief Reads the ID and saves it in the device descriptor
+ *
+ * @details             When working correctly ID should equal xxxx'xxxx'xx00'0111 where x is unspecified.
+ *
+ * @param[in] dev       The I2C device descriptor.
+ *
+ * @return              SHTC1_OK on everything done.
+ * @return              SHTC1_ERROR on error.
+ */
+int8_t shtc1_id(shtc1_t* const dev);
+
+/**
+ * @brief Resets sensor
+ *
+ * This will reset all internal state machines and reload calibration data from the memory.
+ *
+ * @param[in] dev       The I2C device descriptor.
+ *
+ * @return              SHTC1_OK on everything done.
+ * @return              SHTC1_ERROR on error.
+ */
+int8_t shtc1_reset(const shtc1_t* const dev);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* SHTC1_H */
+/** @} */

drivers/shtc1/Makefile

@@ -0,0 +1 @@
+include $(RIOTBASE)/Makefile.base

drivers/shtc1/include/shtc1_params.h

@@ -0,0 +1,66 @@
+/*
+ * Copyright 2017, RWTH Aachen. All rights reserved.
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     drivers_shtc1
+ * @name        Default parameters for the SHTC1 Temperature and humidity sensor
+ * @{
+ *
+ * @file
+ * @brief       Default parameters for the SHTC1 Temperature and humidity sensor
+ *
+ * @author      Steffen Robertz <[email protected]>
+ * @author      Josua Arndt <[email protected]>
+ */
+
+#ifndef SHTC1_PARAMS_H
+#define SHTC1_PARAMS_H
+
+#include "board.h"
+#include "shtc1.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief   Default configuration parameters for SHTC1 sensors
+ * @{
+ */
+#ifndef SHTC1_PARAM_I2C
+#define SHTC1_PARAM_I2C        (I2C_DEV(0))
+#endif
+#ifndef SHTC1_PARAM_ADDR
+#define SHTC1_PARAM_ADDR       (0x70)
+#endif
+#ifndef SHTC1_PARAM_CRC
+#define SHTC1_PARAM_CRC        CRC_ENABLED
+#endif
+
+#ifndef SHTC1_PARAMS
+#define SHTC1_PARAMS           { .bus = SHTC1_PARAM_I2C, \
+                                 .addr = SHTC1_PARAM_ADDR, \
+                                 .crc = SHTC1_PARAM_CRC }
+#endif
+/** @} */
+
+/**
+ * @brief   Allocation of SHTC1 configuration
+ */
+static const shtc1_params_t shtc1_params[] = {
+    #ifdef SHTC1_PARAMS_BOARD
+        SHTC1_PARAMS_BOARD
+    #else
+        SHTC1_PARAMS
+    #endif
+};
+#ifdef __cplusplus
+}
+#endif
+#endif /* SHTC1_PARAMS_H */
+/** @} */

drivers/shtc1/include/shtc1_regs.h

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2017, RWTH Aachen. All rights reserved.
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     drivers_shtc1
+ * @name        Register definition for the SHTC1 Temperature and humidity sensor
+ * @{
+ *
+ * @file
+ * @brief       Register definition for the SHTC1 Temperature and humidity sensor
+ *
+ * @author      Steffen Robertz <[email protected]>
+ * @author      Josua Arndt <[email protected]>
+ */
+
+#ifndef SHTC1_REGS_H
+#define SHTC1_REGS_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define SHTC1_CRC                                   (0x31)    /* crc polynomial */
+#define SHTC1_MEASURE_CLOCK_STRETCHING_TEMP_HIGH    (0x7C)
+#define SHTC1_MEASURE_CLOCK_STRETCHING_TEMP_LOW     (0xA2)
+#define SHTC1_COMMAND_RESET_HIGH                    (0x80)
+#define SHTC1_COMMAND_RESET_LOW                     (0x5D)
+#define SHTC1_COMMAND_ID_HIGH                       (0xEF)
+#define SHTC1_COMMAND_ID_LOW                        (0xC8)
+#define SHTC1_ID                                    (0x07)    /* ID Mask */
+
+#ifdef __cplusplus
+}
+#endif
+#endif /* SHTC1_REGS_H */
+/** @} */

drivers/shtc1/shtc1.c

@@ -0,0 +1,136 @@
+/*
+ * Copyright 2017, RWTH-Aachen, Steffen Robertz, Josua Arndt
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     drivers_shtc1
+ * @{
+ *
+ * @file
+ * @brief       Device driver implementation for the Sensirion SHTC1 temperature and humidity sensor
+ *
+ * @author      Steffen Robertz <[email protected]>
+ * @author      Josua Arndt <[email protected]>
+ * @}
+ */
+
+#include "shtc1.h"
+#include "shtc1_regs.h"
+#define ENABLE_DEBUG    (0)
+#include "debug.h"
+#include "assert.h"
+
+
+/*
+ * does a crc check and returns 0 for passed and -1 for failed
+ * 2 bytes will be checked for the checksum, rec_value is pointer
+ * to first value
+ */
+static int8_t _check_crc(uint8_t *rec_values, uint8_t right_crc)
+{
+    uint8_t crc = 0xFF;
+    uint8_t current_byte;
+    uint8_t bit;
+
+    for (current_byte = 0; current_byte < 2; current_byte++) {
+        crc ^= (rec_values[current_byte]);
+        for (bit = 8; bit > 0; bit--) {
+            if (crc & 0x80) {
+                crc = (crc << 1) ^ SHTC1_CRC;
+            }
+            else {
+                crc = (crc << 1);
+            }
+        }
+    }
+    return !(crc == right_crc);
+}
+
+int8_t shtc1_init(shtc1_t *const dev, const shtc1_params_t *params)
+{
+    /* check for a valid device descriptor and parameters */
+    assert(dev && params);
+    /* copy settings into the device descriptor */
+    dev->params = *params;
+    /* Verify the connection by reading the SHTC1's ID and checking its value */
+    if (shtc1_id(dev) != SHTC1_OK || ((dev->values.id & 0x3F) !=  SHTC1_ID)) {
+        return SHTC1_ERROR;
+    }
+    return SHTC1_OK;
+}
+
+int8_t shtc1_measure(shtc1_t *const dev)
+{
+    /* Build and issue the measurement command */
+    uint8_t cmd[] = { SHTC1_MEASURE_CLOCK_STRETCHING_TEMP_HIGH, SHTC1_MEASURE_CLOCK_STRETCHING_TEMP_LOW };
+
+    i2c_acquire(dev->params.bus);
+    if (i2c_write_bytes(dev->params.bus, dev->params.addr, cmd, 2, 0)) {
+        return SHTC1_ERROR;
+    }
+    /* Receive the measurement */
+    /* 16 bit Temperature 
+     * 8 bit  CRC temp
+     * 16 Bit Absolute Humidity
+     * 8 bit CRC Hum
+    */
+    uint8_t received[6];
+    if(i2c_read_bytes(dev->params.bus, dev->params.addr, received, 6, 0)) {
+        return SHTC1_ERROR;
+    }
+    i2c_release(dev->params.bus);
+    /* get 16bit values and check crc */
+    uint16_t temp_f = ((received[0] << 8) | received[1]);
+    uint16_t abs_humidity = ((received[3] << 8) | received[4]);
+    if (dev->params.crc) {
+        if (!((_check_crc(&received[0], received[2]) == 0) && (_check_crc(&received[3], received[5]) == 0))) {
+            /* crc check failed */
+            DEBUG("CRC Error");
+            return SHTC1_ERROR;
+        }
+        DEBUG("CRC Passed! \n");
+    }
+    /* calculate the relative humidity and convert the temperature to °C */
+    dev->values.temp = (175.0 * temp_f / 65536) - 45;
+    dev->values.rel_humidity = 100 * (abs_humidity / 65536.0);
+
+    return SHTC1_OK;
+}
+
+int8_t shtc1_id(shtc1_t *const dev)
+{
+    /* Build and send measurement command */
+    uint8_t data[] = { SHTC1_COMMAND_ID_HIGH, SHTC1_COMMAND_ID_LOW };
+    int8_t check = 0;
+
+    i2c_acquire(dev->params.bus);
+    check = i2c_write_bytes(dev->params.bus, dev->params.addr, data, 2, 0);
+    /* receive ID and check if the send and receive commands were successfull */
+    check += i2c_read_bytes(dev->params.bus, dev->params.addr, data, 2, 0);
+    i2c_release(dev->params.bus);
+    if (check != 0) {
+        /* error occured */
+        return SHTC1_ERROR;
+    }
+    /* Save ID in device descriptor */
+    dev->values.id = (data[0] << 8) | data[1];
+    return SHTC1_OK;
+}
+
+int8_t shtc1_reset(const shtc1_t *const dev)
+{
+    /* Build and issue the reset command */
+    uint8_t data[] = { SHTC1_COMMAND_RESET_HIGH, SHTC1_COMMAND_RESET_LOW };
+
+    i2c_acquire(dev->params.bus);
+    if (i2c_write_bytes(dev->params.bus, dev->params.addr, data, 2, 0)) {
+        i2c_release(dev->params.bus);
+        return SHTC1_ERROR;
+    }
+    i2c_release(dev->params.bus);
+    return SHTC1_OK;
+}

tests/driver_shtc1/Makefile

@@ -0,0 +1,9 @@
+APPLICATION = driver_shtc1
+include ../Makefile.tests_common
+
+FEATURES_REQUIRED = periph_i2c
+
+USEMODULE += shtc1
+USEMODULE += xtimer
+
+include $(RIOTBASE)/Makefile.include