htu21d: sensor added

Signed-off-by: William Penner <william.penner@intel.com>
Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>

src/htu21d/htu21d.h

@@ -0,0 +1,169 @@
+/*
+ * Author: William Penner <william.penner@intel.com>
+ * Copyright (c) 2014 Intel Corporation.
+ *
+ * Based on code adapted from the kernel HTU21 driver and
+ * code by: Yevgeniy Kiveisha <yevgeniy.kiveisha@intel.com>
+ * Copyright (c) 2014 Intel Corporation.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#pragma once
+
+#include <string>
+#include <mraa/i2c.h>
+#include <math.h>
+
+#define HTU21D_NAME     "htu21d"
+#define HTU21D_I2C_ADDRESS  0x40
+
+/* HTU21 Commands */
+#define HTU21D_T_MEASUREMENT_HM   0xE3
+#define HTU21D_RH_MEASUREMENT_HM  0xE5
+
+namespace upm {
+
+/**
+ * @brief HTU21D humidity sensor library
+ * @defgroup htu21d libupm-htu21
+ */
+
+/**
+ * @brief C++ API for HTU21D chip (Atmospheric Pressure Sensor)
+ *
+ * Measurement Specialties [HTU21D]
+ * (http://www.meas-spec.com/downloads/HTU21D.pdf)
+ * is a digital humidity sensor with temperature output.
+ * RH will report between 0 and 100% and temperature range is
+ * -40 to +125 degC
+ *
+ * @ingroup htu21d i2c
+ * @snippet htu21d.cxx Interesting
+ * @image html htu21d.jpeg
+ */
+class HTU21D {
+    public:
+        /**
+         * Instanciates a HTU21D object
+         *
+         * @param bus number of used bus
+         * @param devAddr address of used i2c device
+         * @param mode HTU21D oversampling
+         */
+        HTU21D (int bus=0, int devAddr=HTU21D_I2C_ADDRESS);
+
+        /**
+         * HTU21D object destructor, basicaly it close i2c connection.
+         */
+        ~HTU21D ();
+
+        /**
+         * Initiate a temp/pressure mesasurement and wait for function
+         * to complete.  The humidity and temp registers can be read
+         * after this call.
+         */
+        int sampleData(void);
+        
+        /**
+         * Get the current measured humidity [RH * 1000]
+         * To convert to Relative Humidity, divide by 1000
+         *
+         */
+        int32_t getHumidity(void);
+
+        /**
+         * Get the humidity cell temperature [degC * 1000]
+         * To convert to Temperature, divide by 1000
+         */
+        int32_t getTemperature(void);
+        
+        /**
+         * Reads both temperature and humidity together
+         * To convert to Relative Humidity, divide by 1000
+         * To convert to Temperature, divide by 1000
+         *
+         * @param pointer to int32_t buffer for temp
+         */
+        int32_t getRHumidity(int32_t* iTemperature);
+        
+        /**
+         * Using the current humidity and temperature the function
+         * will calculate the compensated RH using the equation from
+         * the datasheet.
+         */
+        int32_t getCompRH(void);
+        
+        /**
+         * Function intended to test the device and verify it
+         * is correctly operating.
+         *
+         */
+        int testSensor(void);
+        
+        /**
+         * Read 1 to 4 bytes from i2c registers
+         *
+         * @param reg address of a register
+         * @param puint32 pointer to buffer for register data
+         * @param ibytes number of bytes to be returned
+         */
+        mraa_result_t i2cReadRegValue (int reg, uint32_t* puint32, int ibytes);
+
+        /**
+         * Read two bytes register
+         *
+         * @param reg address of a register
+         */
+        uint16_t i2cReadReg_16 (int reg);
+
+        /**
+         * Write to one byte register
+         *
+         * @param reg address of a register
+         * @param value byte to be written
+         */
+        mraa_result_t i2cWriteReg (uint8_t reg, uint8_t value);
+
+        /**
+         * Read one byte register
+         *
+         * @param reg address of a register
+         */
+        uint8_t i2cReadReg_8 (int reg);
+
+    private:
+
+        /**
+         * Convert temp register to value * 1000
+         */
+        int32_t htu21_temp_ticks_to_millicelsius(int ticks);
+
+        /**
+         * Convert temp register to value * 1000
+         */
+        int32_t htu21_rh_ticks_to_per_cent_mille(int ticks);
+
+        std::string m_name;
+
+        int m_controlAddr;
+        int m_bus;
+        mraa_i2c_context m_i2ControlCtx;
+        
+        int32_t m_temperature;
+        int32_t m_humidity;
+};
+
+}