sht21.h

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/* Copyright 2013-2014, Peter A. Bigot
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * * Redistributions of source code must retain the above copyright notice,
 *   this list of conditions and the following disclaimer.
 *
 * * 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.
 *
 * * Neither the name of the software 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
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 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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 */

#ifndef BSP430_SENSORS_SHT21_H
#define BSP430_SENSORS_SHT21_H

#include <bsp430/serial.h>
#include <bsp430/periph/timer.h>

#define BSP430_SENSORS_SHT21_I2C_ADDRESS 0x40

#define BSP430_SENSORS_SHT21_RESET_DELAY_MS 15

#define BSP430_SENSORS_SHT21_CONFIG_H12T14 0x00

#define BSP430_SENSORS_SHT21_CONFIG_H8T12 0x01

#define BSP430_SENSORS_SHT21_CONFIG_H10T13 0x80

#define BSP430_SENSORS_SHT21_CONFIG_H11T11 0x81

#define BSP430_SENSORS_SHT21_CONFIG_RESOLUTION_MASK 0x81

#define BSP430_SENSORS_SHT21_CONFIG_EOB_MASK 0x40

#define BSP430_SENSORS_SHT21_CONFIG_HEATER_MASK 0x04

#define BSP430_SENSORS_SHT21_EIC_LENGTH 8

#define BSP430_SENSORS_SHT21_EIC_IS_SHT21(eic_) ((0x00 == (eic_)[0]) && (0x80 == (eic_)[1]))

#define BSP430_SENSORS_SHT21_EIC_IS_HTU21D(eic_) ((0x48 == (eic_)[0]) && (0x54 == (eic_)[1]))

/* RH_pph = -6 + 125 * S / 2^16 */
#define BSP430_SENSORS_SHT21_HUMIDITY_RAW_TO_ppth(raw_) (unsigned int)(((1250UL * (raw_)) >> 16) - 60)

/* T_dC = -46.85 + 175.72 * S / 2^16
 * T_cK = 27315 - 4685 + 17572 * S / 2^16
 *      = 22630 + 17572 * S / 2^16
 */
#define BSP430_SENSORS_SHT21_TEMPERATURE_RAW_TO_cK(raw_) (22630U + (unsigned int)((17572UL * (raw_)) >> 16))

#define BSP430_SENSORS_SHT21_TEMPERATURE_RAW_TO_dK(raw_) ((unsigned int)((5 + BSP430_SENSORS_SHT21_TEMPERATURE_RAW_TO_cK(raw_)) / 10))

#ifndef BSP430_SENSORS_SHT21_IS_HTU21D

#define BSP430_SENSORS_SHT21_IS_HTU21D 1
#endif /* BSP430_SENSORS_SHT21_IS_HTU21D */

typedef struct sBSP430sensorsSHT21sample {
  unsigned int temperature_raw;

  unsigned int humidity_raw;

  int temperature_dK;

  int humidity_ppth;
} sBSP430sensorsSHT21sample;

typedef sBSP430sensorsSHT21sample * hBSP430sensorsSHT21sample;

int iBSP430sensorsSHT21crc (const uint8_t * data,
                            int len);

int iBSP430sensorsSHT21eic (hBSP430halSERIAL i2c,
                            uint8_t * eic);

int iBSP430sensorsSHT21configuration (hBSP430halSERIAL i2c,
                                      int resolution,
                                      int heater);

int iBSP430sensorsSHT21reset (hBSP430halSERIAL i2c);

typedef enum eBSP430sensorsSHT21measurement {
  eBSP430sensorsSHT21measurement_HUMIDITY, 
  eBSP430sensorsSHT21measurement_TEMPERATURE 
} eBSP430sensorsSHT21measurement;

int iBSP430sensorsSHT21initiateMeasurement (hBSP430halSERIAL i2c,
                                            int hold_master,
                                            eBSP430sensorsSHT21measurement type);

int iBSP430sensorsSHT21getMeasurement (hBSP430halSERIAL i2c,
                                       int hold_master,
                                       uint16_t * rawp);

int iBSP430sensorsSHT21getSample (hBSP430halSERIAL i2c,
                                  hBSP430sensorsSHT21sample sample);

#endif /* BSP430_SENSORS_SHT21_H */