sht25.c

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/*
 * Copyright (c) 2015, Zolertia <http://www.zolertia.com>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. 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.
 * 3. Neither the name of the Institute 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 INSTITUTE 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
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * This file is part of the Contiki operating system.
 *
 */
/**
 * \file
 *         SHT25 temperature and humidity sensor driver
 * \author
 *         Antonio Lignan <alinan@zolertia.com>
 */
#include <stdio.h>
#include "contiki.h"
#include "i2cmaster.h"
#include "dev/sht25.h"
#include "lib/sensors.h"
/*---------------------------------------------------------------------------*/
static uint8_t enabled;
/*---------------------------------------------------------------------------*/
static int
configure(int type, int value)
{
  if(type != SENSORS_ACTIVE) {
    return SHT25_ERROR;
  }
  if(value) {
    i2c_enable();
  } else {
    i2c_disable();
  }
  enabled = value;
  return 0;
}
/*---------------------------------------------------------------------------*/
static int
status(int type)
{
  switch(type) {
  case SENSORS_ACTIVE:
  case SENSORS_READY:
    return enabled;
  }
  return 0;
}
/*---------------------------------------------------------------------------*/
static uint16_t
sht25_read_reg(uint8_t reg)
{
  uint8_t buf[] = { 0x00, 0x00 };
  uint16_t retval;
  uint8_t rtx = reg;
 
  /* transmit the register to read */
  i2c_transmitinit(SHT25_ADDR);
  while(i2c_busy());
  i2c_transmit_n(1, &rtx);
  while(i2c_busy());
  /* receive the data */
  i2c_receiveinit(SHT25_ADDR);
  while(i2c_busy());
  i2c_receive_n(2, &buf[0]);
  while(i2c_busy());
 
  retval = (uint16_t)(buf[0] << 8 | (buf[1]));
  return retval;
}
/*---------------------------------------------------------------------------*/
static int16_t
sht25_convert(uint8_t variable, uint16_t value)
{
  int16_t rd;
  uint32_t buff;
  buff = (uint32_t)value;
  if(variable == SHT25_VAL_TEMP) {
    buff *= 17572;
    buff = buff >> 16;
    rd = (int16_t)buff - 4685;
  } else {
    buff *= 12500;
    buff = buff >> 16;
    rd = (int16_t)buff - 600;
    rd = (rd > 10000) ? 10000 : rd;
  }
  return rd;
}
/*---------------------------------------------------------------------------*/
static int16_t
sht25_read(uint8_t variable)
{
  int16_t rd;
  uint16_t raw;
 
  if((variable != SHT25_VAL_TEMP) && (variable != SHT25_VAL_HUM)) {
    return SHT25_ERROR;
  }
  raw = sht25_read_reg(variable);
  rd = sht25_convert(variable, raw);
  return rd;
}
/*---------------------------------------------------------------------------*/
static int
value(int type)
{
  return sht25_read(type);
}
/*---------------------------------------------------------------------------*/
SENSORS_SENSOR(sht25, SHT25_SENSOR, value, configure, status);
/*---------------------------------------------------------------------------*/