209 lines
6.8 KiB
C
209 lines
6.8 KiB
C
/*
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* Copyright (c) 2014, OpenMote Technologies, S.L.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the Institute nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* This file is part of the Contiki operating system.
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*
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*/
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/**
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* \addtogroup platform
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* @{
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*
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* \defgroup openmote
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*
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* \file
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* Driver for the SHT21 temperature and humidity sensor in OpenMote-CC2538.
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*
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* \author
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* Pere Tuset <peretuset@openmote.com>
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*/
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/*---------------------------------------------------------------------------*/
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#include "i2c.h"
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#include "sht21.h"
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/*---------------------------------------------------------------------------*/
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#define SHT21_ADDRESS (0x40)
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#define SHT21_USER_REG_READ (0xE7)
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#define SHT21_USER_REG_WRITE (0xE6)
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#define SHT21_USER_REG_RESERVED_BITS (0x38)
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#define SHT21_RESOLUTION_12b_14b ((0 << 7) | (0 << 0))
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#define SHT21_RESOLUTION_8b_12b ((0 << 7) | (1 << 0))
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#define SHT21_RESOLUTION_10b_13b ((1 << 7) | (0 << 0))
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#define SHT21_RESOLUTION_11b_11b ((1 << 7) | (1 << 0))
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#define SHT21_BATTERY_ABOVE_2V25 (0 << 6)
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#define SHT21_BATTERY_BELOW_2V25 (1 << 6)
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#define SHT21_ONCHIP_HEATER_ENABLE (1 << 2)
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#define SHT21_ONCHIP_HEATER_DISABLE (0 << 2)
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#define SHT21_OTP_RELOAD_ENABLE (0 << 1)
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#define SHT21_OTP_RELOAD_DISABLE (1 << 1)
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#define SHT21_TEMPERATURE_HM_CMD (0xE3)
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#define SHT21_HUMIDITY_HM_CMD (0xE5)
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#define SHT21_TEMPERATURE_NHM_CMD (0xF3)
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#define SHT21_HUMIDITY_NHM_CMD (0xF5)
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#define SHT21_RESET_CMD (0xFE)
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#define SHT21_STATUS_MASK ( 0xFC )
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#define SHT21_DEFAULT_CONFIG (SHT21_RESOLUTION_12b_14b | \
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SHT21_ONCHIP_HEATER_DISABLE | \
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SHT21_BATTERY_ABOVE_2V25 | \
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SHT21_OTP_RELOAD_DISABLE)
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#define SHT21_USER_CONFIG (SHT21_RESOLUTION_8b_12b | \
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SHT21_ONCHIP_HEATER_DISABLE | \
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SHT21_BATTERY_ABOVE_2V25 | \
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SHT21_OTP_RELOAD_DISABLE)
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/*---------------------------------------------------------------------------*/
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/**
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*
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*/
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void
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sht21_init(void)
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{
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uint8_t config[2];
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i2c_init(I2C_SDA_PORT, I2C_SDA_PIN, I2C_SCL_PORT, I2C_SCL_PIN,
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I2C_SCL_NORMAL_BUS_SPEED);
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/* Setup the configuration vector, the first position holds address */
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/* and the second position holds the actual configuration */
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config[0] = SHT21_USER_REG_WRITE;
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config[1] = 0;
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/* Read the current configuration according to the datasheet (pag. 9, fig. 18) */
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i2c_single_send(SHT21_ADDRESS, SHT21_USER_REG_READ);
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i2c_single_receive(SHT21_ADDRESS, &config[1]);
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/* Clean all the configuration bits except those reserved */
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config[1] &= SHT21_USER_REG_RESERVED_BITS;
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/* Set the configuration bits without changing those reserved */
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config[1] |= SHT21_USER_CONFIG;
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i2c_burst_send(SHT21_ADDRESS, config, sizeof(config));
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}
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/*---------------------------------------------------------------------------*/
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/**
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*
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*/
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void
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sht21_reset(void)
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{
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/* Send a soft-reset command according to the datasheet (pag. 9, fig. 17) */
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i2c_single_send(SHT21_ADDRESS, SHT21_RESET_CMD);
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}
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/*---------------------------------------------------------------------------*/
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/**
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*
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*/
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uint8_t
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sht21_is_present(void)
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{
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uint8_t is_present;
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/* Read the current configuration according to the datasheet (pag. 9, fig. 18) */
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i2c_single_send(SHT21_ADDRESS, SHT21_USER_REG_READ);
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i2c_single_receive(SHT21_ADDRESS, &is_present);
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/* Clear the reserved bits according to the datasheet (pag. 9, tab. 8) */
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is_present &= ~SHT21_USER_REG_RESERVED_BITS;
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is_present = ((is_present == SHT21_USER_CONFIG) || (is_present == SHT21_DEFAULT_CONFIG));
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return is_present;
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}
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/*---------------------------------------------------------------------------*/
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/**
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*
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*/
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uint16_t
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sht21_read_temperature(void)
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{
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uint8_t sht21_temperature[2];
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uint16_t temperature;
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/* Read the current temperature according to the datasheet (pag. 8, fig. 15) */
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i2c_single_send(SHT21_ADDRESS, SHT21_TEMPERATURE_HM_CMD);
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i2c_burst_receive(SHT21_ADDRESS, sht21_temperature, sizeof(sht21_temperature));
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temperature = (sht21_temperature[0] << 8) | (sht21_temperature[1] & SHT21_STATUS_MASK);
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return temperature;
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}
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/*---------------------------------------------------------------------------*/
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/**
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*
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*/
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float
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sht21_convert_temperature(uint16_t temperature)
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{
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float result;
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result = -46.85;
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result += 175.72 * (float) temperature / 65536.0;
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return result;
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}
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/*---------------------------------------------------------------------------*/
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/**
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*
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*/
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uint16_t
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sht21_read_humidity(void)
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{
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uint8_t sht21_humidity[2];
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uint16_t humidity;
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/* Read the current humidity according to the datasheet (pag. 8, fig. 15) */
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i2c_single_send(SHT21_ADDRESS, SHT21_HUMIDITY_HM_CMD);
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i2c_burst_receive(SHT21_ADDRESS, sht21_humidity, sizeof(sht21_humidity));
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humidity = (sht21_humidity[0] << 8) | (sht21_humidity[1] & SHT21_STATUS_MASK);
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return humidity;
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}
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/*---------------------------------------------------------------------------*/
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/**
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*
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*/
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float
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sht21_convert_humidity(uint16_t humidity)
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{
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float result;
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result = -6.0;
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result += 125.0 * (float) humidity / 65536.0;
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return result;
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}
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/*---------------------------------------------------------------------------*/
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/** @} */
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