contiki/platform/openmote-cc2538/dev/sht21.c

198 lines
7.0 KiB
C

/*
* Copyright (c) 2014, OpenMote Technologies, S.L.
* 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.
*
*/
/*---------------------------------------------------------------------------*/
/**
* \addtogroup openmote-sht21-sensor
* @{
*
* \file
* Driver for the SHT21 temperature and relative humidity sensor
*
* \author
* Pere Tuset <peretuset@openmote.com>
*/
/*---------------------------------------------------------------------------*/
#include "i2c.h"
#include "sht21.h"
/*---------------------------------------------------------------------------*/
/**
* \name SHT21 address
*/
#define SHT21_ADDRESS (0x40)
/** @} */
/*---------------------------------------------------------------------------*/
/**
* \name SHT21 register addresses and values
* @{
*/
#define SHT21_USER_REG_READ (0xE7)
#define SHT21_USER_REG_WRITE (0xE6)
#define SHT21_USER_REG_RESERVED_BITS (0x38)
#define SHT21_TEMPERATURE_HM_CMD (0xE3)
#define SHT21_HUMIDITY_HM_CMD (0xE5)
#define SHT21_TEMPERATURE_NHM_CMD (0xF3)
#define SHT21_HUMIDITY_NHM_CMD (0xF5)
#define SHT21_RESET_CMD (0xFE)
#define SHT21_STATUS_MASK (0xFC)
#define SHT21_RESOLUTION_12b_14b ((0 << 7) | (0 << 0))
#define SHT21_RESOLUTION_8b_12b ((0 << 7) | (1 << 0))
#define SHT21_RESOLUTION_10b_13b ((1 << 7) | (0 << 0))
#define SHT21_RESOLUTION_11b_11b ((1 << 7) | (1 << 0))
#define SHT21_BATTERY_ABOVE_2V25 (0 << 6)
#define SHT21_BATTERY_BELOW_2V25 (1 << 6)
#define SHT21_ONCHIP_HEATER_ENABLE (1 << 2)
#define SHT21_ONCHIP_HEATER_DISABLE (0 << 2)
#define SHT21_OTP_RELOAD_ENABLE (0 << 1)
#define SHT21_OTP_RELOAD_DISABLE (1 << 1)
/** @} */
/*---------------------------------------------------------------------------*/
/**
* \name SHT21 configuration values
* @{
*/
#define SHT21_DEFAULT_CONFIG (SHT21_RESOLUTION_12b_14b | \
SHT21_ONCHIP_HEATER_DISABLE | \
SHT21_BATTERY_ABOVE_2V25 | \
SHT21_OTP_RELOAD_DISABLE)
#define SHT21_USER_CONFIG (SHT21_RESOLUTION_8b_12b | \
SHT21_ONCHIP_HEATER_DISABLE | \
SHT21_BATTERY_ABOVE_2V25 | \
SHT21_OTP_RELOAD_DISABLE)
/** @} */
/*---------------------------------------------------------------------------*/
void
sht21_init(void)
{
uint8_t config[2];
/* Setup the configuration vector, the first position holds address */
/* and the second position holds the actual configuration */
config[0] = SHT21_USER_REG_WRITE;
config[1] = 0;
/* Read the current configuration according to the datasheet (pag. 9, fig. 18) */
i2c_single_send(SHT21_ADDRESS, SHT21_USER_REG_READ);
i2c_single_receive(SHT21_ADDRESS, &config[1]);
/* Clean all the configuration bits except those reserved */
config[1] &= SHT21_USER_REG_RESERVED_BITS;
/* Set the configuration bits without changing those reserved */
config[1] |= SHT21_USER_CONFIG;
i2c_burst_send(SHT21_ADDRESS, config, sizeof(config));
}
/*---------------------------------------------------------------------------*/
void
sht21_reset(void)
{
/* Send a soft-reset command according to the datasheet (pag. 9, fig. 17) */
i2c_single_send(SHT21_ADDRESS, SHT21_RESET_CMD);
}
/*---------------------------------------------------------------------------*/
uint8_t
sht21_is_present(void)
{
uint8_t status;
uint8_t is_present;
/* Read the current configuration according to the datasheet (pag. 9, fig. 18) */
i2c_single_send(SHT21_ADDRESS, SHT21_USER_REG_READ);
status = i2c_single_receive(SHT21_ADDRESS, &is_present);
if(status != I2C_MASTER_ERR_NONE) {
return 0;
}
/* Clear the reserved bits according to the datasheet (pag. 9, tab. 8) */
is_present &= ~SHT21_USER_REG_RESERVED_BITS;
return (is_present == SHT21_USER_CONFIG) || (is_present == SHT21_DEFAULT_CONFIG);
}
/*---------------------------------------------------------------------------*/
uint16_t
sht21_read_temperature(void)
{
uint8_t sht21_temperature[2];
uint16_t temperature;
/* Read the current temperature according to the datasheet (pag. 8, fig. 15) */
i2c_single_send(SHT21_ADDRESS, SHT21_TEMPERATURE_HM_CMD);
i2c_burst_receive(SHT21_ADDRESS, sht21_temperature, sizeof(sht21_temperature));
temperature = (sht21_temperature[0] << 8) | (sht21_temperature[1] & SHT21_STATUS_MASK);
return temperature;
}
/*---------------------------------------------------------------------------*/
float
sht21_convert_temperature(uint16_t temperature)
{
float result;
result = -46.85;
result += 175.72 * (float)temperature / 65536.0;
return result;
}
/*---------------------------------------------------------------------------*/
uint16_t
sht21_read_humidity(void)
{
uint8_t sht21_humidity[2];
uint16_t humidity;
/* Read the current humidity according to the datasheet (pag. 8, fig. 15) */
i2c_single_send(SHT21_ADDRESS, SHT21_HUMIDITY_HM_CMD);
i2c_burst_receive(SHT21_ADDRESS, sht21_humidity, sizeof(sht21_humidity));
humidity = (sht21_humidity[0] << 8) | (sht21_humidity[1] & SHT21_STATUS_MASK);
return humidity;
}
/*---------------------------------------------------------------------------*/
float
sht21_convert_humidity(uint16_t humidity)
{
float result;
result = -6.0;
result += 125.0 * (float)humidity / 65536.0;
return result;
}
/*---------------------------------------------------------------------------*/
/** @} */