hih6130.c
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/*
* Copyright (C) 2015 Eistec AB
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
/**
* @ingroup drivers_hih6130
* @{
*
* @file
* @brief Device driver implementation for Honeywell HumidIcon Digital
* Humidity/Temperature Sensors: HIH-6130/6131 Series
*
* @author Joakim Nohlgård <joakim.nohlgard@eistec.se>
*
* @}
*/
#include <stddef.h>
#include <stdint.h>
#include "hih6130.h"
#include "periph/i2c.h"
#include "xtimer.h"
#define ENABLE_DEBUG (0)
#include "debug.h"
/* Humidity is stored in the first 2 bytes of data */
#define HIH6130_HUMIDITY_DATA_LENGTH (2)
/* Humidity + temperature data is 4 bytes long */
#define HIH6130_FULL_DATA_LENGTH (4)
/* Bit mask for the status bits in the first byte transferred */
#define HIH6130_STATUS_MASK (0xc0)
/* Bit mask for the humidity data */
#define HIH6130_HUMIDITY_MASK (0x3fff)
/* Temperature data is left adjusted within the word */
#define HIH6130_TEMPERATURE_SHIFT (2)
enum {
HIH6130_STATUS_OK = 0x00,
/**
* stale data: data that has already been fetched since the last measurement
* cycle, or data fetched before the first measurement has been completed.
*/
HIH6130_STATUS_STALE_DATA = 0x40,
HIH6130_STATUS_COMMAND_MODE = 0x80,
HIH6130_STATUS_DIAGNOSTIC = 0xc0,
};
/** @brief Delay between requesting a measurement and data becoming ready */
#define MEASUREMENT_DELAY (50LU * US_PER_MS)
/** @brief Trigger a new measurement on the sensor */
static inline int hih6130_measurement_request(const hih6130_t *dev)
{
i2c_acquire(dev->i2c);
/* An empty write request triggers a new measurement */
if (i2c_write_bytes(dev->i2c, dev->addr, NULL, 0) < 0) {
i2c_release(dev->i2c);
return -1;
}
i2c_release(dev->i2c);
return 0;
}
void hih6130_init(hih6130_t *dev, i2c_t i2c, uint8_t address)
{
/* write device descriptor */
dev->i2c = i2c;
dev->addr = address;
}
static inline int hih6130_get_humidity_temperature_raw(const hih6130_t *dev, uint16_t *humidity_raw, uint16_t *temperature_raw)
{
int status;
uint8_t buf[HIH6130_FULL_DATA_LENGTH];
i2c_acquire(dev->i2c);
if (i2c_read_bytes(dev->i2c, dev->addr, &buf[0], sizeof(buf)) != sizeof(buf)) {
i2c_release(dev->i2c);
return -1;
}
i2c_release(dev->i2c);
/* data is in big-endian format, with status bits in the first byte. */
switch (buf[0] & HIH6130_STATUS_MASK) {
case HIH6130_STATUS_OK:
status = 0;
break;
case HIH6130_STATUS_STALE_DATA:
status = 1;
break;
default:
return -2;
}
*humidity_raw = ((buf[0] << 8) | buf[1]) & HIH6130_HUMIDITY_MASK;
*temperature_raw = (((buf[2] << 8) | buf[3]) >> HIH6130_TEMPERATURE_SHIFT);
return status;
}
int hih6130_get_humidity_temperature_float(const hih6130_t *dev,
float *relative_humidity_percent, float *temperature_celsius)
{
uint16_t hum_raw, temp_raw;
int status;
if (hih6130_measurement_request(dev) != 0) {
return -1;
}
xtimer_usleep(MEASUREMENT_DELAY);
status = hih6130_get_humidity_temperature_raw(dev, &hum_raw, &temp_raw);
if (status < 0) {
return -1;
}
if (relative_humidity_percent != NULL) {
*relative_humidity_percent = hum_raw * (100.f / 16383.f);
}
if (temperature_celsius != NULL) {
*temperature_celsius = temp_raw * (165.f / 16383.f) - 40.f;
}
return status;
}