mirror of
https://github.com/RIOT-OS/RIOT.git
synced 2024-12-29 04:50:03 +01:00
579a67be03
The DHT11/DHT21/DHT22 cannot be sampled more than once a second. Previously, a global cache was added to the SAUL adaption of the dht driver to answer with stored values for one second after the last read. This however had two disadvantages: - The global cache was shared for all DHTXX devices connected. As a result incorrect values were delivered when reading out multiple sensors over SAUL with less than 1 second delay in between - A user of the low level API will had to implement the same caching strategy, resulting in code duplication By moving the hold logic to the driver, both limitations can be overcome.
123 lines
3.3 KiB
C
123 lines
3.3 KiB
C
/*
|
|
* Copyright 2015 Ludwig Knüpfer,
|
|
* 2015 Christian Mehlis
|
|
* 2016-2017 Freie Universität Berlin
|
|
*
|
|
* 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.
|
|
*/
|
|
|
|
/**
|
|
* @defgroup drivers_dht DHT Family of Humidity and Temperature Sensors
|
|
* @ingroup drivers_sensors
|
|
* @ingroup drivers_saul
|
|
* @brief Device driver for the DHT Family of humidity
|
|
* and temperature sensors
|
|
*
|
|
* This driver provides @ref drivers_saul capabilities.
|
|
*
|
|
* @{
|
|
*
|
|
* @file
|
|
* @brief Device driver interface for the DHT family of humidity
|
|
* and temperature sensors
|
|
*
|
|
* @author Ludwig Knüpfer <ludwig.knuepfer@fu-berlin.de
|
|
* @author Christian Mehlis <mehlis@inf.fu-berlin.de>
|
|
* @author Hauke Petersen <hauke.petersen@fu-berlin.de>
|
|
*/
|
|
|
|
#ifndef DHT_H
|
|
#define DHT_H
|
|
|
|
#include <stdint.h>
|
|
|
|
#include "periph/gpio.h"
|
|
|
|
#ifdef __cplusplus
|
|
extern "C" {
|
|
#endif
|
|
|
|
/**
|
|
* @brief Possible return codes
|
|
*/
|
|
enum {
|
|
DHT_OK = 0, /**< all good */
|
|
DHT_NOCSUM = -1, /**< checksum error */
|
|
DHT_TIMEOUT = -2, /**< communication timed out */
|
|
DHT_NODEV = -3 /**< device type not defined */
|
|
};
|
|
|
|
/**
|
|
* @brief Data type for storing DHT sensor readings
|
|
*/
|
|
typedef struct {
|
|
uint16_t humidity; /**< relative deca-humidity */
|
|
uint16_t temperature; /**< temperature in deca-Celsius */
|
|
} dht_data_t;
|
|
|
|
/**
|
|
* @brief Device type of the DHT device
|
|
*/
|
|
typedef enum {
|
|
DHT11, /**< DHT11 device identifier */
|
|
DHT22, /**< DHT22 device identifier */
|
|
DHT21 = DHT22 /**< DHT21 device identifier */
|
|
} dht_type_t;
|
|
|
|
/**
|
|
* @brief Configuration parameters for DHT devices
|
|
*/
|
|
typedef struct {
|
|
gpio_t pin; /**< GPIO pin of the device's data pin */
|
|
dht_type_t type; /**< type of the DHT device */
|
|
gpio_mode_t in_mode; /**< input pin configuration, with or without pull
|
|
* resistor */
|
|
|
|
} dht_params_t;
|
|
|
|
/**
|
|
* @brief Device descriptor for DHT sensor devices
|
|
*/
|
|
typedef struct {
|
|
dht_params_t params; /**< Device parameters */
|
|
dht_data_t last_val; /**< Values of the last measurement */
|
|
uint32_t last_read_us; /**< Time of the last measurement */
|
|
} dht_t;
|
|
|
|
/**
|
|
* @brief Initialize a new DHT device
|
|
*
|
|
* @param[out] dev device descriptor of a DHT device
|
|
* @param[in] params configuration parameters
|
|
*
|
|
* @return 0 on success
|
|
* @return -1 on error
|
|
*/
|
|
int dht_init(dht_t *dev, const dht_params_t *params);
|
|
|
|
/**
|
|
* @brief get a new temperature and humidity value from the device
|
|
*
|
|
* @note if reading fails or checksum is invalid, no new values will be
|
|
* written into the result values
|
|
*
|
|
* @param[in] dev device descriptor of a DHT device
|
|
* @param[out] temp temperature value [in °C * 10^-1]
|
|
* @param[out] hum relative humidity value [in percent * 10^-1]
|
|
*
|
|
* @retval `DHT_OK` Success
|
|
* @retval `DHT_NOCSUM` Checksum error
|
|
* @retval `DHT_TIMEOUT` Reading data timed out (check wires!)
|
|
* @retval `DHT_NODEV` Unsupported device type specified
|
|
*/
|
|
int dht_read(dht_t *dev, int16_t *temp, int16_t *hum);
|
|
|
|
#ifdef __cplusplus
|
|
}
|
|
#endif
|
|
|
|
#endif /* DHT_H */
|
|
/** @} */
|