dht_saul.c
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/*
* Copyright (C) 2016 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.
*/
/**
* @ingroup drivers_dht
* @{
*
* @file
* @brief SAUL adaption for DHT devices
*
* The values exported to SAUL for DHT devices are buffered, meaning that new
* values will only be read from the device, if the buffered values are older
* then 1 second (being exactly the maximum sampling time for DHT devices).
*
* This buffering does further introduce a coupling between both SAUL endpoints,
* meaning that if you read from both endpoints after each other, both values
* are from the same sensor reading.
*
* @author Hauke Petersen <hauke.petersen@fu-berlin.de>
*
* @}
*/
#include <string.h>
#include "saul.h"
#include "dht.h"
#include "xtimer.h"
#define DHT_SAUL_HOLD_TIME (1000 * 1000U) /* 1s */
static int16_t temp, hum;
static uint32_t last = 0;
static int check_and_read(void *dev, phydat_t *res, int16_t *val, uint8_t unit)
{
dht_t *d = (dht_t *)dev;
uint32_t now = xtimer_now_usec();
if ((now - last) > DHT_SAUL_HOLD_TIME) {
dht_read(d, &temp, &hum);
last = now;
}
else {
(void)d;
}
res->val[0] = *val;
memset(&res->val[1], 0, 2 * sizeof(int16_t));
res->unit = unit;
res->scale = -1;
return 1;
}
static int read_temp(void *dev, phydat_t *res)
{
return check_and_read(dev, res, &temp, UNIT_TEMP_C);
}
static int read_hum(void *dev, phydat_t *res)
{
return check_and_read(dev, res, &hum, UNIT_PERCENT);
}
const saul_driver_t dht_temp_saul_driver = {
.read = read_temp,
.write = saul_notsup,
.type = SAUL_SENSE_TEMP
};
const saul_driver_t dht_hum_saul_driver = {
.read = read_hum,
.write = saul_notsup,
.type = SAUL_SENSE_HUM
};