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/*
* Copyright 2015 Ludwig Knüpfer
* 2015 Christian Mehlis
* 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 Device driver implementation for the DHT 11 and 22
* temperature and humidity sensor
*
* @author Ludwig Knüpfer <ludwig.knuepfer@fu-berlin.de>
* @author Christian Mehlis <mehlis@inf.fu-berlin.de>
* @author Hauke Petersen <hauke.petersen@fu-berlin.de>
*
* @}
*/
#include <stdint.h>
#include <string.h>
#include "log.h"
#include "xtimer.h"
#include "timex.h"
#include "periph/gpio.h"
#include "dht.h"
#include "dht_params.h"
#define ENABLE_DEBUG (0)
#include "debug.h"
#define PULSE_WIDTH_THRESHOLD (40U)
/**
* @brief Allocation of memory for device descriptors
*/
dht_t dht_devs[DHT_NUMOF];
static uint16_t read(gpio_t pin, int bits)
{
uint16_t res = 0;
for (int i = 0; i < bits; i++) {
uint32_t start, end;
res <<= 1;
/* measure the length between the next rising and falling flanks (the
* time the pin is high - smoke up :-) */
while (!gpio_read(pin));
start = xtimer_now_usec();
while (gpio_read(pin));
end = xtimer_now_usec();
/* if the high phase was more than 40us, we got a 1 */
if ((end - start) > PULSE_WIDTH_THRESHOLD) {
res |= 0x0001;
}
}
return res;
}
void dht_auto_init(void)
{
for (unsigned i = 0; i < DHT_NUMOF; i++) {
if (dht_init(&dht_devs[i], &dht_params[i]) < 0) {
LOG_ERROR("Unable to initialize DHT sensor #%i\n", i);
}
#ifdef MODULE_SAUL_REG
for (int j = 0; j < 2; j++) {
dht_saul_reg[i][j].dev = &dht_devs[i];
saul_reg_add(&dht_saul_reg[i][j]);
}
#endif
}
}
int dht_init(dht_t *dev, const dht_params_t *params)
{
DEBUG("dht_init\n");
memcpy(dev, params, sizeof(dht_t));
if (gpio_init(dev->pin, GPIO_OUT) == -1) {
return -1;
}
gpio_set(dev->pin);
xtimer_usleep(2000 * US_PER_MS);
DEBUG("dht_init: success\n");
return 0;
}
int dht_read(dht_t *dev, int16_t *temp, int16_t *hum)
{
uint8_t csum, sum;
uint16_t raw_hum, raw_temp;
/* send init signal to device */
gpio_clear(dev->pin);
xtimer_usleep(20 * US_PER_MS);
gpio_set(dev->pin);
xtimer_usleep(40);
/* sync on device */
gpio_init(dev->pin, dev->in_mode);
while (!gpio_read(dev->pin)) ;
while (gpio_read(dev->pin)) ;
/*
* data is read in sequentially, highest bit first:
* 40 .. 24 23 .. 8 7 .. 0
* [humidity][temperature][checksum]
*/
/* read the humidity, temperature, and checksum bits */
raw_hum = read(dev->pin, 16);
raw_temp = read(dev->pin, 16);
csum = (uint8_t)read(dev->pin, 8);
/* set pin high again - so we can trigger the next reading by pulling it low
* again */
gpio_init(dev->pin, GPIO_OUT);
gpio_set(dev->pin);
/* validate the checksum */
sum = (raw_temp >> 8) + (raw_temp & 0xff) + (raw_hum >> 8) + (raw_hum & 0xff);
if ((sum != csum) || (csum == 0)) {
DEBUG("error: checksum invalid\n");
return -1;
}
/* parse the RAW values */
DEBUG("RAW values: temp: %7i hum: %7i\n", (int)raw_temp, (int)raw_hum);
switch (dev->type) {
case DHT11:
*temp = (int16_t)((raw_temp >> 8) * 10);
*hum = (int16_t)((raw_hum >> 8) * 10);
break;
case DHT22:
*hum = (int16_t)raw_hum;
/* if the high-bit is set, the value is negative */
if (raw_temp & 0x8000) {
*temp = (int16_t)((raw_temp & ~0x8000) * -1);
}
else {
*temp = (int16_t)raw_temp;
}
break;
default:
return -2;
}
return 0;
}