93 lines
2.2 KiB
C
93 lines
2.2 KiB
C
/**
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* Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
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*
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* SPDX-License-Identifier: BSD-3-Clause
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**/
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#include <stdio.h>
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#include <math.h>
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#include "pico/stdlib.h"
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#include "hardware/gpio.h"
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#ifdef PICO_DEFAULT_LED_PIN
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#define LED_PIN PICO_DEFAULT_LED_PIN
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#endif
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const uint DHT_PIN = 15;
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const uint MAX_TIMINGS = 85;
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typedef struct {
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float humidity;
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float temp_celsius;
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} dht_reading;
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void read_from_dht(dht_reading *result);
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int main() {
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stdio_init_all();
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gpio_init(DHT_PIN);
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#ifdef LED_PIN
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gpio_init(LED_PIN);
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gpio_set_dir(LED_PIN, GPIO_OUT);
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#endif
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while (1) {
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dht_reading reading;
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read_from_dht(&reading);
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float fahrenheit = (reading.temp_celsius * 9 / 5) + 32;
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printf("Humidity = %.1f%%, Temperature = %.1fC (%.1fF)\n",
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reading.humidity, reading.temp_celsius, fahrenheit);
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sleep_ms(2000);
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}
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}
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void read_from_dht(dht_reading *result) {
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int data[5] = {0, 0, 0, 0, 0};
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uint last = 1;
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uint j = 0;
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gpio_set_dir(DHT_PIN, GPIO_OUT);
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gpio_put(DHT_PIN, 0);
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sleep_ms(20);
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gpio_set_dir(DHT_PIN, GPIO_IN);
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#ifdef LED_PIN
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gpio_put(LED_PIN, 1);
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#endif
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for (uint i = 0; i < MAX_TIMINGS; i++) {
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uint count = 0;
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while (gpio_get(DHT_PIN) == last) {
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count++;
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sleep_us(1);
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if (count == 255) break;
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}
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last = gpio_get(DHT_PIN);
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if (count == 255) break;
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if ((i >= 4) && (i % 2 == 0)) {
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data[j / 8] <<= 1;
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if (count > 16) data[j / 8] |= 1;
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j++;
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}
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}
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#ifdef LED_PIN
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gpio_put(LED_PIN, 0);
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#endif
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if ((j >= 40) && (data[4] == ((data[0] + data[1] + data[2] + data[3]) & 0xFF))) {
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result->humidity = (float) ((data[0] << 8) + data[1]) / 10;
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if (result->humidity > 100) {
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result->humidity = data[0];
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}
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result->temp_celsius = (float) (((data[2] & 0x7F) << 8) + data[3]) / 10;
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if (result->temp_celsius > 125) {
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result->temp_celsius = data[2];
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}
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if (data[2] & 0x80) {
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result->temp_celsius = -result->temp_celsius;
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}
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} else {
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printf("Bad data\n");
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}
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}
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