DHT11 readout

main/main.c

@@ -0,0 +1,190 @@
+/*
+ * SPDX-FileCopyrightText: 2010-2022 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: CC0-1.0
+ */
+
+#include <stdio.h>
+#include <inttypes.h>
+#include <time.h>
+#include <string.h>
+#include <sys/time.h>
+
+#include "sdkconfig.h"
+#include "freertos/FreeRTOS.h"
+#include "freertos/task.h"
+#include "esp_chip_info.h"
+#include "esp_flash.h"
+#include "esp_system.h"
+#include "esp_timer.h"
+#include "driver/gpio.h"
+
+// Define the GPIO pin for the DHT11 data line
+#define DHT11_GPIO 0
+
+void read_dht11(uint8_t *humidity_int, uint8_t *humidity_dec,
+                int8_t *temperature_int, uint8_t *temperature_dec,
+                uint8_t *checksum) {
+    uint8_t data[5] = {0};
+
+    // Send start signal: pull the line low for 20ms
+    gpio_set_direction(DHT11_GPIO, GPIO_MODE_OUTPUT);
+    gpio_set_level(DHT11_GPIO, 0);
+    vTaskDelay(pdMS_TO_TICKS(20));
+
+    // Release the line and wait for sensor response
+    gpio_set_level(DHT11_GPIO, 1);
+    gpio_set_direction(DHT11_GPIO, GPIO_MODE_INPUT);
+
+    // Wait for the sensor to pull the line low (~20-40us)
+    while (gpio_get_level(DHT11_GPIO) == 1) {
+        vTaskDelay(pdMS_TO_TICKS(0.1));
+    }
+
+    // Wait for the sensor to pull the line high (~80us)
+    while (gpio_get_level(DHT11_GPIO) == 0) {
+        vTaskDelay(pdMS_TO_TICKS(0.1));
+    }
+
+    // Read 40 bits of data
+    for (int i = 0; i < 40; i++) {
+        // Wait for the start of the bit (low for ~50us)
+        while (gpio_get_level(DHT11_GPIO) == 1) {
+            vTaskDelay(pdMS_TO_TICKS(0.1));
+        }
+        while (gpio_get_level(DHT11_GPIO) == 0) {
+            vTaskDelay(pdMS_TO_TICKS(0.1));
+        }
+
+        // Measure the length of the high pulse
+        uint32_t pulse_start = esp_timer_get_time();
+        while (gpio_get_level(DHT11_GPIO) == 1) {
+            vTaskDelay(pdMS_TO_TICKS(0.1));
+        }
+        uint32_t pulse_end = esp_timer_get_time();
+
+        // Determine if the bit is 0 or 1
+        uint8_t bit = (pulse_end - pulse_start) > 50 ? 1 : 0;
+        data[i / 8] <<= 1;
+        data[i / 8] |= bit;
+    }
+
+    // Parse the data
+    *humidity_int = data[0];
+    *humidity_dec = data[1]; // Decimal part (0–9)
+    *temperature_int = (data[2] & 0x7F); // Remove sign bit (0–50)
+    *temperature_dec = data[3]; // Decimal part (0–9)
+    *checksum = data[4];
+
+    // Validate checksum
+    uint8_t sum = *humidity_int + *humidity_dec + *temperature_int + *temperature_dec;
+    if (sum != *checksum) {
+        printf("Checksum failed! Retrying...\n");
+        vTaskDelay(pdMS_TO_TICKS(1000));
+        read_dht11(humidity_int, humidity_dec, temperature_int, temperature_dec, checksum);
+    }
+}
+
+
+void set_system_time_from_compiler() {
+    // Parse __DATE__: "Mmm dd yyyy"
+    char date[] = __DATE__;
+    char time[] = __TIME__;
+
+    struct tm tm = {0};
+    char month[4];
+    int day, year;
+    int hour, min, sec;
+
+    // Parse date
+    sscanf(date, "%3s %d %d", month, &day, &year);
+
+    // Parse time
+    sscanf(time, "%d:%d:%d", &hour, &min, &sec);
+
+    // Convert month abbreviation to number
+    const char *months[] = {"Jan", "Feb", "Mar", "Apr", "May", "Jun",
+                           "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};
+    for (int i = 0; i < 12; i++) {
+        if (strcmp(month, months[i]) == 0) {
+            tm.tm_mon = i;
+            break;
+        }
+    }
+    tm.tm_mday = day;
+    tm.tm_year = year - 1900; // Years since 1900
+    tm.tm_hour = hour;
+    tm.tm_min = min;
+    tm.tm_sec = sec;
+    tm.tm_isdst = -1; // Let system determine daylight saving time
+
+    // Set system time
+    struct timeval tv = { .tv_sec = mktime(&tm), .tv_usec = 0 };
+    settimeofday(&tv, NULL);
+}
+
+void print_current_time() {
+    time_t now;
+    struct tm timeinfo;
+    char strftime_buf[64];
+
+    time(&now);
+    localtime_r(&now, &timeinfo);
+    strftime(strftime_buf, sizeof(strftime_buf), "%Y-%m-%d %H:%M:%S", &timeinfo);
+    printf("Time: %s\n", strftime_buf);
+}
+
+void print_chip_info(){
+    /* Print chip information */
+    esp_chip_info_t chip_info;
+    uint32_t flash_size;
+    esp_chip_info(&chip_info);
+    printf("This is %s chip with %d CPU core(s), %s%s%s%s, ",
+           CONFIG_IDF_TARGET,
+           chip_info.cores,
+           (chip_info.features & CHIP_FEATURE_WIFI_BGN) ? "WiFi/" : "",
+           (chip_info.features & CHIP_FEATURE_BT) ? "BT" : "",
+           (chip_info.features & CHIP_FEATURE_BLE) ? "BLE" : "",
+           (chip_info.features & CHIP_FEATURE_IEEE802154) ? ", 802.15.4 (Zigbee/Thread)" : "");
+
+    unsigned major_rev = chip_info.revision / 100;
+    unsigned minor_rev = chip_info.revision % 100;
+    printf("silicon revision v%d.%d, ", major_rev, minor_rev);
+    if(esp_flash_get_size(NULL, &flash_size) != ESP_OK) {
+        printf("Get flash size failed");
+        return;
+    }
+
+    printf("%" PRIu32 "MB %s flash\n", flash_size / (uint32_t)(1024 * 1024),
+           (chip_info.features & CHIP_FEATURE_EMB_FLASH) ? "embedded" : "external");
+
+    printf("Minimum free heap size: %" PRIu32 " bytes\n", esp_get_minimum_free_heap_size());
+}
+
+void app_main(void)
+{
+    set_system_time_from_compiler();
+    printf("DHT11 temperature and humidity sensor read and send out\n");
+    print_chip_info();
+ 
+    while (1) {
+        uint8_t humidity_int, humidity_dec, checksum;
+        int8_t temperature_int;
+        uint8_t temperature_dec;
+
+        read_dht11(&humidity_int, &humidity_dec, &temperature_int, &temperature_dec, &checksum);
+
+        // Calculate humidity and temperature
+        float humidity = (float)humidity_int + (float)humidity_dec / 10.0f;
+        float temperature = (float)temperature_int + (float)temperature_dec / 10.0f;
+
+        // Print results
+        print_current_time();
+        printf("Humidity: %.1f%%\n", humidity);
+        printf("Temperature: %.1f°C\n", temperature);
+        printf("Checksum valid: %s\n", (checksum == (humidity_int + humidity_dec + temperature_int + temperature_dec)) ? "Yes" : "No");
+
+        // Wait 1 minute before next read
+        vTaskDelay(pdMS_TO_TICKS(5000));
+    }
+}