This code is the base of my self-developed "smart-home" temperature and humidity sensor based on an ESP8266 with the DHT11. The measurments are sent to a MQTT server.

The wiring is really easy. Powered is the ESP8266 with USB or by a power supply on the VIN pin. The DHT11 sensor works with 5V or 3.3V, so the VCC pin can be connected to the 3.3V output from the ESP8266 directly. The DATA pin of the DHT11 needs to be connected to a gpio of the ESP8266. A 10kOhm resistor between the DATA pin and VCC should be used to ensure proper communication. For my setup I use the gpio D5 for the DATA pin.

For the development and upload of the code I use platformio.

Because I use several ESP8266 for different rooms, I made the code variablized. The configuration can be set inside the file include/configuration.h. This is a blueprint of the configuration.h:

#define SSID "<your-ssid>"
#define WLAN_PASSWORD "<your-wifi-password>"

#define DHT_PIN <number-of-the-used-gpio>
#define DHT_TYPE <type-of-the-dht-sensor> // Possible values are DHT11 or DHT22

#define MQTT_SERVER "<mqtt-server-ip-or-dns>"
#define MQTT_HEALTH_TOPIC "<health-topic>"
#define MQTT_TEMPERATURE_TOPIC "<temperature-topic>"
#define MQTT_HUMIDITY_TOPIC "<humidity-topic>"

I use the following command to run the upload:

pio run -t upload && pio device monitor -b 115200

This also monitors the serial out.