Douwe Ravers
dfaff67fab
reads data every 15 minutes saves data persistently every 24h writes out the contents every measure. goes in deep sleep so very low power consumption. (reason removal task system)
DHT11 Temperature & Humidity Sensor for ESP32-C3
ESP-IDF project that reads temperature and humidity data from a DHT11 sensor and prints it to the serial console.
Overview
This project reads data from a DHT11 digital temperature and humidity sensor using the ESP32-C3 microcontroller. It implements the DHT11 communication protocol in software, reads sensor values every 5 seconds, validates the checksum, and displays:
- Current date and time (derived from compile time)
- Chip information (model, cores, features, flash size, silicon revision)
- Humidity percentage with 1 decimal place
- Temperature in Celsius with 1 decimal place
- Checksum validation status
Hardware Requirements
| Component | Details |
|---|---|
| Microcontroller | ESP32-C3 |
| Sensor | DHT11 (AM2302) |
| Connection | Single wire + pull-up resistor |
| Data Pin | GPIO 0 (configurable in main/main.c) |
| Resistor | 4.7kΩ - 10kΩ pull-up between VCC and DATA |
Wiring Diagram
DHT11 ESP32-C3
VCC ------ 3V3
DATA ----- GPIO0
GND ------ GND
Add a 4.7kΩ pull-up resistor between VCC and DATA pin.
Supported Targets
| ESP32 | ESP32-C2 | ESP32-C3 | ESP32-S2 | ESP32-S3 |
|---|---|---|---|---|
| ❌ | ❌ | ✅ | ❌ | ❌ |
Project Structure
dht11_reader/
├── CMakeLists.txt # Project configuration
├── sdkconfig # Build configuration
├── main/
│ ├── CMakeLists.txt # Main component configuration
│ └── main.c # Application source code
└── README.md # This file
Setup & Build
Prerequisites
- ESP-IDF v6.0
- RISC-V toolchain (riscv32-esp-elf)
- Python 3.13+ with virtual environment
Build Instructions
# Activate ESP-IDF environment
source "$HOME/.espressif/tools/activate_idf_v6.0.sh"
# Navigate to project
cd temperature_measure
# Build the project
idf.py build
# Flash to device (replace PORT with your serial port)
idf.py -p /dev/ttyUSB0 flash monitor
Configuration
The DHT11 data pin is defined in main/main.c:
#define DHT11_GPIO 0
To use a different GPIO, change this define and rebuild.
Reading Interval
The sensor is read every 5 seconds:
vTaskDelay(pdMS_TO_TICKS(5000));
Note: DHT11 requires at least 1 second between readings. Adjust as needed.
How It Works
DHT11 Communication Protocol
-
Start Signal: MCU pulls DATA line low for 20ms, then high
-
Sensor Response: DHT11 pulls line low for ~80μs, then high for ~80μs
-
Data Transmission: 40 bits of data (5 bytes) in the following format:
- Byte 0: Humidity integer part
- Byte 1: Humidity decimal part
- Byte 2: Temperature integer part
- Byte 3: Temperature decimal part
- Byte 4: Checksum (sum of bytes 0-3)
-
Bit Encoding: Each bit starts with a ~50μs low pulse:
0: ~26-28μs high pulse1: ~70μs high pulse
Checksum Validation
The checksum byte should equal the sum of the first 4 data bytes. If validation fails, the reading is retried after 1 second.
Output Example
Time: 2024-04-24 22:30:00
This is esp32c3 chip with 1 CPU core(s), WiFi/BLE, silicon revision v0.4, 4MB embedded flash
Minimum free heap size: 283488 bytes
Humidity: 45.2%
Temperature: 23.5°C
Checksum valid: Yes
Troubleshooting
Common Issues
| Issue | Solution |
|---|---|
| No sensor readings / checksum fails | Check wiring: DATA to GPIO0, pull-up resistor present |
| Build fails with missing component | Run idf.py fullclean then rebuild |
driver/gpio.h not found |
Ensure esp_driver_gpio is in PRIV_REQUIRES |
Linker errors with .riscv.attributes |
Your toolchain may be too new; use ESP-IDF 6.0 compatible version |
Debug Mode
To enable debug output:
idf.py monitor
Hardware Connection Check
Verify your wiring with a multimeter:
- GPIO0 should read HIGH when idle (via pull-up)
- 3V3 is supplying power
- GND is properly connected
Technical Details
- Sensor Range: 0-50°C temperature, 20-90% humidity
- Accuracy: ±1°C temperature, ±1% humidity
- Sampling Rate: 1Hz maximum (1 reading per second)
- Resolution: 1° C, 1% humidity
License
This project is provided under the CC0-1.0 license (public domain). See the SPDX identifier in the source file.