# 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 |

 - [Datasheet ESP32-C3 Super Mini](https://www.espboards.dev/esp32/esp32-c3-super-mini/)
 - [Datasheet DHT11 Supplier](https://asairsensors.com/product/dht11-sensor/)
 - [Datasheet DHT11 Protocol](https://www.mouser.com/datasheet/2/758/DHT11-Technical-Data-Sheet-Translated-Version-1143054.pdf?srsltid=AfmBOoqtetK1e7kNT-24HGdKDaQMV55sFB9Yr4rK94icO4YI94qwFuFz)
 - [ESP IDF get started](https://docs.espressif.com/projects/esp-idf/en/v6.0/esp32c3/get-started/linux-macos-start-project.html)

### 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](https://docs.espressif.com/projects/esp-idf/en/v6.0/esp32c3/get-started/index.html)
- RISC-V toolchain (riscv32-esp-elf)
- Python 3.13+ with virtual environment

### Build Instructions

```bash
# 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`:
```c
#define DHT11_GPIO 0
```

To use a different GPIO, change this define and rebuild.

### Reading Interval

The sensor is read every 5 seconds:
```c
vTaskDelay(pdMS_TO_TICKS(5000));
```

Note: DHT11 requires at least 1 second between readings. Adjust as needed.

## How It Works

### DHT11 Communication Protocol

1. **Start Signal**: MCU pulls DATA line low for 20ms, then high
2. **Sensor Response**: DHT11 pulls line low for ~80μs, then high for ~80μs
3. **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)

4. **Bit Encoding**: Each bit starts with a ~50μs low pulse:
   - `0`: ~26-28μs high pulse
   - `1`: ~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:
```bash
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.

## Resources

- [DHT11 Datasheet](https://www.mouser.com/datasheet/2/718/DHT11-Technical-Data-Sheet-Translated-Version-1137654.pdf)
- [ESP32-C3 Documentation](https://docs.espressif.com/projects/esp-idf/en/latest/esp32c3/)
- [ESP-IDF Programming Guide](https://docs.espressif.com/projects/esp-idf/en/latest/esp32c3/api-guides/index.html)
