HDC1080 | GUILCOR SENSORS

HDC1080
Temperature sensors

High-accuracy humidity and temperature sensor optimized for low-power and high-reliability applications.

Measurement range
-40 / 125°C

Temperature accuracy
+/- 0,2°K

Humidity accuracy
+/- 2,0 % Rh

Resolution (Rh and T°)
14 bits

Power supply voltage
2,7 → 5,5V

Conversion time
6ms / 6,5ms

Typical current
1,2µA(active)

Price
Medium

What is a HDC1080 sensor ?

The HDC1080 is a high-precision digital temperature and humidity sensor designed by Texas Instruments to replace analog sensors or older models (HTU21D, SHT21, etc.).

With its ultra-low power consumption, 14-bit resolution, and metrological accuracy, it has become a standard in modern embedded environmental sensors.

Operating principle

The HDC1080 integrates:

a calibrated thermal diode for temperature,
a capacitive humidity sensor,
a 14-bit ΔΣ converter and a factory calibration EEPROM.

The conversion formulas are linear and simple:

T(°C) = (S_T × 165) / 65536 − 40

💡 Each measurement is automatically compensated for temperature and humidity.

Example of conversion

Raw measurement (hex)	Temperature (°C)	Humidity (%)
0x0000	−40,0	0,0
0x8000	+42,5	50,0
0xFFFF	+125,0	100,0

🧮 Resolution: 14 bits → 0.01 °C and 0.006 % RH per LSB.

Principle diagram (I2C connection)

+3.3V
 │
[HDC1080]
 │ SDA ─────────┐
 │ SCL ─────────┤── [I²C Microcontroller]
 │ GND

💡 Fixed address: 0x40 — identical to the HTU21D (therefore not stackable without a multiplexer).

Application areas

🌡️ Environmental IoT Sensors

🏠 Home Automation and Connected Air Conditioners

🧠 Ambient Condition Monitoring

🔋 Low Power Devices (batteries, wireless sensors)

🧪 Portable or Integrated Instrumentation

Should I choose a HDC1080 sensor ?

Strengths points

🎯 High precision calibrated factory
→ ±0.2 K and ±2 % RH, one of the best accuracy/energy ratios on the market.
🔋 Ultra low power consumption
→ Only 1.2 µA at 1 measurement/second, ideal for battery-powered IoT.
🧱 Robust and stable design
→ Fully digital sensor, insensitive to analog noise.
🧠 Direct replacement for the HTU21D/SHT21
→ Same packaging, same I²C protocol, simple migration.

Weaknesses points

📡 Fixed address (0x40)
→ It is impossible to connect multiple HDC1080s on the same bus without switching.
🌬️ Sensitive to condensation
→ Provide a hydrophobic filter in a humid environment.
💧 No built-in heating→ Unlike some Sensirion sensors, there is no automatic drying function.

Useful information

Here is some useful information regarding the HDC1080 sensors.

Main registers (I²C – address 0x40)

Adress (hex)	Name	Function
0x00	Temperature Register	Temperature lecture
0x01	Humidity Register	Humidity lecture
0x02	Configuration Register	Mode, resolution, low battery
0xFB	Manufacturer ID	TI Identifier (0x5449)
0xFE	Device ID	Sensor identifier (0x1050)
0xFF	Serial ID	Unique serial number

I²C Reading Example (pseudo-code)

// Temperature and Humidity Lecture
i2c_start();
i2c_write(0x40 << 1);
i2c_write(0x00);
delay(10);
i2c_start();
i2c_write((0x40 << 1) | 1);
MSB_T = i2c_read_ack();
LSB_T = i2c_read_ack();
MSB_H = i2c_read_ack();
LSB_H = i2c_read_nack();
i2c_stop();

S_T = (MSB_T << 8) | LSB_T;
S_H = (MSB_H << 8) | LSB_H;
temp = (S_T / 65536.0) * 165.0 - 40.0;
rh = (S_H / 65536.0) * 100.0;

✅ Exemple :

S_T = 32 000 → T = 40,5 °C

S_H = 36 000 → RH = 55,0 %

Typical integration diagram

3.3V ───────────┐ │ [HDC1080] │ SDA ───────┐ │ SCL ───────┤── MCU (Arduino, ESP32, STM32…) │ GND

💡 Provide pull-up resistors of 10 kΩ on SDA/SCL if not present on the board.

Configuration register bits

Bit	Name	Description
[13]	Battery status	1 = Low battery
[12]	Temp first	Measurement order (T before RH or vice versa)
[10:9]	Mode mesure	00 = RH 14b, T 14b / 01 = RH 11b / 10 = T 11b
[8]	Heater	1 = Heating ON (rarely used)
[1]	Acquisition mode	0 = Sequential / 1 = Individual