How to Use Barometric Pressure Sensor - BMP180 Breakout (GY-68): Examples, Pinouts, and Specs

The BMP180 is a digital barometric pressure sensor designed for high-precision atmospheric pressure and temperature measurements. It is widely used in applications such as weather stations, altimeters, GPS navigation systems, and environmental monitoring devices. The BMP180 is compact, energy-efficient, and communicates via I2C or SPI interfaces, making it easy to integrate into microcontroller-based projects.

The GY-68 breakout board simplifies the use of the BMP180 by providing necessary supporting components, such as pull-up resistors and a voltage regulator, allowing it to operate with a wide range of microcontrollers, including the Arduino UNO.

• Operating Voltage: 1.8V to 3.6V (3.3V recommended for BMP180; GY-68 supports 5V input)
• Communication Interface: I2C (default) or SPI
• Pressure Measurement Range: 300 hPa to 1100 hPa (altitude: -500m to 9000m)
• Pressure Resolution: 0.01 hPa
• Temperature Measurement Range: -40°C to +85°C
• Temperature Resolution: 0.1°C
• Power Consumption: 12 µA (typical in ultra-low power mode)
• Dimensions: 21mm x 18mm (GY-68 breakout board)

The GY-68 breakout board has 4 pins for easy interfacing:

Note: The BMP180's I2C address is 0x77 by default.

1. Wiring:

   • Connect the VIN pin to the 5V output of your microcontroller (e.g., Arduino UNO).
   • Connect the GND pin to the ground of your microcontroller.
   • Connect the SCL pin to the I2C clock pin of your microcontroller (A5 on Arduino UNO).
   • Connect the SDA pin to the I2C data pin of your microcontroller (A4 on Arduino UNO).

2. Install Required Libraries:

   • Use the Adafruit BMP085/BMP180 library for Arduino. Install it via the Arduino Library Manager:
     • Go to Sketch > Include Library > Manage Libraries.
     • Search for "Adafruit BMP085 Unified" and install it.

3. Arduino Code Example: Below is an example code to read pressure and temperature data from the BMP180:

   #include <Wire.h>
   #include <Adafruit_Sensor.h>
   #include <Adafruit_BMP085_U.h>
   
   // Create an instance of the BMP180 sensor
   Adafruit_BMP085_Unified bmp = Adafruit_BMP085_Unified(10085);
   
   void setup() {
     Serial.begin(9600);
     // Initialize the BMP180 sensor
     if (!bmp.begin()) {
       Serial.println("Could not find a valid BMP180 sensor, check wiring!");
       while (1); // Halt the program if the sensor is not detected
     }
   }
   
   void loop() {
     sensors_event_t event;
     bmp.getEvent(&event);
   
     if (event.pressure) {
       // Display pressure in hPa
       Serial.print("Pressure: ");
       Serial.print(event.pressure);
       Serial.println(" hPa");
   
       // Calculate and display altitude (assuming sea level pressure = 1013.25 hPa)
       float seaLevelPressure = 1013.25;
       Serial.print("Altitude: ");
       Serial.print(bmp.pressureToAltitude(seaLevelPressure, event.pressure));
       Serial.println(" m");
   
       // Display temperature
       float temperature;
       bmp.getTemperature(&temperature);
       Serial.print("Temperature: ");
       Serial.print(temperature);
       Serial.println(" °C");
     }
   
     delay(2000); // Wait 2 seconds before the next reading
   }
   

• Power Supply: Ensure the GY-68 breakout board is powered with 3.3V or 5V. Do not exceed 5V input.
• Pull-Up Resistors: The GY-68 includes onboard pull-up resistors for the I2C lines. Avoid adding external pull-ups unless necessary.
• Altitude Calculation: The altitude calculation assumes a standard sea-level pressure of 1013.25 hPa. Adjust this value for more accurate results in your location.
• Temperature Compensation: The BMP180 internally compensates for temperature variations, ensuring accurate pressure readings.

1. Sensor Not Detected:

   • Cause: Incorrect wiring or I2C address mismatch.
   • Solution: Verify the connections and ensure the I2C address is set to 0x77.

2. Inaccurate Readings:

   • Cause: Incorrect sea-level pressure value or environmental interference.
   • Solution: Update the sea-level pressure value in the code to match your location. Minimize electrical noise near the sensor.

3. Temperature Readings Seem Off:

   • Cause: Heat from nearby components affecting the sensor.
   • Solution: Place the sensor away from heat sources and ensure proper ventilation.

4. No Output on Serial Monitor:

   • Cause: Serial communication not initialized or incorrect baud rate.
   • Solution: Ensure Serial.begin(9600); is called in the setup() function and the Serial Monitor is set to 9600 baud.

• Can the BMP180 measure altitude directly?

  • No, the BMP180 measures pressure, and altitude is calculated based on the pressure and a reference sea-level pressure.

• What is the maximum cable length for I2C communication?

  • The maximum length depends on the pull-up resistor values and the I2C clock speed. For standard setups, keep the cable length under 1 meter to avoid signal degradation.

• Can I use the BMP180 with a 5V microcontroller?

  • Yes, the GY-68 breakout board includes a voltage regulator and level shifters, allowing it to interface with 5V systems.

By following this documentation, you can successfully integrate the BMP180 sensor into your projects for accurate pressure and temperature measurements.