BMP280 Pressure Sensor with ESP32 and Arduino

What is BMP280 and in what projects is it used?

The BMP280 is a barometric absolute pressure sensor from Bosch Sensortec. The pressure piezoresistive element and the signal processing circuit inside the chip provide the raw value of pressure and temperature and the calibration coefficients specific to the same part from the digital interface. To reach the real value, the raw data must be compensated with the coefficients stored in the sensor memory; The library we use in this article performs this step.

Prediction of pressure changes, meteorological station, registration of relative height, detection of moving between floors and improvement of navigation are the main applications. The temperature of the BMP280 is measured primarily for pressure compensation and is dependent on the temperature of the chip and PCB itself; So don't replace it with an accurate ambient thermometer without checking the placement.

How to read the BMP280 datasheet correctly?

The difference between the raw chip and the BMP280 module

The limit of high voltages is related to the chip itself. The Adafruit BMP280 board pictured has a regulator and level shifter circuit, and according to the manufacturer's manual, works with 3-5V input and logic. Not all market modules have such a circuit; Having a base with a VIN or similar appearance is not sufficient proof. Before connecting 5V, check the schematic of the same board or parts of the regulator and Level Shifter.

In design with raw chip, Bosch for VDD and VDDIO capacitor 100 nF It is recommended near the bases. The CSB pin must be connected to VDDIO to select I2C. If CSB is detected Low at startup, the interface is locked in SPI mode until the next Power-on Reset.

Pins, I2C address and wiring with ESP32 and Arduino

The Arduino-ESP32 documentation says the default pin depends on the board; GPIO21 for SDA and GPIO22 for SCL are just the defaults of the Generic ESP32 board. In the code, specify the bases explicitly with Wire.begin(SDA_PIN, SCL_PIN). I2C lines require pull-up; Ready board may have these resistors.

On the raw chip, SDO gives GND the seven-bit address 0x76 and SDO gives VDDIO the address 0x77 and should not be left floating. Many libraries default to an address; If the sensor is not found, scan both.

Registers, Oversampling, Filter and Working Modes

No conversion is done in Sleep. Forced measures once and then automatically returns to Sleep; This mode is suitable for battery-consuming data loggers. Normal repeats the measurement cycle and Standby. Oversampling reduces more noise but increases conversion time and consumption. The built-in IIR filter is useful for removing short changes caused by wind or door closing, but it also slows down the actual response to rapid pressure changes.

Step-by-step setup in Arduino IDE

1. Select the correct ESP32 or Arduino board and port.
2. Install the Adafruit BMP280 Library and its recommended dependencies from the Library Manager.
3. Do the I2C wiring with common ground and check the allowable voltage of the same module.
4. First, run the I2C scanner inside the download package and see the presence of 0x76 or 0x77.
5. Upload the original code and turn on Serial Monitor 115200 baud open
6. Calibrate sea level pressure for project location and time; A generic constant value does not produce an exact height.

BMP280 practical code for ESP32 and Arduino

#include <Wire.h>
#include <Adafruit_BMP280.h>

#if defined(ESP32)
constexpr int SDA_PIN = 21;   // Generic ESP32 only
constexpr int SCL_PIN = 22;   // Generic ESP32 only
#endif
constexpr uint8_t BMP280_ADDRESS = 0x76;
constexpr float SEA_LEVEL_HPA = 1013.25f; // Replace with a local value

Adafruit_BMP280 bmp;

void setup() {
  Serial.begin(115200);
#if defined(ESP32)
  Wire.begin(SDA_PIN, SCL_PIN);
#else
  Wire.begin();
#endif
  Wire.setClock(100000);

  if (!bmp.begin(BMP280_ADDRESS, 0x58)) {
    Serial.println("BMP280 not found; check 0x76/0x77 and wiring");
    while (true) delay(10);
  }

  bmp.setSampling(
    Adafruit_BMP280::MODE_NORMAL,
    Adafruit_BMP280::SAMPLING_X2,
    Adafruit_BMP280::SAMPLING_X16,
    Adafruit_BMP280::FILTER_X16,
    Adafruit_BMP280::STANDBY_MS_500
  );
}

void loop() {
  const float temperatureC = bmp.readTemperature();
  const float pressurePa = bmp.readPressure();
  const float pressureHpa = pressurePa / 100.0f;
  const float altitudeM = bmp.readAltitude(SEA_LEVEL_HPA);

  Serial.print(F("T="));
  Serial.print(temperatureC, 2);
  Serial.print(F(" C | P="));
  Serial.print(pressureHpa, 2);
  Serial.print(F(" hPa | altitude="));
  Serial.print(altitudeM, 2);
  Serial.println(F(" m"));
  delay(1000);
}

Compile condition #if defined(ESP32) makes this file use explicit pins on ESP32 and I2C hardware pins, namely SDA/A4 and SCL/A5, on Arduino Uno. The serial output is also written with Serial.print so as not to depend on Serial.printf for some kernels.

Code Analysis: What does each section do?

• Wire.begin on the ESP32 starts the I2C bus with explicit pins and on the Uno with hardware pins; setClock(100000) also selects a conservative rate of 100kHz.
• bmp.begin(..., 0x58) specifies both the address and the expected identifier of the BMP280 control; In this way, BME280 or wrong fragment is not silently accepted.
• setSampling sets Normal, Oversampling and IIR modes according to the library's official sample.
• readPressure returns the compensated pressure in pascals; Dividing by 100 converts it to hectopascals.
• readAltitude Estimates altitude from the ratio of current pressure to sea level pressure. Entry SEA_LEVEL_HPA should be updated with local data.

Why is the height wrong and how to calibrate it?

Air pressure is not only a function of altitude; The weather changes it too. number 1013.25 hPa A standard reference pressure, not the actual pressure of all locations and days. For absolute altitude, enter the corrected sea level pressure from the local weather reference and the time. To measure short-term elevation change, you can take a reference at the starting point and report the difference.

If you know the location reference altitude accurately, the seaLevelForAltitude function in the Adafruit library can calculate sea level equivalent pressure from the measured pressure and known altitude. Perform the calibration after the system warms up and away from direct wind.

BMP280 common errors and troubleshooting

PCB design tips and mechanical installation

• Do not block the metal hole of the sensor with glue, protective cover or product body, and consider a ventilation path to reach the ambient pressure.
• According to the datasheet, at least 0.1 mm The empty space above the metal cap should be maintained and the liquid should not be in direct contact with the part.
• Strong light can affect the measurement; Keep the sensor port away from strong light source.
• Keep the sensor away from the regulator, processor, display, and high-current paths that generate heat or mechanical stress.
• capacitors 100 nF Place the recommended near VDD and VDDIO and keep the ground path short.
• For the new product, in addition to the technical specifications, record the status of Not recommended for new designs and replace BMP390 in the BOM.

Frequently asked questions

Detailed sources and follow-up

• Bosch BMP280 Official Datasheet, Revision 1.26
• BMP280 official product page and life cycle status
• Official MIT Licensed Adafruit BMP280 Library
• Adafruit BMP280 Board Official Guide
• Official documentation for I2C on Arduino-ESP32
• module photo source, lady ada, license CC BY-SA 3.0
• SHT31 training with ESP32 and Arduino
• DS18B20 training with ESP32 and Arduino
• Free course of sensors in 7 steps
• Sensors Learning Center at LCENJ

All technical numbers are adapted from Datasheet BMP280, Document BST-BMP280-DS001-26, Revision 1.26 (October 2021). Ready board specifications are only stated for Adafruit's documented model and do not extend to anonymous modules.