ESP32-C3 BMP280 Simulator: Wiring, Code and a Live Circuit
This is a BMP280 barometric pressure and temperature sensor wired to an ESP32-C3 DevKitM-1 over I2C, read live with the Adafruit BMP280 library: temperature, pressure and altitude once a second.
Four wires: 3.3 V, GND, SDA to GPIO 8 and SCL to GPIO 9. In the editor, drag the sensor’s pressure slider and the altitude moves with it.
- 3.3 V logic
- Library: Adafruit_BMP280.h
- I2C address 0x76
- SDA 8, SCL 9
Wiring the BMP280 to the ESP32-C3
Every connection in the circuit above, with the board’s own pin names.
| BMP280 pin | ESP32-C3 pin | Why |
|---|---|---|
| VIN | 3V3 | The BMP280 chip is a 3.3 V part; many breakouts have no regulator. |
| GND | GND | Common ground. |
| SCL | GPIO 9 | I2C clock. |
| SDA | GPIO 8 | I2C data. |
On the ESP32-C3, Wire.begin() uses GPIO 8 for SDA and GPIO 9 for SCL, the Arduino core’s choice; Wire.begin(sda, scl) moves the bus to any two other pins. The ESP32-C3 and the BMP280 are both 3.3 V parts, so this is the simplest wiring there is: no regulator and no level shifter.
Pins to leave alone on the ESP32-C3
GPIO 8 carries the onboard LED and GPIO 9 is the BOOT button, and both are also the default I2C pins. GPIO 2, 8 and 9 are strapping pins, and only GPIO 0 to 4 can read an analog voltage.
On a real bench
The ESP32-C3 DevKitM-1 is small enough to sit on one breadboard with room for the BMP280 beside it. Its USB port goes through a USB-to-serial chip; the cheaper SuperMini boards use the C3’s own USB, where Serial needs USB CDC on boot turned on in the IDE.
The code
The sketch the circuit above runs. Open it in the editor, change a line and press Run: it compiles in your browser.
#include <Wire.h>
#include <Adafruit_BMP280.h>
Adafruit_BMP280 bmp; // on I2C: SDA GPIO 8, SCL GPIO 9
void setup() {
Serial.begin(115200);
if (!bmp.begin(0x76)) {
Serial.println("No BMP280 at 0x76");
for (;;) {}
}
Serial.println("BMP280 found");
}
void loop() {
Serial.print("Temperature: ");
Serial.print(bmp.readTemperature(), 1);
Serial.print(" C Pressure: ");
Serial.print(bmp.readPressure() / 100.0F, 1);
Serial.print(" hPa Altitude: ");
Serial.print(bmp.readAltitude(1013.25), 0);
Serial.println(" m");
delay(1000);
}
bmp.begin(0x76) reads the chip’s ID and its factory calibration, which every reading needs. It returns false when nothing answers at that address; boards with SDO tied high answer at 0x77 instead.
readTemperature() is degrees Celsius and readPressure() is pascals, so dividing by 100 gives hectopascals, the unit weather reports use. readAltitude(1013.25) turns pressure into meters above the level where it would be 1013.25 hPa; give it your local sea-level pressure for a true altitude.
Serial.begin(115200) opens the serial monitor. Serial is UART0, at 115200 baud in this sketch.
Common mistakes with the BMP280 on the ESP32-C3
The wrong address
Adafruit’s own board answers at 0x77, the cheap purple ones at 0x76, and bmp.begin() with no argument tries 0x77. If it fails, try the other address before suspecting the wiring.
Powering it from 5V
A breakout without a regulator is a bare 3.3 V chip: 5 V on VIN can kill it. Use 3V3, which on this board is also the right level for I2C.
Confusing it with a BME280
The BME280 looks the same and adds humidity. A BMP280 reports a chip ID of 0x58, a BME280 0x60, and each library refuses the other. If begin() fails at both addresses, check which chip you have.
Questions and answers
Can I simulate a BMP280 with an ESP32-C3 DevKitM-1?
Yes. The circuit at the top of this page is an ESP32-C3 DevKitM-1 with a BMP280, running in your browser on a simulated ESP32-C3 (RISC-V). The temperature and pressure sliders set what the simulated chip measures, and the library applies the real calibration math to it. Press Run it in the editor to change the wiring or the code; it is free and needs no account.
Where does the BMP280 connect on the ESP32-C3?
On the ESP32-C3, Wire.begin() uses GPIO 8 for SDA and GPIO 9 for SCL, the Arduino core’s choice; Wire.begin(sda, scl) moves the bus to any two other pins.
How accurate is the altitude?
Pressure changes with the weather by more than it changes over a few floors, so readAltitude() is only as good as the sea-level pressure you give it. Relative changes over a few minutes are accurate to about a meter.
Can I use the BMP280 over SPI?
The chip supports SPI, but this simulated part speaks I2C. Most breakouts are wired for I2C out of the box anyway.
Build your own BMP280 project
Open this circuit in the editor, change the wiring or the code, and keep your version in a free account.