Reading Sensors over I2C with Raspberry Pi

I2C is a two-wire protocol letting you chain multiple sensors on two GPIO pins. BME280, SSD1306 displays, and RTC modules all use I2C.

Enable I2C

sudo raspi-config
# Interface Options > I2C > Enable

Wiring

Multiple I2C devices share the same SDA/SCL — each has a unique address.

Detect Devices

sudo apt install i2c-tools -y
sudo i2cdetect -y 1

Shows addresses of all connected devices (e.g. 0x76 for BME280).

BME280 Temperature/Humidity/Pressure

pip install adafruit-circuitpython-bme280

import board
import adafruit_bme280.basic as adafruit_bme280

i2c = board.I2C()
bme280 = adafruit_bme280.Adafruit_BME280_I2C(i2c)

print(f"Temperature: {bme280.temperature:.1f} C")
print(f"Humidity:    {bme280.humidity:.1f} %")
print(f"Pressure:    {bme280.pressure:.1f} hPa")

SSD1306 OLED Display

pip install adafruit-circuitpython-ssd1306 pillow

import board, adafruit_ssd1306
from PIL import Image, ImageDraw

i2c = board.I2C()
oled = adafruit_ssd1306.SSD1306_I2C(128, 64, i2c)
img = Image.new("1", (128, 64))
draw = ImageDraw.Draw(img)
draw.text((0, 0), "Hello World", fill=255)
oled.image(img)
oled.show()

Multiple Devices

Each I2C device needs a unique address. If two devices share an address, use a TCA9548A I2C multiplexer.