🛠 Lire un capteur I2C (BME280) sur le bus

Objectives

Implement I2C on the Orange Pi PC: enable the bus, scan addresses with i2cdetect, then read a BME280 temperature/pressure/humidity sensor in Python. You will also discover that the board already has an internal I2C device: the CPU voltage regulator SY8106A, on the R_I2C bus (secondary bus) at address 0x65 — proof that the I2C stack works even without anything connected.

Hardware

• Orange Pi PC running Armbian, 5 V / 2 A power supply (DC jack)
• BME280 sensor (module with 3.3 V regulator recommended)
• Dupont cables: VCC→3.3 V, GND→GND, SDA→SDA pin, SCL→SCL pin
• sudo apt install i2c-tools python3-smbus

Complete Code

1. Enable I2C (armbian-config > Hardware > Overlays > i2c) and scan:

sudo sed -i 's/^overlays=.*/& i2c0/' /boot/armbianEnv.txt && sudo reboot
i2cdetect -l                 # lister les bus
i2cdetect -y 0               # balayer le bus 0 : le BME280 répond 0x76 ou 0x77

1. Python reading (ID register + simplified raw data):

#!/usr/bin/env python3
"""bme280_lut.py — lecture bas niveau d'un BME280 sur Orange Pi PC."""
import smbus, time

BUS, ADDR = smbus.SMBus(0), 0x76     # 0x77 si ADDR du module câblé à VCC

def main -> None:
    chip_id = BUS.read_byte_data(ADDR, 0xD0)
    print(f"Chip ID : 0x{chip_id:02X} (attendu 0x52)")
    # Configuration forcée en mode capteur (datasheet BME280, registre 0xF4)
    BUS.write_byte_data(ADDR, 0xF4, 0x27)   # x1/x1 oversampling, mode normal
    time.sleep(0.1)
    for _ in range(5):
        # Température brute (registres 0xFA-0xFC) — conversion simplifiée
        msb, mid, lsb = BUS.read_i2c_block_data(ADDR, 0xFA, 3)
        adc_t = (msb << 12) | (mid << 4) | (lsb >> 4)
        t_c = (adc_t / 16384.0 - 50.0)       # approximation linéaire, hors compensation
        print(f"ADC temp : {adc_t:6d}  ->  ~{t_c:5.1f} °C (non compensé)")
        time.sleep(1)

if __name__ == "__main__":
    main

For exact compensated values, install the adafruit-circuitpython-bme280 library (pip3).

Expected Verification

i2cdetect displays a grid with 76 (or 77) occupied. The script prints Chip ID : 0x52, followed by 5 lines of temperature. On the internal R_I2C bus, a dedicated scan would show the SY8106A regulator at 0x65.

Common Errors

• Bus not enabled by overlay: i2cdetect -l shows no bus — reboot after modifying armbianEnv.txt.
• Powering the module with 5 V on a 3.3 V sensor without a regulator: risk of destruction (3.3 V logic on the H3).
• Wrong address (0x76 vs 0x77): the module has an ADDR jumper; run i2cdetect first.
• SCL/SDA swapped: the scan returns an empty grid without an explicit error.