BME280 sensor: OSError [Errno 5]

Question

I recently bought a Raspberry Pi 4B along with a BME280 T/P/humidity sensor. I use the bme280 and smbus2 Python libraries to interface with the sensor. For a while it worked pretty well, but yesterday I started getting frequent OSErrors. Here is a bare minimum example that raises the error:

from smbus2 import SMBus

with SMBus(1) as bus:
    bus.pec = 1
    b = bus.read_i2c_block_data(0x76, 0xF7, 8)
    print(b)

Stack trace:

Traceback (most recent call last):
  File "/home/****/Tsensor/local/test.py", line 5, in <module>
    b = bus.read_i2c_block_data(0x76, 0xF7, 8)
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/****/miniforge3/envs/sensor/lib/python3.11/site-packages/smbus2/smbus2.py", line 617, in read_i2c_block_data
    ioctl(self.fd, I2C_SMBUS, msg)
OSError: [Errno 5] Input/output error

The output of sudo i2cdetect -y 1:

     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:                         -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
70: -- -- -- -- -- -- 76 --  

Note that the OSError is not always triggered. Sometimes I do get a valid output from this minimal example.

Any idea what could cause this behaviour?

Answer 1

set

dtparam=i2c_baudrate=100000 (or lower)

in /boot/config.txt

Answer 2

You have a poor I2C connection. Check that all the pertinent wires are secure and make a good connection. I.e. check power, ground, SDA, and SCL.