Linux device driver for the 4-pin variant (I2C only) of the BME280
- Append
bme280to/etc/modulesto load at boot
Enable in raspi-config and install tooling if it doesn't exist
sudo apt-get install i2c-tools i2c-dev
To check that it's working:
sudo i2cdetect -y 1
sudo apt update && sudo apt full-upgrade
sudo apt-get install gpiod libgpiod-dev libgpiod-doc
# Sanity check
sudo gpiodetect # Prints info. The chip with 8 lines is the one we want
sudo gpioset --mode=signal gpiochip1 4=1 # Pull GPIO4 high until SIGINT
On the Pi make sure kernel headers are in /lib/modules/<uname -r>/, or, installing via apt:
sudo apt-get install linux-headers
And locally have a .envrc file that looks like (with your own settings):
export REMOTE_SSH_ALIAS=pi
export REMOTE_DIR=/home/eltonlaw
Running make rsync will rsync over the entire current working directory, compile and reload the module. This assumes the Pi is configured with ssh and tmux is installed.
./x.py start
./x.py stop
./x.py restart # Helper to run `stop` then `start`
Current progress, logs written to systemd journal. Here's some output from a python script with the associated logs
# <<LOAD MODULE>>
# Jul 09 18:56:33 raspberrypi sudo[6808]: pam_unix(sudo:session): session opened for user root by d0nkrs(uid=0)
# Jul 09 18:56:33 raspberrypi kernel: BME280 - Stopping device driver
# Jul 09 18:56:33 raspberrypi kernel: BME280 - Removing cdev1 from system
# Jul 09 18:56:33 raspberrypi kernel: BME280 - Unregistering char device 240
# Jul 09 18:56:34 raspberrypi kernel: BME280 - Initializing device driver. kernel=4.19.118-v7+,parent_process="insmod",pid=6817
# Jul 09 18:56:34 raspberrypi kernel: BME280 - Assigned major number=240
# Jul 09 18:56:34 raspberrypi kernel: BME280 - Allocating cdev
# Jul 09 18:56:34 raspberrypi sudo[6808]: pam_unix(sudo:session): session closed for user root
# Jul 09 18:56:34 raspberrypi kernel: BME280 - Initialized successfully
file = open("/dev/bme2800")
# Jul 09 18:56:34 raspberrypi kernel: BME280 - `open` called
f.read() # ret: ''
# Jul 09 18:56:34 raspberrypi kernel: BME280 - `read` called, count=8192
# Jul 09 18:56:34 raspberrypi kernel: BME280 - data=[57 8],copied=0
f.read() # ret: ''
# Jul 09 18:56:34 raspberrypi kernel: BME280 - `read` called, count=8192
# Jul 09 18:56:34 raspberrypi kernel: BME280 - data=[0 51],copied=0
f.read() # ret: ''
# Jul 09 18:56:34 raspberrypi kernel: BME280 - `read` called, count=8192
# Jul 09 18:56:34 raspberrypi kernel: BME280 - data=[78 90],copied=0
f.close()
# Jul 09 18:56:34 raspberrypi kernel: BME280 - `release` called
# Jul 09 18:56:34 raspberrypi kernel: BME280 - unregistering i2c_client
Portions of code taken directly from/inspired by Linux Device Driver by Jonathan Corbet, Alessandro Rubini, and Greg Kroah-Hartman which has graciously been published online in its entirety and the up-to-date examples by Javier Martinez Canillas et. al from which the Makefile and more portions of code are taken from.