How can I connect an arduino to a raspberry pi via an HC 05 bluetooth module and transmit data?
I know this is old but to help out newcomers:
Here's a place you can begin https://create.arduino.cc/projecthub/millerman4487/view-serial-monitor-over-bluetooth-fbb0e5
The wiring depends on which arduino board you are using and the model of your HC-05 BT module. mine uses 4 pins VCC (5v) GND (ground) TX --&gt; TX and RX --&gt; RX
You should be able to google the wiring for your module, and connect to the raspberry pi after you install bluetooth on raspberry pi
sudo apt-get install bluetooth bluez blueman

sudo reboot

Navigate to new bluetooth interface in menu bar through

preferences
bluetooth

Add new device, turn arduino on with BT module plugged in and make sure your HC-05 module is blinking red, and you should see a pair connection named HC-05 on raspberry pi. Password is 1234