Making autonomous computer vision based drones? Need help with setting up flight controller?

Hi, So I want to make an autonomous drones with implementation on of some selected SLAM algorithms. I just want the drone to send me images and IMU values for sensor data merging (visual inertial methods). I want to use a pixhawk (the cheaper one) with a raspberry pi/ Asus tinkerBoard for this purpose. I have the following questions:

  1. How to setup pixhawk (flashed with px4) with a companion computer?
  2. This page suggests using px4 firmware with a raspberry pi? Does that mean the raspberry pi will be working as a flight controller or I’ll need to connect a px4 based FC?
  3. What is cheapest board you can suggest me to use for this project? I’ve tried my luck with APM 2.8 but that was a waste of money.

You might want to try plowing through the relevant documentation in the user guide https://docs.px4.io/v1.9.0/en/getting_started/index.html as well as in the dev guide https://dev.px4.io/master/en/index.html

For robotics/offboard applications, start here https://dev.px4.io/v1.9.0/en/robotics/ and read all of the documentation, it might help you make a more informed choice.

For flight controllers, take a look at the options here https://docs.px4.io/master/en/flight_controller/