I would like to write my own program for controlling sensors and actuators of Roomba i7. For previous robots it was possible with some minor hacks. Is there a way to flash an opensource firmware or a library to directly control the robot's behaviour?
No, unfortunately there is no way for a user to control the Roomba i7. Instead, you should use the Create 3.
Disclaimer: I work at iRobot where I am developing the next generation of consumer robots. However, my postings on this site are my own and don't necessarily represent iRobot's positions, strategies, or opinions.