Robot not doing what we need it to, and printfs aren't working

[Joe Ross]

In your tank function, you don't set any PWM values, therefore the PWMs will still be what they were before the function was called. When you first turn the robot on, it won't move. Once the PWMs get set in the mecanum function, they will continue with the same value once you start calling the tank function again.

In the mecanum function, the calculations can very easily overflow a char. You'll need to protect against that. I don't know if that is the only problem, but it will definitely cause you problems.