Answer
Part 1
Part 2
/ to continue, ...
Discussion, conclusion, and recommendation
/ to continue, ...
What next
/ to continue, ...
References
(1) Adafruit PCA9685 16-Channel PWM / Servo Controller Tutorial - Lady Ada
/ to continue, ...
Appendices
/ to continue, ...
Photos
/ to continue, ...
Schematics
/ to continue, ...
Figures
Figure 1 - Basic principles of L298N Dual Bridge DC Motor Driver
/ to continue, ...
End of Answer