See a video review on youtube: https://youtu.be/8PkSbzESU-4
The Product code generator add-on is developed to generate a product code very easy. On add-on settings page you specify a template for code generator. It can be any number of digits and letters in a different sequence. The code is automatically generated from a template when creating, editing (can be disabled clicking the check box) and importing products. If you already have products without a code, you can fix it with one click to generate product codes.