There are a lot of little details you need to think about when taking a project from PoC (proof-of-concept) to production. Most projects today have some form of onboard microprocessor and require you to flash your custom bootloader and/or program code onto it at some point. There are many ways this can be accomplished but the most common method is using an ICP (in-circuit programmer) connected to a 6-pin ICP header somewhere on the PCB.
