I am not posting an answer. I have researched this problem until I 'm almost tired of life. Firstly, why are there so many people who just do not seem to read and understand what others are writing , or trying to write about regarding this problem, then keep going on possibly this action will work or that item will solve it, the thread just goes on and on. For f***s sake.
YES the i phone 7 home button is digitally linked to the motherboard. You won't find how even if you have access to the many pay to use or download diagnostic and repair schematics. and softwares that are out there.
To all those that have successfully transferred an original i phone 7 into another replacement digitiser screen assembly, whether from Apple or a quality aftermarket supplier, you got lucky dude. 99% of the time the home button link to the system is disabled if it is ever disturbed.
A low current supply is permanently supplied to the circuit in the home button chip even when the phone is switched off. You will not ever find out how this supply works where it originates in the motherboard and where it routes through the rest of the system. You need Apples kit to reset everything at a cost that only you the customer can determine whether it is cost effective or not.
YES, it is a pain in the orifice. Its kick in the teeth as far as generating any continuing customer loyalty to Apple goes on the grounds of allowing cheaper repairs and replacements, especially as now the latast i phones X are costing as much as a second hand car. Its time to think about changing repair services to everything but Apple. After the last i phone 6 passes through my hands I'm done with them.