Plenty of people bemoaned Apple’s choice to drop the 1/8″ headphone jack from the iPhone 7. [Scotty Allen] wasn’t happy about it either, but he decided to do something about it: he designed a custom flex circuit and brought the jack back. If you don’t recognize [Scotty], he’s the same guy who built an iPhone 6 from parts obtained in Shenzhen markets. Those same markets were now used to design, and prototype an entirely new circuit.
The iPhone 7 features a barometric vent, which sits exactly where the headphone jack lived in the iPhone 6. The vent helps the barometric pressure sensor obtain an accurate reading while keeping the phone water proof. [Scotty] wasn’t worried about waterproofing, as he was cutting a hole through the case. The vent was out, replaced with a carefully modified headphone jack.
The next step was convincing the phone to play analog signals. For this, [Scotty] used parts from Apple’s own headphone adapter. The hard part was making all of this work and keeping the lightning port available. The key was a digital switch chip. Here’s how the circuit works:
When no headphone is plugged in, data is routed from the iPhone’s main board to the lightning port. When headphones are plugged in, the data lines are switched to the headphone adapter. Unfortunately, this means the phone can’t play music and charge at the same time — that is something for version 2.0.
The real journey in this video is watching [Scotty] work to fit all these parts inside an iPhone case. The design moved from a breadboard through several iterations of prototype printed circuit boards. The final product is built using a flexible PCB – the amber-colored Kapton and copper sandwiches that can be found in every mobile device these days.
Making everything fit wasn’t easy. Two iPhone screens perished in the process. But ultimately, [Scotty] was successful. He’s open sourced his design so the world can build and improve on it.