An unique, real-world look at the sensory buttons Apple developed for the phone 15 Pro

Project Bongo originally included haptic buttons on the iPhone 15 Pro and iPhone 15 Pro Max.
Apple’s project to create haptic buttons for the iPhone 15 Pro never materialized. Here’s how they looked, and what Apple scrapped on the way to a final product. Early prototypes of the iPhone 15 Pro Max and iPhone 15 Pro had haptic power and volume buttons. They were developed under the codename Project Bongo. These mysterious haptic button were widely rumored, but they had never been seen in actual hardware. AppleInsider obtained exclusive images of a prototype iPhone 15 Pro Max equipped with Project Bongo by speaking to a collector who collects Apple prototypes. We also received many details about the buttons and the user experience compared to standard mechanical buttons. The device in question was an EVT-stage iPhone 15 Pro Max prototype, also known as D84 during its development period and codenamed “Veyron.” Apple’s haptic button was the last feature to be included in the EVT prototypes for the iPhone 15 Pro or iPhone 15 Pro Max. The feature was removed abruptly from the iPhone 15 Pro and iPhone 15 Pro Max in early April 2023. Software-wise, the EVT prototype is running an InternalUI build iOS 17. This means that the device contains a specialized version of the iPhone operating systems used by Apple engineers internally for development and test purposes. Apple changed the iPhone 15 Pro by replacing its haptic buttons in the CRB and DVT prototyping stages. The CRB-stage, DVT-stage and later prototypes for the iPhone 15 Pro or iPhone 15 Pro Max have no exterior differences from their mass-production counterparts. This makes them less appealing to collectors. The Action button, a multi-purpose mechanical button that can be configured by the user and is located above the volume buttons, was also modified during development, though to a lesser extent. The Action button, which was developed alongside the haptic power and volume buttons, only received minor changes to its overall shape. It became more round and wider. The Action button was always a mechanical switch, even though it was developed along with the haptic power and volume buttons. This is why it was kept more or less the same. According to AppleInsider’s interview with the prototype collector, the Action button behaves different from the unified button on the EVT protoype discussed earlier. Apple’s canceled mechanical buttons compared to the haptic ones The haptic button originally planned for the iPhone 15 Pro is similar to mechanical buttons in that they both move when pressed. When the device is turned on, the haptic power and volume buttons emit a clicking noise when pressed. AppleInsider was informed that the iPhone 15 Pro and iPhone 15 Pro Max had a unified button for volume during the EVT stage. The unreleased buttons produce haptic feedback both when the button is pressed and immediately after it is released. Apple was likely trying to mimic the feedback and noise that mechanical buttons produce. This is similar to how the Magic Trackpad functions. Apple’s Project Bongo was not included in the final mass-production units, but the EVT device that is referenced throughout the article gives a good idea of what might have been. We were told the device accurately reproduces the tactile feedback and sensation created by mechanical buttons. The buttons will still move if the device is turned off and the charge indicator cannot be displayed due to a fully discharged battery. However, they will not provide any haptic feedback. In short, no power, no click. Apple’s Taptic Engine was used to simulate the vibration of a physical home button on the iPhone 7. The button never moved, unlike the Bongo buttons that Apple originally developed for the iPhone 15 Pro. When an iPhone 7 is powered down, the solid-state home buttons never vibrate or move. The iPhone 15 Pro Max EVT’s haptic buttons move and provide haptic feedback even when the device is powered down. People familiar with the issue claim that the Bongo-type button used dedicated firmware containing references to “deep sleep” modes. This deep sleep mode may have been activated when the device was turned off or was inactive for a long time. The collector we spoke with also said that the buttons responded even when touched by a gloved hand or used inside a pocket. The buttons can detect changes in pressure even without direct skin contact. Apple’s Bongo Project hardware components and how they worked. Apple’s Project Bongo achieves this by carefully designing hardware. The button detects the pressure by using strain gauges and flexures. This causes a change in resistance to occur within an electrical circuit. This resistance change is measured and a signal sent to the main logic boards (MLB) indicating that the button has been pressed. The iPhone 15 Pro EVT-stage prototypes featured a haptic button that was slightly smaller than what is found on mass-production models. Flexures and strain gauges are used to detect pressure changes in specific areas of a unified volume button. The iPhone could still tell whether the user wanted to increase or decrease the volume, even though it was only a single button. After touch and location are interpreted, the main logicboard powers the components that produce haptic feedback. Apple created a reluctance engine that is electromagnetically driven for the Bongo Project. This motor is known as the “Bongo Haptic Engine.” The Bongo Haptic Engine is an electromagnetic reluctance engine, consisting a ferromagnetic coil and a copper core, which together form a solenoid. It produced haptic feedback in the same way as the regular Taptic Engine, by oscillating with respect to an attraction plate underneath. Apple’s previous hardware upgrades were reflected in the Bongo Haptic Engine. The iPhone 4s was equipped with a Linear Resonant Actuator (LRA), resulting in a reduction of noise and improved response times. Apple introduced the Taptic Engine in the iPhone 6s to provide a haptic LRA. This LRA has been used ever since. The earliest known designs of the Bongo project date from 2021, two year before the release the iPhone 15 Pro. The project’s goal was to replace the iPhone’s traditional mechanical buttons by an updated design that featured improved haptic technologies. Apple may also have wanted to reduce mechanical buttons’ inherent failure rate by implementing a new technology. The iPhone 7’s home button was water and dust resistant because it did not have moving parts. The Bongo buttons are not the same, which indicates that this was not a priority or goal in the development. The Bongo module design combined the two separate volume controls into a single pill-shaped button with an indentation at the middle to indicate volume up and down. Early prototypes of iPhone 15 Pro featured a volume arguably similar to the original iPhone. The haptic button that was originally planned for the iPhone 15 Pro was abruptly canceled early April 2023, at the EVT stage. Apple changed this only with the iPhone 4, when it added a dedicated volume up/down button. Apple makes visual changes to its iPhones to help them stand out. This is done in order to make them stand out from the previous generations, while still maintaining the overall visual identity of the iPhone. The iPhone 15 Pro was designed to have a new look and feel for its buttons. It introduced titanium as a housing material. Apple has produced many different iPhone models over the years, but every model until the iPhone 15 Pro had separate volume buttons. The company reportedly tried to change this for its 2023 flagship in order to differentiate it, but ultimately scrapped the idea. How did the cancellation of the Bongo project affect iPhone 16? AppleInsider learned from people familiar with the situation that Robert Rivers Ingersoll worked on the haptic button for the iPhone 15 Pro. Ingersoll has a doctorate of mechanical engineering from Stanford University, according to his LinkedIn page and personal site. Apple’s haptic buttons were triggered by the Bongo Haptic Engine. Ingersoll was responsible for the Haptic Engine on the iPhone and Apple Watch. Before working at Apple, Ingersoll studied and analyzed hummingbirds’ and bats’ flight and hovering. The exact reasons behind the cancellation of the Bongo Project are still unknown, but it was reportedly scrapped due to unresolved issues with the project and unsatisfactory results in testing. Before the cancellation, the Bongo style haptic buttons had been planned to be included on the entire iPhone 16 line. The Bongo design was eventually phased-out, and more recent prototypes for the iPhone 16 feature a new capacitive Capture button. AppleInsider has been informed by sources familiar with the situation that the button was developed under the codename Project Nova. The capacitive buttons are expected to be on the same side of the power button as the power button but lower. This indicates that it’s likely a button related to cameras. The Capture Button was first revealed in September 2023. It features capacitive technology and pressure-sensing. According to a January 2024 report, the button is able recognize gestures. Users will be able swipe left or right in order to zoom in or out. Apple’s iPhone 16 lineup will feature many upgrades, including the Capture Button. The iPhone 16 range, which is scheduled to debut in 2024 in September, will feature a new chip A18 with a vastly improved neural engine. The base model iPhone 16 will likely have a vertical camera setup.