Update 8/15/2018 - Our Head of Engineering is currently in China working with our suppliers in the region to develop a patched firmware version for Stone that will resolve the intermittent charging issues seen on the newly released 2018 MacBook Pro (model identifiers MacBookPro15,1 and MacBookPro15,2). We are aiming to have further updates on or before 8/22/2018. Until then we still recommend users of the affected MacBook Pro models wait to purchase Stone until the firmware release has occurred. Prior MacBook Pro models remain unaffected.
We have become aware of a compatibility issue with Stone and the latest MacBook Pro models released on July 12th, 2018 (model identifiers MacBookPro15,1 and MacBookPro15,2) and are working on a downloadable firmware update to correct this issue going forward. Until then, we recommend users of affected MacBook Pro models wait to purchase Stone. All prior MacBook Pro models remain compatible with Stone.
So, what happened? From the outside, the new MacBook Pro models release in mid-July 2018 look familiar. However, Apple made significant internal changes, which unexpectedly affected Stone’s ability to charge the new MacBook Pro.
Before the advent of USB-C, USB was generally limited to supplying power at 5V and topping out at around 13W. This limited USB’s ability to power or charge current-hungry devices like computers, but also made it safe and inexpensive to deploy. Because of the lower power delivery levels, consumers didn’t have to worry about USB devices frying each other (again, in general).
USB-C is capable of safely delivering over 100W of power at multiple voltages, allowing for quick charge capabilities and support for high-power devices. USB-C devices that are capable of supplying more than 15W of power rely on a sophisticated handshake to adjust the voltage and current to correctly charge the connected device. Higher current applications, such as the 87W for the MacBook Pro, also require communication with the cable itself to make sure it can handle the extra power safely.
A component or section of code involved with this handshake was changed when Apple redesigned the new MacBook Pros, altering how Stone negotiates power delivery with the MacBook Pro and ultimately causing that process to fail. More often than not, this prevents power from being reliably delivered, shutting down the process and preventing the MacBook from charging. The good news is that knowing USB-C is an evolving standard, we designed Stone with user updatable firmware to give it the flexibility to adapt to unforeseen changes.
We are currently working with our suppliers and Apple to isolate the exact cause of the issue. Once that has been determined we will patch the firmware and conduct verification testing before distribution via our support site to Stone users. We will post additional progress updates on August 15th, 2018 or as they become available.