The Raspberry Pi four was introduced two weeks in the past as a serious new improve to the road of low-cost single-board hobbyist computer systems. The Pi four featured a quicker CPU, choices for as much as 4GB of RAM, and a brand new, fashionable USB-C port for energy supply. The Pi four was the Raspberry Pi Basis’s first ever USB-C system, and, properly, they screwed it up.

As detailed by Tyler Ward, the Raspberry Pi four has a non-compliant USB-C charging port and does not work with as many chargers because it ought to. Because of the open nature of Raspberry Pi (even the schematics are on-line!), Ward was in a position to uncover that Raspberry Pi simply did not design its USB-C port appropriately. Two “CC” pins on a USB-C port are supposed to every get their very own 5.1K ohms resistor, however Raspberry Pi got here up with its personal circuit design that permits them to share a single resistor. This isn’t a compliant design and breaks compatibility with a few of the extra highly effective USB-C chargers on the market.

Whether or not your USB-C charger works with the Pi four has to do with whether or not it makes use of an “e-marked” cable. E-marked cables are absolutely featured USB-C cables with chips inside that negotiate energy administration, accent modes, information charges, and different communication specs. For the reason that Pi four USB-C port is wired incorrectly, these good cables will detect the Pi four as an “Audio Adaptor Accent” and refuse to cost them. Normally, e-marked cables are dearer and include bigger, higher-powered objects, like a USB-C laptop computer.

Benson Leung, an engineer at Google and one of many Web’s foremost USB-C implementation specialists, has chimed in on the Pi four’s USB-C design too, with a Medium submit titled ” design a correct USB-C™ energy sink (trace, not the best way Raspberry Pi four did it).”

“As an alternative of attempting to give you some intelligent circuit,” Leung writes, ” designers ought to merely copy the determine from the USB-C Spec precisely [emphasis his]. The Determine four–9 I posted above isn’t merely a tough guideline of a technique of constructing a USB-C receptacle. It’s really normative, that means obligatory, required by the spec to be able to name your system a compliant USB-C energy sink. Simply copy it.”

The Pi four shouldn’t be the primary high-profile system to get the USB-C spec mistaken. The Nintendo Swap additionally has a non-compliant USB-C port and has points with sure USB-C cables because of this.

After experiences began popping up on the Web, Raspberry Pi cofounder Eben Upton admitted to TechRepublic that “A wise charger with an e-marked cable will incorrectly establish the Raspberry Pi four as an audio adapter accent and refuse to supply energy.” Upton went on to say, “I anticipate this can be fastened in a future board revision, however for now customers might want to apply one of many instructed workarounds. It is shocking this did not present up in our (fairly intensive) subject testing program.”

The “instructed workarounds” are to only use a non-e-marked cable, just like the official Pi four charger.

We reached out to Raspberry Pi about this challenge and have been instructed a board revision with a spec-compliant charging port must be out someday within the “subsequent few months.”


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