Non-compliant Pi 4 USB-C

Raspberry Pi 4 Model B.

Pi 4 Model B. © Raspberry Pi Foundation.

Mistakes happen to the best of us… With the all-new Raspberry Pi 4 Model B, the power connector has evolved into a USB-C (instead of a USB micro-B) because the new SoC is more energy-hungry. Unfortunately, there was a bug in the execution. People realized that the Pi 4 did not work with some chargers, especially the MacBook’s. Tyler Ward, a Southampton engineer, studied the mini-computer schematics and found the flaw in the design. The problem is that the charging port of the Raspberry Pi 4 shares a single 5.1 kΩ resistor between two of its pins, contrary to the official USB-C specification that says that each pin should have its own resistor. This non-compliant design breaks compatibility with high-end USB-C cables that are e-marked. These cables have an electronic chip that negotiates power management, data rates, and more. Since the Pi4 USB-C port is not properly wired, these smart cables will detect the computer as an audio adapter accessory and will not charge it. The solution to the problem is simply to use a charger with a non-e-marked cable, such as the official Pi 4 charger. The Raspberry Pi Foundation says that a new version of the card with a specifications-compliant charging port should be available in the “next few months” — probably after the first batch of cards has been sold.

The blog of Tyler Ward (aka scorpia), “Pi4 not working with some chargers (or why you need two cc resistors).”

Ars Technica, “Raspberry Pi admits to faulty USB-C design on the Pi 4.”

 

This entry was posted in Tech news in brief
by Laurent Gloaguen.
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