This issue came up recently for a high profile new gadget that has made the transition from Micro-USB to USB-C in its latest version, the Raspberry Pi 4. See the excellent blog post by Tyler (aka scorpia): https://www.scorpia.co.uk/2019/06/28/pi4-not-working-with-some-chargers-or-why-you-need-two-cc-resistors/
The short summary is that bad things (no charging) happens if the CC1 and CC2 pins are shorted together anywhere in a USB-C system that is not an audio accessory. When combined with more capable cables (handling SuperSpeed data, or 5A power) this configuration will cause compliant chargers to provide 0V instead of 5V to the Pi.
The Raspberry Pi folks made a very common USB-C hardware design mistake that I have personally encountered dozens of times in prototype hardware and in real gear that was sold to consumers. …
How do USB Type-C™ chargers support older USB devices?
tl;dr: All new USB-C dedicated chargers must also support USB Battery Charging 1.2 Dedicated Charging Port (BC 1.2 DCP), a common charging method supported by the vast majority of devices from all manufacturers.
Ever run into a situation where you plug your older MicroB or Lightning port phone into a Type-C charger and nothing happens, or slow charging happens?
I was looking through some of the ECNs (Engineering Change Notices, or how the folks behind USB make changes to the specs) in the latest USB document bundle, and I noticed a document named, “USB Type-C ECN BC1.2 …
What does it mean when a cable is rated at 3A?
tl;dr : The USB Type-C™ spec has a quantifiable benchmark that cables must meet or exceed for wiring and connector quality.
I’ve been running into a different kind of bad cable lately, and I wanted to educate about the requirements and what that means practically.
According to the USB Type-C specification, all Type-C cables of any type must at a minimum be rated at 3A. This includes legacy A-to-C cables, uB-to-C adapters, C-to-C cables, and C-to-uB cables and all variants. …
Can Qualcomm QC and USB Type-C™ coexist on the same connector?
I get this question sometimes, so I wanted to do a quick post to address it. tl;dr : USB Type-C Spec forbids it.
Qualcomm’s QuickCharge 2.0 and 3.0 use variable voltage on Vbus in order to get more power over the same USB A-to-microB cables. My Nexus 6, for example, comes with a Motorola Turbo Charger which outputs at 5V, 9V, and 12V. QC 2.0 allows for up to 18W charging over an A-to-microB cable by using the combination 12V * 1.5A.
18W is no slouch, actually, and right now, that’s actually 3W more than the 15W that USB Type-C 3A charging can do. …
Why are there no USB Type-C Receptacle to USB Type-B plug or USB Type-A plug adapters?
tl;dr : Type-C spec forbids it, as such an adapter could allow a user to create unsafe conditions.
I’ve gotten this question several times, mostly from people trying to find small adapters so that they can switch their main chargers and cables to all Type-C but don’t have to buy another cable to charge their older Micro-B devices.
The answer is in the Type-C Specification, Section 2.2, with two sentences at the very end of the section.
“USB Type-C receptacle to USB legacy adapters are explicitly not defined or allowed. Such adapters would allow many invalid and potentially unsafe cable connections to be constructed by users.” …
What happens when you plug two USB Type-C™ host ports together with a C-to-C cable? Will something bad happen?
tl;dr: As long as both sides comply with the spec, nothing bad should happen!
As an addendum to my Configuration Channel post (https://firstname.lastname@example.org/usb-type-c-s-configuration-channel-31e08047677d), I wanted to answer the question above.
In the pre-Type-C world, just to review, USB hosts or power sources would all have USB Type-A ports, and devices would have USB Type-B. This makes it impossible for the user to accidentally plug two hosts together or two power supplies together. …
I’ve been getting questions about why certain kinds of USB adapters or cables work to charge new USB Type-C™ devices, and why other adapters are necessary to charge legacy devices from USB Type-C chargers.
This post will explain why and will do a deeper dive into USB Type-C’s Configuration Channel (CC).
USB Type-A and USB Type-B
But first, I will start out with a description of how USB worked before Type-C so that we all understand some of the basic concepts.
USB cables are directional, meaning that each end of a cable has physically different plug: Type-A plug (the rectangular port and plug we find on our PCs, hubs, and chargers), and a Type-B plug (the squareish plug, or the smaller mini-B and much more common micro-B variants). …