A Google engineer says some discount USB Type-C converter cables are substandard and could cause damage by drawing too much juice.
One of the big advantages of the USB Type-C design is never again having to guess which way up the plug has to be to fit in its hole; the other advantage is power transmission.
A Type-C 1.1 laptop, phone or other device can draw up to 3A, although it should lower this to between 0.5A and 1.5A when connected to an older power source, such as a USB 2.0 Type-A charger.
Googler Benson Leung has been doing some testing and the results are alarming: some cheaper converter cables and adapters are allowing too much current to flow through them.
"I have started reviewing USB cables on Amazon because I have gotten fed up with the early cables from third-party vendors that so blatantly flaunt the specification, and I want to hold them to task," he wrote on Google+.
"You may not just get weird behavior from your devices with these bad cables ... What some of these vendors are doing is downright dangerous."
The problems stem from manufacturers not complying with the interface's specifications, specifically the use of resistors: a 56kΩ pull-up resistor should be connected to the Vbus pin to signal that one end of the cable or converter is a legacy USB device that can't handle a 3A current draw.
Some converters do not feature this pull-up. So, for example, a Type-C gadget could attempt to draw 3A from a USB 2.0 host or charger via one of these dodgy cables, and cause damage to the wiring and electronics.
Leung has taken to publishing reviews on Amazon for USB Type-C cables using the name LaughingMan, and the results have been no laughing matter. Of the 13 cables tested so far, only three were up to spec on power – but even then, some of the highly rated cables weren't fully compatible with USB Type-C when it came to data rates, due to the use of USB 2.0 cabling.
Understandably, Leung used his new Google Chrome Pixel laptop and Nexus smartphone for the tests. He has published Linux commands that can be used to test the efficacy of cables, along with the results needed to know that the hardware will perform as expected.
Cabling is a contentious issue in the industry, in part because unscrupulous vendors have tried, and succeeded, to skin consumers for massively expensive HDMI cables. Now the same trick appears to be in play for USB Type-C, so buyer beware. ®