no KL27; Y-cable news (was Re: Anelok: one more MCU - maybe an idea for later)

Werner Almesberger werner at
Sun Dec 28 18:46:41 UTC 2014

I wrote:
> KL27	32-QFN	256 kB	MKL27Z256VFM4	3.185

Oops, this one wouldn't do: the USB in KL27 (and relatives: KL17, KL43,
maybe more) is only device ("slave" as Freescale call it), not OTG.

Speaking of OTG, it seems that Y-cable research has made some important
breakthroughs since the last time I checked, and they have now caught
up with our needs. Here are a few cables that seem to be roughly
equivalent to the original Y-box:

- cheap, but cable is a bit short:

- a bit longer (19 + 30 cm):

- here's one from a reputable brand. Alas, it seem that they're
  replacing this one with a model that has a Micro USB 3.0 connector:

- one more, this time from eBay:

  Interesting detail: "does not support OTG phone or tablet charging".
  Hmm. VBUS not connected between USB A male and Micro B male ? That
  would suck.

  But then, they have some other peculiar ideas: "the disk must be
  formatted as FAT32." Must be one heck of a smart cable ! :)

- also available with angled Micro B:

Anyone care to get one of these critters and measure how it's
connected on the inside ?

It's interesting that they all are Micro B not Micro A. I wonder what
they do with the ID pin. But if the industry chooses to ignore AB and
just uses B for both roles, then I'll be the last to complain: while
the shield of a Micro B receptacle will reliably stop a reversed plug,
Micro AB - and I guess also Micro A - relies on a fragile-looking piece
of plastic for this.

Availability of Y-cables also means that developing the Y-box is less
important and we may end up not needing it at all.

- Werner

More information about the discussion mailing list