Is the in spec way of connecting a peripheral to a USB 2.0 OTG device, that the OTG device uses Micro 2.0 AB, and the peripheral Micro USB A?

Question

Is the in spec way of connecting a peripheral to a USB 2.0 OTG device, that the OTG device uses Micro 2.0 AB, and the peripheral Micro USB A?

So a keyboard with a USB-A-Male connector on it, should be adapted to Micro USB A?

I understand it to be the case that USB 2.0 OTG devices are meant to use Micro 2.0 AB, but go the cheap route and use Micro 2.0 B. And that Micro 2.0 AB, and Micro 2.0 A, are almost unknown to even most techies, as they are hardly seen. And most devices break spec e.g. Raspberry Pi Zero has a Micro USB2.0 B connector for USB OTG. And the Google Nexus 4 Smartphone as well as no doubt many others, has a Micro USB2.0 B connector on it. And the standard method people use is they then use a spec-breaking adaptor that converts Micro USB 2.0 B Female, to USB-A-female. (which I suppose isn't a disaster, so long as somebody doesn't use a gender changer- prob breaking spec -, to make an A-A cable and send 5V into a host that is sending 5V).

So let's suppose we pute aside that most USB 2.0 OTG devices break spec and have the spec breaking adaptor.

Suppose they go by the book and used Micro USB AB.

Is the spec-correct way to do things, to get Micro-USB A on the peripheral e.g. with an adaptor changing the plug on the end of the peripheral eg USB plug on the end of the keyboard, from male-USB-A, to male-Micro-USB A?

Answer 1

Is the in spec way of connecting a peripheral to a USB 2.0 OTG device, that the OTG device uses Micro 2.0 AB, ...

Your post doesn't make sense because you don't always indicate the gender of the connector (i.e. plug or socket).

The OTG port should use a (female) micro-AB socket in order to accept either a (male) micro Type A or B plug. But the typical micro-AB socket cannot detect whether the inserted plug is a Type A or a Type B; that would require some kind of switch or shape sensor. Instead it's the wiring of the ID pin that is actually used by the OTG port to determine which mode the port operates (as host or gadget).

The proper use of micro A or B plugs with OTG would conform to the USB2.x specification, and would confirm to the user the purpose of the cable. That is, a micro-A plug puts the OTG port into host mode, and a micro-B plug puts the OTG port into device/gadget mode. Of course the ID pin has to be wired to match the plug type, i.e. the electrical input should correlate with the physical plug.

But since the typical micro-AB socket cannot detect the type of plug inserted, and the OTG system relies instead on the ID pin state, apparently manufacturers often use a micro-B socket instead of a micro-AB socket.
As a consequence, a micro-A plug can no longer be used, and micro-B plugs have to be used for either host or gadget mode of the OTG port.
So the physical difference specified by type of plug is being ignored.

... and the peripheral Micro USB A?

Not necessarily.
A USB device (aka gadget) can use either a (male) plug or a (female) socket.
Since a USB device must connect to a USB host (which would have a Type A socket), a (male) plug would have to be of Type A (for a direct connection).
An example of this is a USB flash drive.
But if the USB device is too large to plugin directly into the host port, the USB device can use a (female) Type B socket and a suitable cable.
An example of this is a printer with a USB port, which would be of Type B.