Is an OTG cable 'special'? If so how does it differ from 'lesser' cables?

[Deleted member 103366]

I know that some USB cables are designed to pass ONLY power whilst other USB cables are desgined to pass both data and power. I also know that cables apparently differ in their the power and, where applicable, data transfer rates.
What I do not know and can not find is a clear statement as to whether a cable referred to as an "OTG cable" differs for a 'normal' 'power and data' cable. If an OTG cable does differ from a 'normal' power and data cable how does it differ?

 

[db4476]

I know that some USB cables are designed to pass ONLY power whilst other USB cables are desgined to pass both data and power. I also know that cables apparently differ in their the power and, where applicable, data transfer rates.
What I do not know and can not find is a clear statement as to whether a cable referred to as an "OTG cable" differs for a 'normal' 'power and data' cable. If an OTG cable does differ from a 'normal' power and data cable how does it differ?

USB OTG defines two roles for devices: OTG A-device and OTG B-device, specifying which side supplies power to the link, and which initially is the host. The OTG A-device is a power supplier, and an OTG B-device is a power consumer. In the default link configuration, the A-device acts as a USB host with the B-device acting as a USB peripheral.

It's a specification that's 20 years old now, modern USB cables follow that spec.

Cheers!

 

[Deleted member 103366]

Thank you db4476, I knew some of that but not, I think, the power stuff.
However, unless I am missing an implication, it does not, as far as I can see, address my question.
My question is, is a cable referred to as "an OTG cable" any different than a 'normal' USB data and power cable?
If so how do the two cables differ?

 

[Kilrah]

An OTG cable is one that provides a "device" side plug from a micro port that supports it. One pin in the micro port tells the thing it's plugged into that it should operate as a host instead of a device.

 

[Deleted member 103366]

So are you saying the internal wiring of an OTG cable differs from that of a 'normal' power and data cable?

That thought led me to this

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which suggests that in an OTG cable pin 4 of the micro USB (plug?) is jumpered to its pin 5 whereas, in a 'normal' micro USB (plug?) pin 4 is not connected to anything.
From elsewhere, in a USB-C OTG cable it appears there is a 5k to 10k resistor between two pins in the USB-C plug

If I am correct thanks for the pointer

 

[Kilrah]

Correct.

 

[CvCow]

USB OTG defines two roles for devices: OTG A-device and OTG B-device, specifying which side supplies power to the link, and which initially is the host. The OTG A-device is a power supplier, and an OTG B-device is a power consumer. In the default link configuration, the A-device acts as a USB host with the B-device acting as a USB peripheral.

It's a specification that's 20 years old now, modern USB cables follow that spec.

Cheers!

So not so universal after all.

 

[db4476]

So not so universal after all.

Let's expand on this a bit, USB On-The-Go (USB OTG or just OTG) specification has been around for a long time. It allows USB devices, such as tablets or smartphones, to act as a host, allowing other USB devices, such as USB flash drives, digital cameras, mouse or keyboards, to be attached to them. As an example, a mobile phone may read from removable media as the host device, but present itself as a USB Mass Storage Device when connected to a host computer.

USB OTG introduces the concept of a device performing both master and slave roles – whenever two USB devices are connected and one of them is a USB OTG device, they establish a communication link. The device controlling the link is called the master or host, while the other is called the slave or peripheral, and as of USB 3.0 they can switch roles with a bit of code. Not all cables sold as OTG will work, mainly because of inferior construction... Ask me how I know.

Some YouTube videos that show how to build an OTG cable are wrong, while they have the correct pinout the resistance and capacitance would not work in the USB 2.0/3.0 standard. One video claims to get 3 amps through the cable which USB 2.0 limit is .5 amps while USB 3.0 limits amps to .9, good luck on trying to get more than that from a laptop or tablet.

DJI allows your phone or tablet to be charged via the RC which may be a good idea for some pilots, but since my phone is almost never at a low charge that would affect the flight I'm not a big fan of it.

Hope this helps,
Cheers!

 

[Deleted member 103366]

But for a layman such as myself who is trying to understand if there is a difference between what I call the normal "data and power cable" and an ""OTG cable" then the simple answer is "yes, there is a difference" and yes I do need to be careful to buy the correct type of cable when an OTG cable is called for. That is all I wanted to know.

Given that those cables that I have, that allow a phone to use a cable connected external memory stick etc., bear no labelling to show that they are an "OTG" cable I was left wondering whether this OTG was a marketing ploy or hype. It is not.
The specification may have been around for 20 years and I have had a cable that allows my phone to connect to memory devices or a keyboard since 2014 but the first time I encountered the term OTG was last year when looking into splitter cables for the Mavic Mini controller.

 

[Andrew Coates]

Using the best OTG cable, you can now have unlimited access to your files with no hassle. This piece of wire has unique adapters that fit in your charging ports and USB storage devices.