USB confusion

[jimrob233]

My Asus 7 tablet has a micro USB socket. If I use a micro to standard female adaptor with a short lead, I can then connect a USB flash drive or download pictures from my camera using a mini to standard USB cable.

I thought a shorter lead to the camera would be nice, so I bought a mini to micro cable. With this neither device can see the other.

I also have a micro to standard female adaptor in a single lump of plastic. This won't work with the camera or the flash drive. I have two adaptors with a short length of cable - both work with no problems.

I can't find any electrical fault with any of the cables or adaptors and I presume that the phenomenon is something to do with type A/B compatibility and the fifth pin. Is there a USB expert who can enlighten me?

 

[northpaw]

I'm no expert, but I think the issue you have run into is that the cable has to be compatible with the "USB-Host" function (so does the tablet, but yours obviously does because it does work with some cables).

A number of the short cables out there with male micro on one end and a female standard end on the other have this, but other types of cables often do not. If you still have the package the cable that works came with, it will probably say USB-Host on it somewhere, perhaps in smaller print. I don't know if any of the small modular connections are made with USB-Host functionality, but that is what you would look for on the packaging or description.

 

[jimrob233]

What's confusing me is that all the different combinations of cables and adaptors appear to join the same pins on the micro and mini sockets. I'd love to know what the electrical difference is between "USB host" "OTG" etc, but I can't find a definitive guide on the internet.

 

[Musing]

Don't know if this will be of any help or not but thought I would pass it on.

What is the difference between USB On-The-Go (OTG) and USB Host Mode?

 

[jimrob233]

It seems the difference is whether pin 4 on the micro end of the cable is grounded or open circuit. I think I'll open a factory in China making micro USB connectors with a switch on them.