A type of USB connection that acts as a host or master to slave connections. It first came to Android (officially) in 3.1, and now it's fairly standard across devices. It's what lest you use mice, keyboards, cameras, controllers, and (if rooted) thumb drives or externally powered hard drives.
It also kicks *** because it's a standard, using a standard connection instead of a proprietary model, found in things like an iPad camera connector kit. Standards are good.
What this guide is (and isn't)
This is a guide to building your own USB On-The-Go cable from crap you might already have in your desk drawer. Don't order any of these cables to make your own -- instead order a cable from Amazon for a buck.. It will look nicer and there less chance to burn and cut yourself.
This is not a guide for people who don't like to build and or break stuff. You'll need tools. You'll need a soldering iron. You'll need very sharp knives. For the love of all things holy, pay attention to what you're doing, and be sober while playing with these stabby burny things.
If you're going to continue anyway, awesome. Welcome to my world, where ordering stuff is never the answer when you have drawers full of things like old USB cables. You'll need:
A soldering iron
Some tape and or heat shrink tubing. The cheapest electrical tape you can find.
A very sharp, thin knife. Xacto's are perfect.
Something to cut a cable and strip some wires with.
Something to pry the casing away with. A tiny straight screwdriver works great.
A microUSB cable. Like the one that came with your phone or tablet. But don't ruin a good one -- order a cable from Amazon instead.
A USB extension cable. One with one male and one female end. Again -- order an OTG cable from Amazon before you ruin a good one.
Grab this end of your microUSB to USB cable.
Follow the seam on each side and cut away the plastic outer shell. If you are scavenging a USB cable from LG be careful -- there's a tiny circuit board there and it will wiggle and break the solder joint on all the connections. Don't cut yourself.
Once cut, fold back the two halves of the casing and see if the connector body will slide down the cable. If it does, push it away. If it doesn't, cut it off. You'll see some silicon over all the connections, and maybe a metal connector shell (LG cables have the body in this picture). Carefully carve away the dried silicon and use a small screwdriver or dental tool to open the metal shell if there's one there. This is almost as sharp as the knife. Be careful. If yours has this metal casing, open it, pull it out, and throw it away.
Here's the fun part. Your connector will have five pins, but only four wires attached. Your job is to attach the black wire to pin 5 (where it's attached now) and to pin 4 (the empty one). For those interested, the pinout is:
Pin 1 -- VCC (red)
Pin 2 -- Data - (white)
Pin 3 -- Data + (green)
Pin 4 -- ID (none for USB pass through, grounded for OTG) (black)
Pin 5 -- GND (black)
Solder in a jumper however you like. I like to pull the black lead off of pin 5 and fold it back, then solder a pigtail to pin 4 and pin 5. Make a joint a bit back from the connector itself where these two pigtails connect to the black wire you pulled from pin 5. This way you aren't trying to solder two wires to one tiny little pin. Be sure you don't accidentally bridge any pins together (they are pretty close) or it won't work. I don't think you could short it and release the magic blue smoke, but better safe that sorry -- so keep things clean when soldering. You'll end up with an ugly mess, sort of like this:
The important thing is to make sure the solder joints are good, and nothing is touching.
Protip: if you use an iron that's too hot, the plastic will melt into the solder. If you melt too much plastic, you'll have to find another cable.
If you have a multimeter, you can cut the other end off the cable now and ring out the connections to make sure they are all good and not shorting. If you don't, look it over really well, and when satisfied grab your electrical tape and wrap it up. If you listened and used really cheap "plasticky tape" you need to pull it tight when wrapping so it gets hard when it cools down. You sparkys know what I'm talking about -- expensive tape stays flexible. Use the cheap stuff and get a nice, firm shell over your connector. It will look like this:
Now to work on the other end.
Cut the male end off of both cables. Strip back about two inches of the cable jacket n the long ends (toss the male ends in the round file), and match up the colors. If your colors don't match remember the pinout from above and bust open that male end to check the pins. Wire from pin to pin instead of color to color. Your colors will probably match. Solder and tape up this end just like you did above. When you're done, grab a cheap USB mouse and plug it in
Keyboards and controllers will probably work out of the box. To use a pen drive, you'll need either support from your device's ROM or to be rooted and use an app. Grab from Google Play. Plug in a USB stick, read the screen:
Say yes, then select "mount" in the stickmount app and wait for the magic. Your drive will be mounted in /sdcard/usbStorage/sda1 in any file browser:
You can store music, movies, porn, or anything you desire on the thumbdrive. Any size will work. Go wild with it. When you're done, unmount it from the notification shade and then unplug it.
Nothing works! -- check your soldering and connections.
I have power, but no data -- check your soldering and connections
I can't mount a USB stick -- Get root and install StickMount
It's cheaper to just buy a cable! -- Yep. But not nearly as fun and buying another cable doesn't use crap in my desk drawer.
I see. I've already bought a couple of USB OTG cables, so I don't really need another one, but I've just got what must be the smallest USB microsd reader it is possible to make (the card slot is on the underside of the USB connector pins) so if I solder it directly to a microUSB plug I'll hopefully be able to cut down the size of what I need plugged in to get extra external storage.
Nice step by step instruction. As seen in multiple replies you did not say to buy a cable from Amazon enough times or is it like usual, people too lazy to read before they reply?
I agree there are times I like to try to do things for myself with left over stuff and using my free time to try something useful and/or learning something.
I have got a tablet that has only one mini usb port used for both charging and connecting devices (pen drive and dongle). Serious problem arises when charge exhausts during surfing and I have to quit it to connect charger. I have tried to build one OTG *** charger myself by cutting an OTG midway and attaching a male usb cable ( only VCC, Red and GRND, Black). But its not working as it is doing only one work at a time. If I connect the charger first then it charges the device and doesn't recognize a slave and if I connect a slave fist it detects it but does not charge. Where is the problem and why? Please tell how I can make it.