Moto Droid Charging and Peripheral Cable

Note: This instructable will only work for the Motorola Droid.

The Motorola Droid is part of the new generation of smartphones that can frankly do anything. Think of something you want to do, and bam! there's a way to do that.

I'm the kind of person that likes to get the most out of things (to give you a quick idea, I've gone so far as to using the Droid and a Mini-Itx computer that I built and run in my room in conjunction to write Apps for the Droid on the Droid!). Then one day, I'm reading my RSS Feeds, and along comes this article in which some people were able to get a full sized keyboard and mouse working on the Phone! A couple of days later, I created a cable that worked as both a normal cable in addition to a peripheral cable.

This instructable is going to recreate those steps so that all Droid owners can enjoy the keyboard-y goodness!

To those of you who are Moto Droid owners, you may not just how awesome your phone is. Inside of the Droid is a chip that contains USB OnTheGo.

For those of you that may not know, USB OnTheGo (OTG) is a specification that supplements USB 2.0. This specification is meant to simplify the interaction between a device and its controller through the use of two modes: Host and Slave. The Host is in charge for initiating any and all requests for data, while the Slave can only respond to requests. The Host is also in charge of supplying power to the device.

So now that you know what it is, why should you care? Well, in the intro you found out that the Droid has the capability of being put into Host Mode. If you continued with this thought, you'd soon realize that if the Droid can be put into Host, it can act as a controller for USB devices!

What kinds? Currently, there are only drivers (the software link that communicates with the USB devices) for mice and keyboards, but frankly that was a surprise in and of itself, seeing as this is somewhat of a hack.

Enough talk. Let's build us the cable that will allow us to use a full sized keyboard on a phone!

The cable itself is fairly simple. All it is is a Male MicroAB to Female A cable, that has a simple push button connected to pins 4 and 5 to allow the Droid to switch modes.

Supplies:
  * Droid charging cable (or any cable that has a Male MicroUsb end)
      [Price: $2.24 @ DealExtreme]
  * Usb cable extension (your typical USB A Male to Female cable)
      [Price: $1.55 @ DealExtreme]
  * Push Button
      [Price: $0.35 @ Sparkfun]
  * Scissors
  * Solder (makes for solid connections)
  * Electrical Tape
  * A Sharp knife (an exacto-knife would do nicely) [Might not be needed, depending on your charging cable]
Optional:
  * Flux pen (helps with the soldering)
  * Hot Glue (to re-protect the wires)
  * Heat Shrink 3/8" (same)

Tools:
  * Soldering Iron with a Fine Tip (the fine tip really makes this that much easier)
  * Third Hands (not really required, but it makes things a lot more easier)
Optional:
  * Tweezers (for handling the small wires)
  * Glue Gun
  * Heat Gun

Cut the USB A wire in half, and give the wires inside some room to breathe. 

This can go two ways. The first way is if you happen to be fortunate enough to have a cable that has all five wires on the microUSB side. Mini to Micro USB cables will have all five wires already. If this is true, then simply cut the cable open, free up the wires inside, and go to the next step. Otherwise continue to figure out what needs to be done if there's only four wires.

Unfortunately, your MicroUsb end only has four wires, and things are going to need to get invasive. With the sharp knife, take the plastic rubber casing off of the MicroUsb end until you get access to the solder pads. Using some excess wire (for example, from the male end of the USB A cable), solder the extra wire onto the fifth pad.
Note: This step is usually the hardest, simply because the wire and the solder point is small and so is the wire. On the Motorola Cables, the solder point is directly on the pin, so the wire's "cover" must be completely removed.

Apologies: For the time being, I do not have any cables that have only four wires, so there are no pictures. I attempted to show the process with the cables that I have that already have five wires, but in the process I accidentally tore off the copper where the connectors were on.

Pushbuttons, at least the ones that I have, are special in that they have four pins. They are separated into two sides, and what the button does is bridge that side.

With the button that I used, the sides that are slightly longer are the ones that are connected (in the picture, pins 1 & 2 are connected, 3 & 4 are connected. When the button is pressed, all four pins are connected).

Flatten out the pins, and cut one off. The side that still has its connected pins will be for the ground signal, and the extra pin that will be activated with the button will go to pin 5 on the MicroUSB side.

Start soldering the voltage and ground wires. The voltage wire is straightforward, but the ground will require special attention. Solder the ground from the MicroUSB to pin 1 and pin 2 to the ground wire of the female USB A connector.

STOP: Once this is done, test to see if this works. Use an A to A USB cable to charge your Droid. If it starts charging, then continue, otherwise something went wrong.

So far, so good. Now, this step will depend if your MicroUSB cable had four or five wires. If it had four, then go on to the next part.

If your MicroUSB cable had five wires, unfortunately, continuing to solder will be difficult. At least with my connector, the colors didn't correspond correctly. This will require guessing and checking. Using your adapter in progress, choose two wires and wrap them together. Make sure they don't short with anything! Plug it into your Droid, and the other end to a computer nearby (with A to A cable), and try to mount your Droid on the computer. If it mounts, then horray! Solder those two wires together, and the last one to the remaining pin on the push button. Otherwise, if nothing happens, then disconnect from the computer, and try two different wires.

This is where you get a break. All of the wires are color coded, but if the data wires don't match, go back one step, and do Step Five for All Five Wires.

Solder the colored wires to each corresponding wire, and the extra wire that you hand soldered to the last pin on the push button.

Apologies: For the time being, I do not have any cables that have only four wires, so there are no pictures. I attempted to show the process with the cables that I have that already have five wires, but in the process I accidentally tore off the copper where the connectors were on.

There you go! You're new adapter in all of it's glory has been created! that's not to day that it's done though. Protecting those new connections is imperative if you want this to last for any amount of time.

Before you start using it, at the very least use some electrical tape on the connections. Once the tape is on, time to test!

Turn off your phone. Plug in the adapter and a USB keyboard. Press and hold the push button and turn on the phone. Release the button after the Moto logo disappears. Wait for the phone to startup. Go to some text input (search works fine), and type on the keyboard!

If it works, then congratulations! Otherwise, it's time to recheck that wiring.

In so far as protecting your new cable goes, it's pretty much up to you. You can go so far as using hot glue and head shrink, or just wrap it up in electrical tape. This is up to you.

Enjoy using your phone-puter!

PS: If you liked this and want it to become a standard feature on Android phones, go here and star the issue.

Initial inspiration/info: http://www.tombom.co.uk/blog/?p=124

The USB Spec: http://en.wikipedia.org/wiki/Universal_Serial_Bus

USB OnTheGo Spec: http://en.wikipedia.org/wiki/USB_On-The-Go

Female USB A to MicroUSB Schematic: http://sites.google.com/a/gowthamj.com/www/