[Captivate Accessories] Fallon:
Required components

USB MicroB Plug Breakout Board

619k ohm resistor (car dock mode)

A USB cable of some kind to chop up, or another breakout board similar to the first item only female

1k ohm resistor (desk dock mode)

Soldering iron & associated supplies

A USB power source capable of supplying .75 amps (or more depending on how far you go)

Dock mode (car or deck)

To trip Car (or desk) mode all you have to do is put a 619k (1k for desk) ohm resistor between pins 4 & 5 on the Micro USB connector. Some people have managed to do this by chopping up a cable, but I couldn't with the cable or 2 I had around. The only appropriate solution I was able to find was a USB MicroB Plug Breakout Board which was pretty decent at $4 + shipping.

For just dock mode & no other usefulness (like actually charging), you can see what doing a poor job of jamming the resistor in there for testing gets us.

AC charging

In order to get "AC charging" which goes up to 750ma instead of "USB charging" which only goes up to 500ma, you merely need to short out the 2 data pins (pin 2/white & pin 3/green) on a normal USB cable. Most people find it easy to short them (the center 2) on the big flat rectangular end (Type A) of a normal USB cable. Given my approach with the breakout board I just soldered a jumper across the 2 data pins on the board.

Bringing it all together

To complete things, you just need to hook power up to the breakout board. Pin 1 (red) goes to VCC on the breakout board & pin 4 (black) goes to ground. Soldering on the ground is marginally more difficult due to the resistor already inhabiting the hole.

Now you have a cable with a soldered up circuit board on the end. If you plug this into a USB power supply capable of supplying 750ma or more, as soon as you plug it into the phone, it will charge at the maximum possible rate & trip car (or desk) dock mode. The USB debugging & USB drive mounting icons shouldn't show up either (I'm assuming due to shorting the data pins for AC charging mode).

Software

I use Setting Profiles to fiddle with settings or launch programs depending on conditions. I'm using the car dock trigger to do appropriate things such as turn on bluetooth & GPS kill WiFi, etc. You could also have it automatically launch the soso Samsung Car Dock app or Google Navigation.

Taking it further....

Given how the GPS sucks, I picked up a bluetooth GPS. I'm planning on mounting it to the back of my phone mount. Being rather anal I don't like piles & piles of cables running across my dash.

My solution is to modify my original setup. I've taken a 6" length of mini USB cable & cut away everything but the power cables (red & black). I also got a female micro USB breakout board. I stripped the insulation off of a little over an inch of the power wires. I ran the power wires through the VCC & ground holes on the female board & soldered them into the appropriate connections on the male micro USB board with the data pins shorted & the resistor. I then soldered the now trapped female micro USB board in place.

Here are some photos of the little abomination I soldered up. I then coated everything in some red liquid electrical tape to seal it & protect it for when I get around to the melted friendly plastic mounting cradle (in the next section). Sory about the blury photos, not that impressed with the Captivate's camera & had a hard time cleaning some of the smudges off the lens.

This setup should power/charge both the phone & BT GPS. With the phone pulling 750ma & the BT GPS pulling 500ma, you will need a power supply that is rated at at least 1.25 amps of output. The iPad chargers pump out 2.1 amps, so make good candidates.

Making it pretty & mounting it up

The whole unit will shortly be encased in plastic like jonagpa figured out over on Custom DIY Dock for phones with cases or extended batteries. That should support the fragile setup of boards I have soldered together.

I've picked up the Friendly Plastic & used it on another project to make a bushing to mount a pipe for a solar driveway light on a metal lawn spike. I'll be making the docking cradle here shortly. My only quandary at the moment is related to the mounting holes for my mounting my cradle to the suction cup on the windshield/dash. Will post an update when I make the dock.

Sources:

http://xdaforums.com/showthread.php?t=802937 (General dock/electrical stuff)

http://xdaforums.com/showthread.php?t=906630 (good info on building a custom plastic mount)

I'm not an electrical engineer or anything, just a geek, and these are my findings. I'm not responsible for you electrocuting yourself or your gear, which is a real possibility by playing with hatcheting up power cables & what not. I didn't really figure out much of this myself, just scrounged info off these forums & put it all together. Hopefully I linked to all the major sources of info I've found & used.