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  1. Thread Author  Thread Author    #1  
    JrrInTN's Avatar

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    Default What triggers Car Dock Mode?

    What is it that triggers the Car Mode on the Epic? I'm trying to determine if it's possible to have it automatically triggered using any of the "universal" car docks, or will only the Samsung dock trigger it?

    Here's why I'm asking: I've been using the Samsung OEM car dock along with Custom Car Home. It works great -- I really enjoy the fact that it automatically triggers the Car Dock Mode and starts Custom Car Home automatically. (BTW, I'm using it with a Motorola T501/505 bluetooth which works great IMHO to stream everything to FM.) So anyway, this works great for me because I'm not using a case. So now, I'd like to get a car dock for my wife's Epic as well, but she really wants to keep using a case as well. The only option would be a universal dock -- thus the question of triggering car mode.
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    heresy_fnord's Avatar

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    An alternative to a case is one of the invisshield products. It's like a screen protector except it goes over the entire phone. It comes in pieces of course but once you apply it, I imagine it would be thin enough that you could still use the Samsung docks while having your phone protected (at least from scratches).

    *EDIT* Also I don't know the answer to your question, sorry!
    Last edited by heresy_fnord; 03-03-2011 at 09:39 AM. Reason: Answering you actual question
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    I too would like to know how car mode is triggered.

    I've been over the back and sides of my Epic with a magnet trying to find a trigger spot since I understood that's how the Droid car and desktop cradles work.

    Can you tell if car mode is only triggered when you plug in the USB from the dock? If that's the case, I wonder if they are doing something funky with the resistance between the data pins on the USB?
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    HAAS599's Avatar

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    Custom car home app will trigger car dock mode when it is opened even if the phone is not in the dock or has anything plugged into it.

    I think any car app you get online or from the market will trigger car mode. I think it is a software thing and not any kind of magnet or hardware trigger.
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    Quote Originally Posted by HAAS599 View Post
    Custom car home app will trigger car dock mode when it is opened even if the phone is not in the dock or has anything plugged into it.

    I think any car app you get online or from the market will trigger car mode. I think it is a software thing and not any kind of magnet or hardware trigger.
    The point of the dock, though, is that it will automatically open Custom Car Home (or other car dock apps set as default) as soon as it's put in the car dock, and closes that program as soon as I remove it from the dock. Of course you can just start CCH from an icon and close it when you leave the car but it's definately much nicer when it opens and closes automatically as a mode when it senses the dock.

    Gotmarko, I was kindof thinking (and hoping as that might be easiest) that it might be a magnet. Guess not from your tests. It does only trigger when the usb is engaged, but doesn't matter if a power cord is actually attached to the dock. So, I guess it does make sense that it has something to do with the dock usb pinout. If so, I guess Samsungs dock really would be the only one that would automatically trigger it.
  6. #6  

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    I did some more searching (expanding from Epic to all Galaxy S phones) and found the answer in the XDA Forums.

    Connect a resistor between pins 4 and 5 of the micro-usb:

    Desk Dock: 365K (also works with 1K)
    Car Dock: 619K

    The full thread is here:

    Now to find the right resistor and do a bit of soldering on a cheap cable and see what happens
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    Awesome find! Looks like I'll have to try my hand at soldering up a micro usb as well. Hmmm... off to find that 619K resistor....
  8. #8  

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    Well, the whole micro usb thing was a fiasco last evening. I took a knife to one of the cheap micro usb cables and tried to free the connector. Cut through the black outer covering and found that the inside was also covered in more plastic (clear this time) that completely encased the soldered connections and wiring. Managed to break off the pin 3 connector trying to get the clear plastic covering off, so it's back to the store for another cable and another try. (While I don't need the pin 3 for data, having pins 2 & 3 tied together means the charger will be seen as a charging only circuit.)

    The soldering will be very interesting too, the connectors inside the outer housing were only about 1/16th of an inch wide and maybe 3/16th of an inch long.

    I didn't find any 619K resistors locally, so I've got 470K and 150K that I'll run in series and hope that it's close enough to 619K that it will work.
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    FYIW, I installed the resistor (bought from Digikey) using a "USB MicroB Plug Breakout Board" from Sparkfun. The breakout board made it very easy to solder in the resistor. That worked great -- triggers the car mode correctly. The only problem came when I took an old car plug, cut the usb end off and tried to solder those wires to the board. I don't think I got those flimsy wires soldered well because when I plug it in to the car, it seems to cancel out the car dock and not charge. Wiggling it works to get the charger working, so guess I just have to resolder it but haven't gotten a chance to do that though. Anyway, the resistor DOES work and the breakout board makes it an easy way to connect it up (at least the resistor.) I figure once I have it solid, I'll just cover it up with rubberized electrical paste or something to make it look nice and it should work well.
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    Quote Originally Posted by JRRinNC View Post
    FYIW, I installed the resistor (bought from Digikey) using a "USB MicroB Plug Breakout Board" from Sparkfun. The breakout board made it very easy to solder in the resistor. That worked great -- triggers the car mode correctly. The only problem came when I took an old car plug, cut the usb end off and tried to solder those wires to the board. I don't think I got those flimsy wires soldered well because when I plug it in to the car, it seems to cancel out the car dock and not charge. Wiggling it works to get the charger working, so guess I just have to resolder it but haven't gotten a chance to do that though. Anyway, the resistor DOES work and the breakout board makes it an easy way to connect it up (at least the resistor.) I figure once I have it solid, I'll just cover it up with rubberized electrical paste or something to make it look nice and it should work well.
    What value resistor did you end up using?

    Bill
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    Quote Originally Posted by androidguy916 View Post
    What value resistor did you end up using?

    Bill
    619K.
  12. #12  
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    Default Re: What triggers Car Dock Mode?

    Unless you are doing military spec standards, the "common" resisters usually have a plus or minus 10% value (also available in plus or minus 5% and 1%) so if you go to RadioShack and buy resisters, they usally are in a five pack, you get what poster 8 used and test different combos of those two resister values unless you can find a single resister close to 619k with a ohm meter to get an exact 619k OR get a variable resister to get it right on.

    Don't forget to zero out the leads of your volt/ohm meter if you want it exact, but I doubt it is that tight on tolerance.
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    Default Re: What triggers Car Dock Mode?

    [edited] Looks like pin 4 on the micro USB is used as an analog sense pin into the phone. A resistor is connected between this pin and pin 5, which is ground. Resistor value seems to be dependent on manufacturer. As pin 4 is normally not connected to a wire, it requires cutting the connector apart to get at the pin.
    Last edited by BikerRay; 08-29-2013 at 11:48 AM.

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