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DIY docks & hacking docks tripping dock mode & AC charging mode

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Fallon
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(Last edited by Fallon; 19th July 2012 at 04:38 PM.) Reason: Additional info found
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Default DIY docks & hacking docks tripping dock mode & AC charging mode

Update: Desk dock resistor value found & additional connector sources found thanks to mikejr83

I went through all of this with my Captivate a year or 2 ago, and figured it might be nice for Galaxy S 3 owners as well. You can see the history at http://forum.xda-developers.com/show...php?p=12169590

Dock mode

Samsung phones will trip their dock mode when they sense a resistor of a particular value between the ID (pin 4) & Ground (pin 5) pins on the micro USB connector
  • Car mode - 619k ohm (Validate on my Galaxy S 1 & Galaxy S 3)
  • Desk mode - 365k ohm (confirmed finally thanks to mikejr83 cracking open the SGS3 dock his wife got him. 1k ohm for SGS1 & 1k or 365k for the SGS2)

Parts
  • The only appropriate solution I was able to find (a year or 2 ago messing with my old Captivate) was a USB MicroB Plug Breakout Board which was pretty decent at $4 + shipping.
  • mikejr83 found some slightly different micro USB connectors at Digi-Key ($0.66 each + reasonable shipping, $2 is the minimum Digi-Key order) and on E-bay (10 for $4 + $1 shipping) as well.
  • The Zenis SGS2 dock fits the SGS3 reasonably well & runs about $10 on Ebay (free shipping, but it takes about 2 weeks to come over from asia), It does not trip dock mode & just has micro USB passthrough connectors. According to this XDA thread it's easy to pull appart & looks to be very hackable.
  • Chopping up a micro USB connector will not work, they only have 4 wires & the pin #4 you need access to is buried inside the connector at the end so far you have to destroy the whole connector to get to it
  • I have a roll of maybe a couple hundred 619k resistors I picked up from a local electronics recycler in my Captivate days. I might start packaging em up and selling them off after I get back from DEFcon if anybody is interested & having a hard time finding them.



For just dock mode & no other usefulness (like actually charging), you can see what doing a poor job of jamming the resistor in there on the Spark Fun breakout board for testing gets us (photo of my old Galaxy S1 because I'm to lazy to get dig it up and transfer the photos if I take any of my Galaxy S 3 showing the same thing).



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.

For my first (and only properly documented) dock build I used Friendly Plastic. Technically called Polycaprolactone it's really easy to work with and melts at around 60 degrees Celsius (140 F), also known as almost the temperature of the dash of my grey truck on a 70-80 degree day.... Oops. It would make a good desk dock, but not a car dock.

Commercial docks & potential mods for them

Given the dirt cheap Infuse dock I picked up I probably won't be working on another car dock unless I decide to put a case on my phone making it not fit in the dock. I have some oven bake modeling clay I'll probably try for that.

At $10-15 it's hard to beat the Zenis dock. On the 2nd page somebody cracked it open and the micro-USB plug looks very similar to the SparkFun one. I don't believe it trips any dock mode, but soldering in the appropriate resistor would be pretty easy. I hope to find the value to trip Desk or Media center dock mode & use Tasker to turn off E-mail and other non-essential noise during the night so as to not roust the wife.

Further information needed

If anybody has any more resistor values for various dock modes or other information to add, let me know.
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KeithLM
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Can you do both car mode and AC mode at the same time? And any idea if that would be a bad idea off a USB port that's built into a car?
 
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Can you do both car mode and AC mode at the same time? And any idea if that would be a bad idea off a USB port that's built into a car?
Standard USB is rated up to 500ma.
AC mode is rated up to 750ma.

You need to make sure your power supply is rated to at least 750ma to safely trigger AC mode. You will have to check with the manufacturers specs on what that USB port is rated for. You can trigger AC mode and any of the dock modes at the same time (verified on my old SGS1 Captivate and I'm 99% sure the SGS3 is the same), they don't use the same pins.

If you are plugging into anything that actually expects data (USB port on a stereo as opposed to just a USB charger) I would disconnect the data (center 2) pins from that end, leave them shorted at the phone end.
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Thanks for the info. My car reportedly has an extra USB port behind the dash I was hoping to use, but I can't locate it. So I might have to resort to using a power adapter. If I do that I'll use the 2.1A model from monoprice.com. So I'll use the power option based on which port I end up using.
 
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Let me make sure I'm getting this straight: Using the two values for resistance you have you were only able to get the S3 to trigger into car dock mode, correct? There could possibly be another value which triggers desk dock mode.

My thought would be to get a rheostat and chop up a micro USB cable and adjust the level of resistance till the effect was achieved. Obviously I may have to get more than just a rheostat to achieve the correct range of resistance to try, but eh...

Once I figured out the resistance level I could then make a "desktop dock cable" by placing the resister inline in the micro USB cable. That would be a great solution for me. Thoughts?
 
Fallon
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Let me make sure I'm getting this straight: Using the two values for resistance you have you were only able to get the S3 to trigger into car dock mode, correct? There could possibly be another value which triggers desk dock mode.

My thought would be to get a rheostat and chop up a micro USB cable and adjust the level of resistance till the effect was achieved. Obviously I may have to get more than just a rheostat to achieve the correct range of resistance to try, but eh...

Once I figured out the resistance level I could then make a "desktop dock cable" by placing the resister inline in the micro USB cable. That would be a great solution for me. Thoughts?
The SGS1 resistor value for car dock worked on the SGS3, no luck with the desk dock resistor.

Resistors are used in that location for non dock stuff too... Jigs to trigger bootloader and recovery mode, etc. I wouldn't try the rhestotat thing personally. Previous values were found in Samsung or the CPU vendors documentation somewhere. I'd start there or use an OHM meter on a dock we know trips desk or media mode.

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mikejr83
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Resistors are used in that location for non dock stuff too... Jigs to trigger bootloader and recovery mode, etc. I wouldn't try the rhestotat thing personally.
Thanks for the heads up! I got out my breadboard last night. Had a bit of down time at work and was just getting ready to call a few RadioShacks around town to see if they had some pots in stock (didn't expect them to, but they list a few on their website) so I could hack up a cable this weekend.

One question though, if I had the phone powered on and was to start with a linear taper pot and go from 0 to say 1M ohms (found one that would cover the entire range without me having to add resisters in there) I could possibly trip the phone into bootloader or recovery mode?

It would seem to me that in essence what I would be "doing" is plugging in various USB cables which had a different resistance in that location. It seem odd to be able to take a powered on (even screen unlocked) phone and have it just dump to recovery or bootloader with the plugging in of a cable (assuming that I had the real version of the cable/dock/jig).

That said, I'm glad you gave me a heads up as I might want to do a bit more research on this before I just sit around with my multimeter and a pot going through various resistances just to see what happens. I suppose what "happens" might be something I really, really do not want! Or, maybe I end up finding a way to unlock a VZW phone by accident! Yea, like that'd ever happen!

EDIT:
This new phone has me not writing code and doing more searching around the internets for information! I found this post http://forum.xda-developers.com/show...6&postcount=14 The poster shows that they use a 365k resistor for car dock. Preceeding posts indicate this was for a S2. I still have to go through my resistor "collection" to see what I have sitting around. I may still hack up a cable this weekend.
 
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Ok. So I got a pot and was setting up a test bed when I cut the end of a mini USB cable. I realized it only has 4 pins. My thought was to use one of the dozens of mini USB cables instead of my limited amount of micro ones for my first tests. Basically I was going to take the A side and plug it into the charger to power my breadboard.

When I saw that there were only 4 pins on the mini B side and hence four wires inside the shielding it got me thinking about the micro B end. Both the micro's and mini's A side have 4 pins. If the micro B side has 5 pins where does that 5th id pin go? Does a micro cable have 5 conductors the length of the wire which the id conductor terminates to ground at the A side?

Now I'm confused on how the accessories are manufactured so as to make the phone go from USB charge mode to A/C mode. I'd really like to sit around now that I have this pot to test various resistances in order to see the outcome. Quick Googling hasn't found any negative side effects (yet...).

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Fallon
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Micro USB has 5 pins with the new 5th pin only existing on one end to use as an ID pin for what end of the cable it is. Makes it easy for the resistors that Samsung uses to trip the various modes.

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KeithLM
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I was just looking into what all the pins do because I planned to make a small board with A and B connectors and wire the resistor in there. Now I see that's pointless. I figured the shielding on other connectors was equivalent to the 5th pin.

I'm going to have to strip down a micro USB cable and see what I find in there.

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