[DIY] "Car Dock" Cable - USB audio out + charging - UPDATED! (11-9-11)

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I just made my own "car dock" cable based on the information over the "Fun with resistors" thread.

Basically I have a cable with a micro-usb connector that switch my phone to "car dock" mode, audio via usb/aux and charging.

CHECK THE 2ND POST FOR UPDATES, PICTURES AND A QUICK VIDEO.

WARNING:

• This cable can physically damage/destroy your phone if made incorrectly.
• If you don't have experience soldering electronics and small parts maybe you should not try this.
• The usb cable will NOT work for sync/data - just charging.
• I'm not responsible if you damage or destroy your phone/property and/or injury yourself or others.
• Use this instructions at your own risk.

Parts that I used:

• micro usb male connector (Digi-Key pn: 609-4051-ND)
  
• 619K ohm resistor (Digi-Key pn: RNF14FTD619KCT-ND)
  
• 6ft 3.5mm Stereo Plug/Plug M/M Cable (MonoPrice.com pid: 644)
  
• 1.5ft USB 2.0 A Male to Micro 5pin Male 28/28AWG Cable (MonoPrice.com pid: 5137)
  I should have used a longer cable but that's what I had at home

This is the pin-out for the usb connector:


Preparations:

1) Cut one of the aux cable connectors and expose the 3 wires:

• Yellow = common ground
• White = right channel
• Red = left channel

The left/right channel may be inverted, test on your phone before you make the cable.

2) Cut the micro usb connector from the usb cable and expose the 4 wires:

• Red = +5vcc
• Black = ground
• Green = not used
• White = not used

Soldering:

Start with the audio cable:

• Solder left channel wire to pin 2
• Solder right channel wire to pin 3
• Do NOT solder the ground wire yet

Now with the usb cable:

• Solder red wire wire to pin 1
• Do NOT solder the ground (black wire) yet

With the resistor:

• Solder 1 resistor leg to pin 4
• Solder the other resistor leg + audio ground (yellow wire) + usb ground (black wire) to pin 5

Almost done...

• Test all the connections for short-circuit with a digital multimeter
• Triple check for the right cable on the right place, you don't want to put that +5vcc on the wrong pin, it will fry your phone!
• Just finish it with some epoxy glue to make sure the cables won't break where you soldered them and some shrink tube for a polished finish.
• You must go to Settings > Dock Settings > Audio output mode and enable it to have the audio-out working.

I will post pictures next week when I will make a new cable with longer usb and better finish.
The cable I have now works fine, it's just ugly...


I hope this info will be useful for someone

Thanks to TheBeano for the info about the resistors

* * U P D A T E * *
( a . k . a . v e r s i o n 2 . 0 )

Hello all!
Thank you to all the people who rated this thread and enjoyed the info

After building my first cable from two different cables and finishing it up with some epoxy putty I started searching for a better and easier way to build this cable.

While searching on some Chinese accessories website I've found an iPhone USB/aux cable that would make this build easier and nicer.

This is the USB/aux cable from DealExtreme.com (item #34654):


From eBay I got this micro-usb connector with a "housing" (link):


The resistor is the same from the original post:


With this parts in hand I started by taking the iPhone connector apart:


With the soldering iron I removed the connector and with an blade I removed the cable "terminator"(?) so I could expose more wire and use my own "terminator"(?):


Using a multimeter and my "pro-mod" I was able to verify the cables and plugs.
All cables matched so I started soldering:


After checking for short-circuits and fixing the mistake I always make (I invert left and right channels) it was time to squeeze everything inside that tiny housing:


It looks nice but now let's test it:


Pictures are worth 1,000 words but a video is priceless (don't mind the music):

Great write up!

Sent from my SAMSUNG-SGH-I777 using xda premium

Nice write up. Very useful. Thanks

Awesome, gunna order some of these parts.

Exactly What I Wanted

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This is EXACTLY what I was looking for!! Once I see a picture/video of it in action, I'll get the parts. Question is, are you going to make your own car dock for it? Or are you going to purchase a generic dock? I'd like something that I can slide the phone into easily (and have the phone be horizontal). I am curious about the possibility of getting Digital Audio out instead of Analog. You seem to be the expert, do you think that's possible? Thanks!

I'm 95% certain digital audio out is not possible, except maybe for MHL/HDMI audio output via the MHL adapter.

There just aren't any provisions for it.

Thanks guys for the replies!

I got some PM about selling the cable. Right now I can't do it as I don't have enough time to make a good and durable cable.
The cable I have is kinda put together with epoxy putty and some shrink tubes.

Today I tested the cable and it works fine on my car.

I just found some iPod/iPhone cable that I think can make this build be easier and faster, basically you will change the apple connector for the micro-usb and add the resistor. I still waiting for the parts to arrive to test this new idea.

As Entropy512 said digital audio isn't possible with this setup but I will look in to it in the future to see if it's possible to use the mhl adaptor just for the audio.

Tomorrow I will post the pictures and a small video from it working with my current cable.

Thanks once again for the replies!

This is awesome thanks!! If you can create a few of these I would definitely be in for buying one. I am hoping to replace my itouch in the car with the phone. I already have a nice dock thus just need a cable.

Originally Posted by LGSilva

Thanks guys for the replies!

I got some PM about selling the cable. Right now I can't do it as I don't have enough time to make a good and durable cable.
The cable I have is kinda put together with epoxy putty and some shrink tubes.

Today I tested the cable and it works fine on my car.

I just found some iPod/iPhone cable that I think can make this build be easier and faster, basically you will change the apple connector for the micro-usb and add the resistor. I still waiting for the parts to arrive to test this new idea.

As Entropy512 said digital audio isn't possible with this setup but I will look in to it in the future to see if it's possible to use the mhl adaptor just for the audio.

Tomorrow I will post the pictures and a small video from it working with my current cable.

Thanks once again for the replies!

So digital audio out is not possible (that's kinda what I figured). But what about getting a USB->Digital Audio Out? I realize the kernel would have to support a device like this. I'm very new to the Android scene (less than a week). But I'd think that it would be possible. I can't post links yet, but it was a $25 USB->SPDIF device on Amazon. The reason I'm asking is that I'd like a way to eliminate the "road noise" (alternator noise) from my music.

And how are you controlling your music in your car? Do you have a remote for the phone? Bluetooth? Or are you doing it the "old fashioned way". LoL! Thanks again for your efforts!

Jim