iPod Car Adapter Hacked for Carputer Use

tejesh83 · 06-21-2007, 10:55 PM

Problem Statement: How to connect a carpc to your stock audio system and use radio controls and steering wheel controls to control carpc. Specifically, I started this for my 2005 Acura TL with Navigation, but this should work for most vehicles that have a iPod car adapter that can be controlled via the headunit.

Solution: A few vendors have developed iPod adapters for my vehicle. I currently own a USA Spec PA11 HON2 iPod Adapter. It plugs into my headunit and acts like a CD changer but controls my iPod.

Instead of hooking the adaptor to an iPod, I have replaced the connection to my carpc notebook using a TTL 3.3V serial to USB adapter. Now when I hit a radio control, such as next track, the iPod adapter translates the Honda bus data to a serial command that the iPod can understand. Instead of this command going to an iPod, the TTL adapter sends the serial command to my carpc. In my carpc, I read the serial command using the program Girder and its serial plugin. Girder will translate the serial command to a keypress that I can use in Road Runner or any other event/program for that matter.

Current Status

I have successfully mapped the next and previous track buttons from the radio and steering wheel to Girder and key-presses.
There is still a quirk with the iPod detection. Normally, the iPod adapter will automatically switch the headunit whenever I turn on the hooked up iPod. I've currently hardwired this detection to pin to always on, so the headunit will always default to cd changer (now carpc) mode. Even if I hit AM/FM or CD, it will switch back to my carpc. I need to add a relay or something to make it switch only when I want it too.
My current iPod adaptor doesn't not display any text, track info, etc on the head unit. However, Dice has just released a new unit for my car that would allow this, which I could then use to send text from my carpc to the headunit such as track name, time, playlist, etc.

I'm putting this project on hold indefinitely. Initially, I thought jbors' car2pc was not compatible with my car. After doing some more research and talking with jbors, I think I will be able to use his car2pc adapter right out of the box and get a little more functionality. I've ordered one of his adapters to try out. If it doesn't work, I'll keep working on this. But for now, here's what I learned for those who may want to build their own.

tejesh83 · 06-21-2007, 10:56 PM

Heres a schematic. I figured this out the hard way, by using a digital multi meter and dissecting the iPod cable and adapter and using a pin out diagrams for the iPod dock connector.

For the 3.3V pin, I used a voltage divider (1k and 2k resistors) using the 5VCC on the USB TTL adapter header. However, as I've already mentioned, this forces my head unit into CD Changer (aka carpc) mode always. This means if I try to listen to AM/FM or CD, it will switch back to CDC (aka carpc) mode within a few seconds. So it would be better to use a 3.3V switched source possibly using a relay. I've also noticed that even if I unplug the USB adapter from the carpc, so that pin 6 on the 8 mini din connector gets no 3.3V, the iPod adapter will still automatically switch to CDC/carpc mode. My guess is that for this adapter, simply grounding or grounding through a resistor is enough to trigger the pin, but I have not verified this. It may even be possible to ignore this pin altogether. I have not experimented yet, since I've already ordered jbors car2pc adapter. If it doesn't work, I may look into this some more.

Now, to get the serial communication working on your carpc, just install the drivers for the USB TTL adapter. The drivers register the adaptor as a standard com port. Here's what I did in Girder. You should use 19200 8N1 as the com port settings.

I set the Girder serial plugin to detect variable length messages with a 100ms timeout. I set the terminator to "aa", since that should not appear in the packet. After 100ms, the plugin will just return the full HEX string.

Now you can just configure Girder as normally would with any other remote or device. Just use the "Learn Event" button. Add a command to Girder. Click the Learn Event Button. Press the radio or steering wheel control you want to train. Girder will record the packet string, and thats it. Now just set the keyboard map or whatever else you want to do this with event. The best part is you don't have to know anything about the iPod serial protocol. Just enjoy

However, if you plan to use the advanced remote features, for example to send text/track/playtime to the Head Unit, you will need to learn to decode/encode the protocol. I've attached a link to a wiki where you can learn more about that.

Parts List:

An OEM iPod Car Adapter.
- Usually connects to the bus, CDC, or SAT connector on the HU. I recommend that you choose one that supports the simple remote protocol. You can tell by if you can still use the iPod click wheel and radio controls at the same time. The usa spec adaptor I'm using has a little toggle switch I can use to set the mode. The honda music link does not.
USB TTL 3.3V Serial Adapter
Optional parts
- A few resistors for the voltage divider I'm using to convert 5V to 3.3V
- Possibly a relay for the 3.3V pin
- An 8 pin din cable or connector for easier hacking.
I used non-stranded copper wires from an old ethernet cord for testing. Fits perfectly in the mini-din pin holes.

Mainly you just need something to decode the Serial TTL 3.3V signals. I recommend the one I've posted, as its pretty simple to use and only $20. However, you could also hack up most cell phone data cables (like those at radio shack) to do the same thing. They typically work on the same principle (3.3V TTL to USB Com port adapter), and may even use the same chip inside the cord.

Useful references:
iPod Pinouts
iPod Accessory Protocols
Acura Music Link Pinouts
Acura Music Link hacking

trashkk · 06-22-2007, 12:55 AM

Thanks for the Ipod interface information. It was good information especially with the how to capture serial data explaination.

I have a 2004 TL with no navi and I am the first in Acurazine.com to installed a factory navi onto a no navi but now I am thinking of puting a carputer into the sytem becasue the factory navi and the stereo system is only limited to CD and DVD-A. I have the car2pc interface with me now but haven't got a chance trying it out yet. I might able to hook it up sometime in July. Please let me if you have got your 05 TL working with the car2pc interface.

Update:
Carputer project started today. 07/17/2007
- rewire factory navi LCD screen to a usb touch controller. (it has been done by others in this forum)
- tested the usb touch to pc and confirmed working

lifter · 09-14-2007, 08:43 PM

Great info! Thanks for posting all this. I'm going to apply for this thing:
http://www.scosche.com/scosche_ipod....&ItemID=IPNRFC

rajpr00 · 11-25-2007, 11:09 PM

I was thinking about doing something like this for the longest time but until I found this thread I didn't realize how easy it would be. I managed to get this working with the Audiolink Ipod adapter on my Mazda6.

The pinout was slightly different but a 5V TTL-USB worked great. Had to mess with the Girder settings for awhile before I got something to work consistently. I haven't quite gotten it 100% perfect since I can't hit my steering wheel controls in rapidly or leave them held down to scroll quickly but it's good enough for now.

hope1984 · 12-05-2007, 12:02 AM

Hi there all, i'm currently trying to interface my clarion vrx950 with my carputer, i'm using the clarion ipod adapter which i have modified, i can get communications from the clarion hu to girder but when first turned on headunit says "loading" and girder reads FE66E60000066080FE66E600600018EOF from hu after about 10secs hu times out and comes up with error, i'm using all the settings you have suggested but still know luck does the hu need some type of data string back to confirm that it is connected? I'm only knew to this so any help greatly appreciated..

rajpr00 · 12-09-2007, 08:44 PM

Your adapter might be trying to use the "Advanced" Apple protocol where it sends commands to the ipod and expects responses. You can get some details from the Apple protocol page that is linked further up. If that's the case then you'll have to write some code to work correctly since the method above is setup for the simple remote protocol.

alarmed · 12-23-2007, 11:23 AM

Hi been try to get this to work for the past couple of day and really struggerling.
I just can't get it to communicate or see any data!!!!

I know it will be down to me so go easy :-)

I bought the usb-ttl 5v cable from fdti (thought i ordered 3.3v version but 5V turned up) would this cause any problems?

I have a Dension Gateway 100 ipod interface which i have hacked the cable to workout pin configuration Can supply if it helps

I could not find the same version of Girder as above so this is my first problem as what to set and where to find it ( found version 3.3.4 and ver4 & 5)

Is there a way I can check the usb-ttl cable to make sure I have'nt damaged it

Thanks Paul

alarmed · 12-27-2007, 12:36 PM

Anyone got the pinouts for a dension gateway 100?

Think I've made an error dissecting my ipod cable

hope1984 · 02-09-2008, 12:58 PM

yeah i dont know if the 5v will work since the ipod uses 3.3v make sure that you connect the 3.3v pin on the ipod (pin 13) and ground to the ttl/usb circuit or you will not get any data showing up. you can drop the voltage down with a suitable resistor. pin diagrams for ipod http://ipodlinux.org/Dock_Connector
I dont know about the gateway product though hope this helps a little.