WhistlinDixie

The iPod Project: Part 2

Ok, so it’s been a while since I started this project. Let’s just say that my last quarter as an undergrad was a ton of work and the thesis that I churned out in a week took a month to push through to final approval. So, here I am, ready to continue the project.

I actually did this a month and a half ago, but haven’t had the time to write about it. I tried what I outlined in the first post, and, sadly, it didn’t work as planned.

The particular FireWire cable that I purchased didn’t appear to be up-to-spec since it did not have shielded twisted pairs, instead having only a single braided shield for the whole cable. In an attempt to increase the fidelity of the audio being delivered to my car stereo, I used some old stereo cable, which has each channel individually shielded, to carry the audio and the FireWire cable just to carry power to the iPod.

After I assembled all of the parts, I installed the cable in my car to test it. The audio worked great. After plugging in the adapter, I was able to hear my music out of the speakers in my car, without any noticeable distortion. I noticed rather quickly that the charging icon was not appearing on the display. To make sure that it should show up, I pulled out my USB charger and plugged it into my iPod while it was playing music. Sure enough, the charging icon showed up.

I am not sure why the iPod refuses to charge when given approximately 12V to its FireWire charging pins. I can only figure that Apple got rid of the circuitry for charging at FireWire voltages. Since I do not have an official FireWire adapter, I cannot test this theory.

So, I will attempt an M2 of the project the next time I am home, around Christmas. In this revision, I will use a USB car adapter to provide power and hook it up to the USB charging pins in the dock connector. I am hoping that I can find a place to tap into the cigarette lighter circuit in the car so that I’m not required to have the adapter plugged into the cigarette lighter at all times.

Gallery of iPod Doc Connector M1

The iPod Project: Introduction

I recently purchased a 5th gen 60GB iPod from Jim at coast trash. I threw Rockbox on it so that I could play my FLAC-encoded music, and to get rid of as much of the Apple as I could. (I even set up a VM just for iTunes to keep Apple crapware off of my computer.) All has been great so far, even though I have only used the iPod around my apartment.

I have this tendency to take long road trips, such as a back-and-forth between central Ohio and Jackson, Mississippi. I am too lazy (perhaps too focused on the road) to bother trying to tune in radio stations as I pass through cities, so I just listen to my music. Luckily, my 1998 Honda Accord has a 6-disc CD changer in the trunk. This is normally good enough to get me from meal to meal. However, I need to strategically pack my trunk so that the changer doesn’t get buried underneath piles of my junk. Also, I don’t carry much of my music library in CD format in my car, meaning that there is a decent bit of it that I can’t listen to in my car.

On a recent drive to my friend’s apartment, which is about an hour from campus, I decided to dig out the cassette tape adapter that I got around the same time I got my old RioVolt PSX100 and try it with my iPod. It worked nicely, but used the headphone jack, which meant that my music went through two EQs, leading to highly exaggerated bass and treble and non-existent mids. Since the settings to disable the EQ in Rockbox are buried about three levels deep in the menus, I had to stop right off the bat to fix this problem.

This gave me an idea: integrate my iPod right in to my Accord. I want to get to the point where all I have to do is plug my iPod into a dock connector and get audio and charging all at the same time, since my drives tend to be about 13 hours, longer than I expect the battery on the iPod will last.

I have done some digging to find some details on what I’ll have to do. First, I would need to build my own dock connector. Second, I will need a way to get audio into the factory-supplied Honda head unit. Lastly, I need a way to get power from my car into my iPod.

My plan is as follows: order all of the parts, assemble the dock connector, then wait until I can go back home, which should be Labor Day weekend. At home I have the tools to disassemble my car’s dash board so that I can get to the back of the head unit. I will need to find a way to mount the Honda-to-RCA adapter since it is large enough that I don’t want it dangling. I will also need to tap into the power lines for the cigarette lighter to get my power. I want this to be as unobtrusive and unnoticible as possible, so I don’t want to occupy the cigarette lighter with an adapter. I will also need to decide where I want the dock connector to be (armrest, cup holder, dash, etc.).

I plan on using a Firewire cable as my cable harness. Firewire provides a +V cable and a ground cable capable of handling the currents required to charge the iPod over Firewire. It also provides two shielded twisted pairs of cable, which I will use for carrying the audio signal to the head unit. The shielding should help keep out any noise generated by the car. I have not decided whether to run the channels of the audio signal through the same twisted pair, or each through their own twisted pair.

Using the pinout chart from Pinouts.ru, I have an initial pinout that I will use for the dock connector:

This should be a fun project. I will do my best to keep you updated on my progress and provide pictures of what I’m doing. If all goes as planned, this should be done before I go back to school after Labor Day weekend. If not, I should still have it done before my next drive down to Mississippi in October. I guess the radio and my CDs will have to do until then.

EDIT: I forgot to include the accessory indicator resistor in the pin out chart.