Carl Hutzler's Blog

I have a 6GB iPod mini and it has served me well for many years. And it continues to do the job. I have two accessories that I use all the time – a Belkin cig lighter for the car and an Airclick RF remote which allows me to hide the iPod in my wayyy insecure jeep wrangler. I just put the remote in a kinda out of sight but easy to operate location and no one realizes that there may be something worth steeling inside (well until I just posted this on my blog I guess ;-)

I also use the RF remote to control the ipod on long runs. iPod in camelbak and remote in pocket. Works well to skip over those boring tunes on a long run.

So back to the story. My 6GB mini is fine, but I have in excess of 40GB of music and manysometimes I find myself yearning for more of an artist and its just not there. So I have been looking for a way to upgrade, and recently got a 30GB video unit. But my Airclick would not work as it attaches to the top of the iPod mini and that connector was phased out after the mini. The newer Airclicks attach to the 30 pin dock connector on the bottom of the ipod and while they work with the 30GB video, they do not provide a way to charge the ipod when the remote control is connected to the ipod….there is no “pass thru” dock connector for the cig lighter to plug into (bad design Griffin).

So I began researching options for RF iPod remotes and found two that looked good. First was the iJet2 which looked fine. It had all of the controls my old Airclick had and had the pass-thru for connecting a charger when in the car. Second was the Scosche Remote which had the pass-thru connector but also offered a “shuffle songs” button which is very cool. This button allows you to go from listening to a single playlist in order to shuffling the entire iPod’s song collection. So if you are listening in shuffle mode and hear an artist you like, you can hit the shuffle button to stop shuffling songs in which case it will continue to play the songs from that artist. This is very welcome feature for me so I bought it for $50 from Targét.com last Sunday.

It arrived nearly a week later on Saturday (Target’s free shipping sux) and I hooked it up. It worked well but I noticed that the Jeep set-up with the Scosche RF remote unit plugged into the iPod and the Belkin cig lighter plugged into the pass-thru port on the Scosche was missing one small feature I liked from before. You see, the belkin cig lighter had this cool feature whereby if the iPod was playing and the power was cut to the cig lighter adapter, the iPod would automatically pause. So if I turned off the Jeep, the iPod would pause so that I could come back to that song when I returned, but more importantly, so the iPod would not just play into oblivion. But with the new set-up something was not working right.

So I queried the Internet (where else) and found something interesting on this site about Linux and the iPod Dock Connector pin-outs. Basically it said that pin#21 was used to tell the iPod what kind of accessory was attached to the dock connector. Evidently Apple uses a simple resistor sensing scheme to determine what is connected:

Pin 21 connected to ground via a resistor.
Different resistances indicate which accessory is connected.
Known resistances/functions (Ohms) are as follows:
1k - iPod docking station, iPod beeps when connected
10k - Takes my iPod into photo import mode
500k - vava uses this for his serial-via-dock experiments
Used in Dension Ice Link Plus car interface
1M - Belkin auto adaptor, iPod shuts down automatically when power disconnected

Interestingly, it even specified how the Belkin auto adapter did its magic and got the iPod to shut down. Belkin actually had very little to do with it. The iPod is evidently programmed to have an “auto shutdown when power removed” mode which is set when a 1 megaohm = 1 million ohms (1MΩ) resistor is connected from pin 21 to ground. Who would have guessed!

So I surmised that somehow the pass-thru connector was likely not passing this pin through and/or the Scosche RF adapter must have had another resistor value in its place – perhaps 500kΩ? So I pulled the little thing apart and saw that it in fact did not pass through Pin 21 and using a multimeter, found that the Scosche RF unit had only a 500kΩ to ground on that pin. So essentially the iPod new it had a serial data capable accessory attached (for the remote control communications) but it was not going into the auto power down mode. Now perhaps Scosche did this by design, but I felt like playing.

So out came the soldering torch. I disconnected Pin 21 on the dock connector completely and soldered in a huge (relative size) 1MΩ resistor. I did it crudely at first for testing and found that it worked! When power was cut, the ipod now went into pause mode. I neatened up the job and re-attached everything and now it all works the way I want.

Oh, and so far it seems to make no difference to the Scosche RF unit that the iPod now operates in auto-power down mode. I will have to use it a bit more to be sure, but all looks good.

Some pix of the final job: