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July 16, 2008
iPhone 3G Firewire Charging Adapter
Update: CableJive will be selling an iPhone 3G Charge Converter starting around the end of August or early September.
Lots of folks are looking for something to fix the fact that their 3G iPhone doesn't work with existing iPod/iPhone docking devices. Apple didn't tell folks prior to the iPhone 3G release (including those in the "Made for iPod" program, my sources say) that they were disabling the ability for the iPhone to be charged using the 12V Firewire (on pins 19 & 20 of the Apple connector). Many accessories rely on this for powering the iPod/iPhone. To be fair, Apple has been pushing USB for some time, with some warnings to inside folks.
As an Apple activist and iPod/iPhone accessory hobbyist I've gotten a dozen or so emails about this problem. Folks want a solution that will let them plug their 3G iPhone into a device that provides Firewire power and have it work.
Conceptually, this isn't too difficult. I've made something for the Bose SoundDock, which took the 12V from the Firewire, reduced it to 3.3V to provide power back to the device to trick it into thinking an iPod was connected.
The iPhone 3G Firewire Charging Adapter is a slight derivation from this. The idea is to take the 12V from the Firewire pins (19 & 20), use a set of resistors to reduce the voltage to 5V, and provide that on pin 23 (ensuring ground is also sent to pin 16). Thus the female side of the adapter gets 12V on the Firewire pins, but the male end of the adapter outputs 5V on the USB pins.
Having made custom iPod/iPhone cables in the past I'm familiar with the amount of labor that goes into making this kind of thing from raw parts. For all the folks who expressed interest in the dock extender I hacked up, I (and a small team) made them for anyone willing to pony up $65 to cover the parts and the labor (a price that shocked some, but was no sweat for others).
I really don't have the time, but I can't resist throwing this idea out there to see what other folks are thinking.
Update: CableJive will be selling an iPhone 3G Charge Converter starting around the end of August or early September.
Posted by mike at July 16, 2008 7:57 AM
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Comments
This is the same idea I had, although I was thinking of using resistors to bring the voltage down to 7V, and then a regulator to bring it to 5V. I was hesitant to use only resistors, because, for example, car supplies often vary between 12V and 13.6V. Dropping it 7V via resistors would give you 6.6V on 13.6V, which is far out of the 5.25V max of the USB spec.
The other concern I have is whether or not there needs to be something on the "accessory indicator" pin or the USB data pins to say that "hey, I support USB charging!" Have you tried building the adapter you propose? I'm interested to hear if it is indeed that simple.
Posted by: Craig Kovatch at July 16, 2008 2:49 PM
I'd definately be interested in the adapater or at least in knowing exactly how it works. I am actually currently in the process of attempting to modify my Belkin Auto Kit to be iPhone 3G compatible. I ran into the 'charging not supported over FW' message and ended up here. Optimally, I would like it to:
- Charge via USB
- Working Line out
- No 'This accessory is not supported...' pop up
- Phone calls over car speakers
I was thinking of something very similar to your post to get charging working. I would just reduce the 12V to 5V and switch the power to pin 23 (USB power). Although, I am leary to approach this without some further research on how exactly the best way to go about this is.
Line out should be easy enough to handle. It may actually already be working. (I haven't had a chance to test that part yet)
I'm still stuck on what to do on getting rid of the annoying "This accessory is not..." pop up. It doesn't actually pop up any more on the iPhone 3G because I get the "charging not supported over FW" message instead. I imagine if I got USB charging working, I'd see the message again. I read that it has something to do with the resistance it detects on pin 21 (Accessory Indicator). 1KOhm seems to detect as a "iPod docking station" and "beeps when connected" according to pinouts.ru, but I am not sure how to further approach this.
Phone calls over car speakers is a low priority, but it would be nice. I don't even know where to begin on this one. It's obviously possible to get phone calls over line out via headphones but not sure how to get it out of line out on 3/4. Maybe it has to detect that a microphone is present, since the Apple headphones have that integrated.
I also read your previous iPhone post regarding the undocumented pin 7. That also may be an issue I later encounter. Not sure.
Your thoughts?
My email is austinrobertson [AT] yahoo [DOT] com.
Posted by: Austin at July 16, 2008 3:02 PM
Also, one other concern: if we drop the 12V to 5V for USB charging, which ground do we use? Can we still use the firewire ground? Would it need corresponding resistors? (I'm not familiar enough with electrical theory to understand what a "ground" really is...)
Posted by: Craig Kovatch at July 16, 2008 3:41 PM
I'd be interested in purchasing one!
Keep me posted.
Posted by: Joshua at July 19, 2008 3:39 PM
I would love an adapter to make my 3g iPhone charge in the Bose Sounddock, I'm not about to open stuff up so how much for me to get a custom piece from you? :)
Posted by: Denise at July 20, 2008 9:12 PM
I'd love to buy this adapter if you guys get it working! Pls contact me!
Posted by: jason at July 21, 2008 12:29 AM
I would love one...My cars Ipod adapter no longer charges my iphone (now 3g), but still plays music etc...please let me know
Posted by: Wayne Friedman at July 21, 2008 2:32 AM
I would pay for such a device.
Posted by: Justin at July 21, 2008 6:24 PM
I'd buy one today seeing that the new 3g is on its way to me. I could keep my old iphone and not have to deal with this problem but I just bought it (after may 27th) and will get $150 bucks back by returning it and buying the new one.
Posted by: Nicholas Topping at July 21, 2008 7:10 PM
Can't charge my new iPhone 3G in the car (using an ipod2car). Would this adapter work? Is it Female 30-pin to Male 30-pin??
Posted by: Brian at July 23, 2008 10:17 PM
I'd be keen to get on of these if you guys are planning on making some
Posted by: Steve Ruston at July 25, 2008 11:02 AM
I'd also be interested in buying or getting plans for one of these, as my AuxPod (same thing as the Neo Ion or the iPod2Car) doesn't charge in the car, but audio functions just fine.
Posted by: Adam at July 26, 2008 12:31 AM
I would happily pay for this type of adapter to connect my iPhone3G to my cars iPod connector and get power (it works fine with everything else except charging). If it was built to last $65 sounds fine.
Posted by: Casetin at July 26, 2008 12:24 PM
I would pay for this kind of adapter. Hope you get enough interest to start producing them.
Posted by: fb at July 27, 2008 10:42 PM
I'm making one for testing purposes right now from an iPod extender/breakout board and a linear 5V regulator chip.
There's a few design issues here, though:
* You have to use the unregulated firewire line to produce a 5V source that's inside the USB power specifications. There's no way you can do this with resistors, as the input voltage could range from (say) 9-10V to over 25V (depending on the source of the Firewire voltage), and the load can vary widely too (depending on what the iPhone is doing).
* If the iPhone decides to draw the full 500mA that it could draw from the USB power, then you're going to be dissipating almost 5W from a linear regulator (14.4 - 5)*0.5 , so a switching regulator is probably in order here. And that's with an automobile supply; higher Firewire voltages would be worse.
* You have to be able to do the right thing if your adapter happens to be plugged into any iPod dock connector, regardless of whether USB, Firewire, or both power supplies are present.
Further, Apple is working on one of these adapters (according to third-hand information).
Posted by: Ned Konz at July 28, 2008 1:45 AM
Ned, where'd you hear that Apple is making one? I'd be happy to wait if they are indeed going to put one out. Can't be any more expensive than Ridax's pre-order offering.
Posted by: Craig Kovatch at August 4, 2008 5:21 PM
I've experienced same problems on my Mathey's car charger (for iPod 5G with audio out).
First time I put it on the charger, iPhone 3G displayed well-known allert, that said you can't use this accesory.
So I decided to modify this charger to adopt iPhone 3G.
I fond that this adaptor supplys power from car adaptor (12v) into FW pin directly (pin # 19). But I could still charge 5G with this.
That means, recent iPod uses USB charge but still it remain FW charge ability, maybe because of convenience to develop car charger for 3rd venders.
But, iPhone 3G doesn't. So I decided to make small DC-DC converter using regulator (maybe 78xx series). But soon after I opend up charger, I fond power supply units on the board, maybe for FM transmitter. It uses UTC78D05A, it supplys 5V 1A and is enough for iPhone 3G. So I cut FW supply cable into Dock connector and branched the output terminal of regulator on board into USB charge pin of Dock connector (pin # 23).
I tested with my iPod 5G and it still works well.
(still charging by USB pin with 5V !)
But, sitll can' t for iPhone 3G.
As mentioned above, this has to do with resistor between #21 (accesory sense pin) and #30 (GND).
Matheys charge stand has 2M ohms between 21 and 30.
But Belkin, 1M ohms. Maybe there's a secret on the number
of resistance.
I really would like to know how much resistance I should connect between 21-30. I could not find any helpful information on the webs so far.
Some people said it also neccesary to pull-up and pull-down of USB positive/negative pin with certain resistances.
Posted by: Spiky at August 14, 2008 4:45 AM
Quoting Spiky "I really would like to know how much resistance I should connect between 21-30. I could not find any helpful information on the webs so far."
Anyone determined the resistance required here? I have a Mazda factory fitted iPod car adapter and would both like to regulate the FW 12v to 5v to allow my iPhone 3g to charge while also re-enabling the ipod screen as it's impossible to navigate through a lot of track using the controls on the head unit. I assume this is possible because my Logitech mm50 allows control and iPod interface to remain visible and enabled.
Posted by: Richard Guest at September 10, 2008 2:37 PM
From pinouts.ru
(Pin 25 & 27 are the USB DATA pins)
"Pins 25 and 27 may be used in different manner. To force the iPod 5G to charge in any case, when "USB Power 5 VDC" (pin 23) is fed, 25 must be connected to 5V through a 10kOhm resistor, and 27 must be connected to the Ground (for example: pin 1) with a 10kOhm resistor.
To charge an iPhone 3G, usb data- (25) should be at 2v, usb data+(27) should be at 2.8v. This can be done with a few simple resistors: 33k to +5v (23) and 22k to gnd(16) to obtain 2v and 33k to +5v and 47k to gnd to obtain 2.8v. This is a "notification" to the iphone that it is connected to the external charger and may drain amps from the usb."
So for a 3G phone...
+5V (pin 23)
|
33k
|
pin 25 (2 volts)
|
22k
|
gnd (16)
+5V (pin 23)
|
33k
|
pin 27 (2.8 volts)
|
47k
|
gnd (16)
(I am not responsible for any mistakes or what happens to your equipment)
Posted by: Kevin at November 26, 2008 1:19 PM