USB Hub as an iPod/iPhone Charger (iPod Powersquid)
*** Be WARNED. If you try this and fry your iPod/iPhone, don’t come crying to me! **
** Do this at your own risk **
My family has an ever growing iPod/iPhone collection. It is actually sad in a way, but it is what it is. We currently have three iPhones – First gen, 3G and 3GS. And we have a first gen iPod Touch.
When we go on vacation or a trip to visit my parents, we bring along a charger but the issue is that with four devices, someone is always needing a charge at the same time as someone else.
So I started playing around with USB hubs. Given that a simple 4 port USB hub that has an external power supply can supply 500mA to each USB port, I figured I could easily charge four devices. Not so as I would quickly find out. Most iPods and iPhones will not simply charge when they are connected to a USB port UNLESS that USB port is directly or indirectly connected to a computer.
From what now seems like endless experimentation, I have found a solution. To trick the iPhone/iPod into thinking it is connected to something it can charge from, you simply short the USB Data+ and Data- pins together. So basically if you provide 5V and GND on pins 1 and 4 and short the middle two pins, many iPods/iPhones will charge. I have tested the following:
iPhone 3GS – charges
iPhone 3G – charges
iPhone First Gen – charges
iPod 30G 5th Gen – charges
iPod Nano 3rd gen (the sort of square one and the first with video) – DOES NOT CHARGE
iPod Shuffle (2nd gen square shape with buttons) – DOES NOT CHARGE
So if you have a newer iPod or iPhone, chances are that my method will work for you. And if you have an old hub (USB 1.1 is just fine) that allows for external power (and you have the power adapter), you might give this a whirl… (click any image to enlarge)
1) Open up the hub.
2) Find the circuit traces for the middle two pins on the USB ports (Data+ and Data-). Using a dremel, screwdriver or whatever, cut through the traces so that these pins are isolated from the USB hub circuitry. ( Note: the USB hub will never work as a hub again)
3) Solder the middle two USB pins together (Data+ and Data-) so they are just shorted (no voltage on them)
Re-assemble the hub and test with your favorite iPhone/iPod.
I think the reason this works is that the USB charging spec has a way for a USB port to tell a device that it can charge or that it is a charger. While there are several ways to do this and the chip inside the device seems to have some sort of role as well, one of the ways is simply shorting the Data- and Data+ together. I discovered this by accident but later have confirmed on some forums that this may be the reason this works. And perhaps earlier iPods did not sense this while later units did.
One other note… it seems that to charge the last gen iPod Nano (first with video) and the iPod shuffle (2nd gen square shape with buttons) and everything else in the iPod/iPhone line you need to put USB Data+ and Data- at some voltage….many people on the forums claim 2.5V for each or 2.0V for one and 2.8V for the other, etc will work. And from my testing that seems to be the case. So if you want to really have a universal charger for every iPod and iPhone, you would have to go to the trouble to solder in a simple voltage divider into the USB hub. A pair of 330Kohm resistors, in series between 5V and GND would do it. Then solder the junction where the resistors meet (2.5V) to USB Data+ and Data-. That would do it. And I may do this someday, but for now, since the newer iPod/iPhone units seem to like a simply short, and since I am lazy, well, that is the way I will leave it.
And a final note…in my testing I found that the iPhone 3GS drained about 600mA while it was doing a “lot of work” like charging a fairly dead battery (20% life left), streaming a 64kbps radio stream over 3G and with the brightness full up. So while the hub will provide 500mA, it may not be enough to keep the device going non-stop under these conditions. For a solution to that issue, you would have to design your own power supply or buy one I guess. a 1A supply should be enough and that is what Apple’s own power supply is rated for….although I never saw it providing that much in my testing.
Addition: I can now say that a simple voltage divider which gives about 2.5V on the Data+ and Data- pins will get the iPod Nano to charge (the suqareish nano and first that supported video). But strangely, the iPod shuffle 2nd gen will still not charge. Hmmm.
*** Be WARNED. If you try this and fry your iPod/iPhone, don’t come crying to me! **
** Do this at your own risk **
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Would it be possible to create a “cable” to plug into the hub’s upstream port that will provide the same results and not permanently disable the hub function? I have a powered hub that I use similarly to you but do not want to permanently disable it.
Great question. I thought about the same thing. But I do not think it is possible without some further know how. The iPod/iPhone wants to “talk” to a real computer over the USB port. This involves sending and receiving data on the USB Data+ and Data- pins. The likely protocol communications include what type of device is at either end…things like power management, speed of each device, etc are negotiated. I assume the iPod figures out it is connected to a real computer during this negotiation and at some point allows charging.
What I am doing in my charging hacks is using a non-computer charging option. The iPhone can obviously charge from a simple power supply. 5V DC. But for some reason Apple’s engineers do not allow it to simply charge when it senses 5V DC (like many other phones, blackberry device, etc, do allow). And there may be a good reason for this, but I know that is not your question.
So basically what I found from googling around is that the iPhone’s charger (the one that comes in the box with the phone) has certain voltages on the USB Data+ and Data- pins. And if you simulate these voltages (about 2.5V on each), the iPhone will happily charge. Yet another option is to simply short the USB Data+ and Data- together….not to any voltage…just together. The 2.5V seems to work better for charging a larger variety of ipods/iphones. But simply shorting the Data+ and Data- will charge all the iPhone models I tested (first gen, 3G and 3GS).
So in answer to your original question, there is not much you can do on the USB upstream port to solve the charging issue other than faking the actual USB protocol used by a computer. Maybe someone knows how to do that, but my guess is that would be challenging to say the least. And keep in mind that the upstream port data+ and data- pins are connected to internal circuitry in the USB hub. So you can’t just short those two pins (or put 2.5V on them) as that will not do what you want (and may blow the hub entirely – who knows).
Have you thought about freecycle.org and finding someone with an old USB 1.1 hub you can trash for this purpose? That is what I did. Or you can sometimes find USB hubs for next to nothing online or even a local box store. Just make sure it comes with a wall adapter….that’s where the juice comes from!
Thanks, after I posted the question I realized that it wouldn’t work because the short would only be on the upstream port. It doesn’t travel through the circuitry. Now my thoughts are towards an “adapter” that could be plugged into the hub and the iPod into that. The adapter would just have the shorted connections. I guess if I wanted to get real fancy the “adapter” could also be wired to provide that 2.5v to the data connections…
But you will have the same issues. The downstream ports (four of them in a four port hub) are not simply tied to each other. They are tied to circuitry in the hub. So if you create some sort of external USB “plug in thing” that has the middle two pins (data- and data+) shorted, you will short out the USB hub circuitry when you plug it in. Or if you tie these pins to 2.5VDC, you might do even worse things to the hub. And since the USB ports are NOT tied together, the shorted USB plug you create will not provide a short to the other USB ports either (which is what you were hoping for).
What I did with my hub is to use a dremel and a knife to scratch away the circuit board traces for Data+ and Data- each USB port (four ports, eight traces in all). This isolated the middle two pins on each of the 4 USB ports on my 4 port hub. I left the outer two pins (V+ 5VDC and Ground) intact as they ARE simply all connected to each other and to the 5VDC external power supply.
Then I soldered each of the USB ports’ Data+ and Data- pins together (center two pins on EACH port). In addition, you can create a simple voltage divider inside the USB hub using two identical resistors (something in the 100K Ohm range to limit current drain). By connecting the resistors together in series and connecting the other end of one resistor to 5VDC and the other end of the other resistor to ground, you will get half of 5VDC in the middle where the two resistors are connected to each other. Connect this 2.5VDC to your shorted Data+ and Data- pins for EACH USB port and you will have the 2.5V that seems to make even non-iPhones charge.
But keep in mind that to do this you MUST (should?) disconnect these Data- and Data+ pins from the other USB circuitry. Otherwise you will be sending 2.5V to this circuitry and who knows what it might blow up/short.
Yes, I probably would have fried the first one before I realized I had not isolated the center pins in the adapter from the hub. I think what I have in mind would work the same as your solution as I’m only trying to off-board the changes. Off-boarding leaves the hub in a workable status and still able to create a short for a particular port. And the added benefit of not requiring changes to the whole hub. It would however be much less elegant to look at and require additional items to work. For a mobile setup my idea would be a major pain, but for a stationary setup, which is what I have, it would be less inconvenient than a second hub. Maybe. ;)
A 2.5v powered solution would not likely be an easy thing to put in a small adapter forcing a larger size. Even less elegance/more hassle.
I did this with a Belkin 4 port USB 2.0 hub I bought at Best Buy. Needed to charge 4 iPods at same time. I have iPod Touch 2g’s. Worked like a charm.
One thing, I was having some trouble making it work, Then I discovered a trace on the back of the board that went to a surface mount capacitor. I had to cut the 2 traces going to the middle pins, plus each jack had this extra trace that needed cut on the other side of the board.
I also discovered that when you short the middle pins and the iPod beeps and begins charging, you can then remove the short from the middle pins and the ipod continues to charge.
My USB hub came with a 2.5A rated wall adapter.