MB V3 and 3Gs - unsupported device

[mbhiker]

So I've read through the forum posts on this topic and understand that the 3Gs is really finicky when it comes to charging/power. I've been burned by accessories that no longer work so I'm willing to give a little leeway. That said here's my problem:

I have assembled two MB V3.0 kits. One reliably charges my and my wife's iphone 3Gs and the other pops up the dreaded yellow triangle. I've triple checked my work and put the two side by side to make sure absolutely everything was in it's rightful place - it is. Reading here, I tried jumpering the middle data pins but no luck. I have not yet tried grounding the usb shield. I should note that this charges my daughter's itouch just fine, so I'm doubting it's assembled improperly.

If we assume that both are assembled correctly, and I'm using the same batteries in both (swapping them in and out for tests), and both perform consistently with 2 different 3Gs devices then I'm led to believe there is a component problem with the second MB. The only different between it and the first is that I had to get an extra resistor sent out as one was missing from the kit. As with all devices I realize that each component is engineered with certain tolerances in mind and I'm wondering if perhaps those sometimes add up to something the 3Gs just won't accept when it goes to negotiate the handshake.

Before you ask, I have not tested with a multimeter yet. I'll try to get one and post results. In the meantime, I'll take some pics of the non-performing unit so at least you can look for any assembly problems. Please help! All I really want is a working MB v3.0 for my 3Gs as we go backpacking and this is is a lightweight life saver!

[adafruit_support_bill]

The resistor divider on the USB data lines was reverse engineered from an Apple charger. It should put just under 2v on each of the data lines to emulate an authorized charger. An out-of-tolerance resistor could change that.

[mbhiker]

I bought a multimeter this afternoon and will check the data lines when I get home. I'll also upload pics at that time so you can have a look at my work and see if I made any mistakes.

[dachew]

This sounds like my problem. My MintyBoost will charge my iPod touch, but will not charge my 3gs or my wife's 4g iPhones. I've double checked, and here are my results:

No load:
D- 1.99v
D+ 1.99v
V+ 4.99v
I 2.55mA

Loaded, 4g iPhone:
D- 1.84v
D+ 1.85v
V+ 4.99v
I (screen on) 400mA
I (screen off) 150mA

Loaded, 3gs (incompatible charger message):
D- 1.84v
D+ 1.85v
V+ 4.99v
I (screen on) 400mA
I (screen off) 140mA

iPod touch:
D- 1.84v 1.74v
D+ 1.85v 1.75v
V+ 4.64v
I 1.21A

I tried all combinations of connecting D+ with D-, switching R4 (68k, 47k, 33k), nothing works. I'm totally stumped. I really want the MintyBoost for my 3gs. Is there anything I can do? Please help!

[j_jamesk]

Hi dachew & mbhiker

If you are using AA batteries try using rechargeable ones with higher mAh such as 1750mAh, I was getting random issues with charging when using AA's so I gave up on using AA's and switched to using a Lithium Ion Polymer Battery - 3.7v 2700mAh http://www.adafruit.com/products/328 and one of adafruits USB/DC Lithium Polymer battery charger 5-12V http://www.adafruit.com/products/280 boards, you connect the MB V3 to the output on the charging board and the battery to the board then you can charge the battery from either USB or DC 5v, it works 100% of the time and can charge any device that can be charged from the MB V3 via the USB output.

If you want some help with this please feel free to contact me.

[adafruit_support_bill]

@dachew - Your 4g and 3gs measurements are suspect. The D+D- voltages are derived from V+ via a resistor divider and should always be proportional to V+. I suspect that the V+ measurement for these devices is probably closer to the 4.64 you measured for the iPod touch. In any case, the output voltage is sagging and the D+D- voltage along with it. As suggested by j_jamesk, NiMH or LiPo will deliver current under load better than Alkalines.

[dachew]

Thanks. I updated the values because you are right - the iPod values were suspect. They were also typo'd and were a copy of the iPhone values. I posted the corrected values next to the originals. I am seeing sagging in the voltage, but the iPod is drawing 1,210mA (1.21A). My batteries are Sony NiMH, 2500mA variety, and I have a bunch of them which I've freshly charged. I also have a pair of LiPo batteries (850mA) that I connected in parallel after fully charging. These did not work either. It's like the phones aren't pulling a charge current at all. What's weird though, is the iPhone 4 says it's charging, but the current draw says otherwise. iPhone 3GS complains about the charger, but will draw current while the display is lit. Weird.

As an experiment, I took similar resistor values and connected them with a 5v regulated power supply (which was driven by 8 AA batteries). The resistor bridge voltage values were very close to 2.0 for both D+ and D-, and the phone charged. I also tried a configuration which yielded 2.7 and 2.0 volts, and the phone also charged.

I don't think it's a current draw problem, since my iPod touch is pulling down 1.21amps from my NiMH batteries (they get quite warm).

Does this help at all? What other info can I post?

I've also ordered a 2000mA LiPo cell that I will try in the next day or so.

[adafruit_support_bill]

It's hard to know what is going on inside the phone. But it sounds like your D+D- voltages are lower than its charger detection threshold. You might try a higher-value resistor for R1 & R3 to bump it up closer to 2v.

[dachew]

I'll give it a try and post my results back here later on this evening, along with some hi-res photos. The board is getting a little beaten up from all the soldering of different resistor combo's, and I broke the original 75k resistor so I setup a 68k + 6.8k in series (5% tolerance, and my set is about 74.1k).

Have you heard of anybody using a voltage regulator to keep the data lines at 2.0v?

[dachew]

Success! My 2000mAh LiPo arrived today, along with it's charger board. After mucking with the resistors and not getting anywhere, I finally switched to my other iPod cable. Oddly enough, it's fine! My old cable is 5-6 feet long, and I think there's too much resistance in that much copper. The cable wouldn't even work when plugged into a breakout board, which was powered by Apple charger (I was testing voltages under load from the charger). I thought that was pretty lame. But, I'm happy that my MintyBoost is working! Hopefully I'll be able to get a 1.5 charges out of my 2000mAh battery. There's opportunity (and room) in my full size Altoids container for a 6000mAh battery - that should deliver 4 solid charges. Perfect for a camping trip or a day at Maker Faire!

[adafruit_support_bill]

Nicely packaged! Cables can make a difference. I've never dissected one, but as skinny as they are the conductors must be pretty small.

[Hippeh]

This was exactly the information I have been looking for. Thanks for posting pics of your setup dachew. I'm also interested in using a 6000mAh lipo for extended use as you describe. If you've already researched the correct 6000mAh battery, would you mind posting up a link? Thanks in advance!