Can't charge the iPhone 3GS with voltage signaling from Mint

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Cuby
 
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Can't charge the iPhone 3GS with voltage signaling from Mint

Post by Cuby »

Hello all,

I am not a customer yet, as I wanted to read at lengths about charging the i-Devices. Then I read the remark on charging the most finicky one, the iPhone 3GS. Unfortunately I have two of these. While the iPad is happy charging on different signaling voltages, the iPhone would charge once in 10 times, approximately, otherwise would trick-charge at 80mA, frustrating in itself as there's no consistency. At first, I suspected the 5V voltage wasn't stable or too low, as happens on countless USB chargers, so I used an old, highly regulated switching power supply and set it at 5.1V.

I tried combinations: 51.1KΩ, 75KΩ, 43.2KΩ, and 49.9KΩ, 75KΩ, 43.2KΩ, and the 75KΩ / 49.9KΩ dual divider, the 68KΩ / 47KΩ (single pair) voltage divider, and another one I found there. None would charge the 3GS reliably.

I also happen to have a Blackberry 5V 750mA charger that has no problem charging the dreaded 3GS or the iPad, and a 12V inverter that has a USB port, also able to charge the 3GS, even though it has rather bad filtering (low-voltage line goes directly below high voltage transformer). A dual-USB charger from RCA, a round model, also has no issue charging the 3GS.

I checked the inverter first, and it appears the manufacturer was able to score non-standard resistors. Reading the color code on them, they are exactly 51KΩ, 47KΩ and 75KΩ, all 1%.

But trying to reproduce the schematic using 5% resistors on a breadboard failed to charge the 3GS, even though measured resistances were exactly the required ones. I guess that's pretty much a dead-end here trying to score non-standard resistors.

So has anyone tried to reproduce the Blackberry charger instead? I am not sure how to open it. Could there be another protection mechanism preventing the 3GS from reliably charging?

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ThomasDr
 
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Re: Can't charge the iPhone 3GS with voltage signaling from

Post by ThomasDr »

Hello,

I do not know if I understand your problem correctly.
But apple needs a voltage on the data lines, so that the load device unlock.
There is a lot schematic for it on the net. E.g. here:
http://www.fabimon.org/2012/08/27/iphon ... ber-bauen/
http://www.instructables.com/id/How-to- ... homemade-/
https://www.google.de/search?q=ipod+usb ... CAYQ_AUoAQ

regards
Thomas

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Cuby
 
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Re: Can't charge the iPhone 3GS with voltage signaling from

Post by Cuby »

That's what I did. No combination to get the required signalling voltage seems to work, including the one stated on Adafruit.

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ThomasDr
 
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Re: Can't charge the iPhone 3GS with voltage signaling from

Post by ThomasDr »

Hello,

ok, i use one with all the same resistors.

regards
Thomas

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Cuby
 
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Re: Can't charge the iPhone 3GS with voltage signaling from

Post by Cuby »

What values are they?

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adafruit_support_bill
 
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Re: Can't charge the iPhone 3GS with voltage signaling from

Post by adafruit_support_bill »


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Cuby
 
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Re: Can't charge the iPhone 3GS with voltage signaling from

Post by Cuby »

Exactly as I tried. The 3.0 version resistors do NOT work with the 3GS.

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adafruit_support_bill
 
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Re: Can't charge the iPhone 3GS with voltage signaling from

Post by adafruit_support_bill »

The 3GS is notoriously finicky. Apple, at the time, was still trying to discourage third-party chargers. As noted in the compatibility guide, the 3.0 Mintyboost 'works with most' 3GS phones. We can't guarantee that it will work with all.
https://learn.adafruit.com/minty-boost/compat-v3

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Cuby
 
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Re: Can't charge the iPhone 3GS with voltage signaling from

Post by Cuby »

No of course, I read that, but as I reverse-engineered an inverter where the voltage divider was extremely similar, I found that one worked, but used non-standard values resistors.

On the other hand, I heard about manufacturer Pericom, who makes SOT-23 packaged chips they claim is able to emulate whatever combination used to "tell" devices about charging capabilities.

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