Support and General Use > Hardware
Investigating the iPod USB charging bug
NiHaoMike:
--- Quote from: gevaerts on March 27, 2010, 11:10:20 AM ---It can't. It can detect the difference between a port with an active host and a port without. The lack of an active host does not imply a charger.
--- End quote ---
How does it detect that? From what I know, the iPod will not reboot into disk mode if the data lines are left floating.
I think that problem would mean that accessory devices that supply 5v power (and do not use USB mass storage mode) would be limited in functionality. Could be a pretty big problem for some users.
torne:
It detects that because active hosts enumerate the iPod and set up a USB connection. It's not detected by voltages.
NiHaoMike:
--- Quote from: torne on March 27, 2010, 10:14:36 PM ---It detects that because active hosts enumerate the iPod and set up a USB connection. It's not detected by voltages.
--- End quote ---
Thanks. I was under the impression it sensed impedances or something.
Is it possible to sense impedance to ground? USB is terminated on the host side with a pair of 15k resistors to ground. So if it's possible to tell the difference between 15k and open circuit, it's possible to tell the difference between USB and a power supply.
torne:
That doesn't tell you the right thing either. You are assuming that anything which doesn't connect the data lines is a power supply. This is not acceptable as a default.
I'm pretty sure it will work fine for your purposes once the charging rework is done.
NiHaoMike:
--- Quote from: torne on March 28, 2010, 05:14:01 PM ---That doesn't tell you the right thing either. You are assuming that anything which doesn't connect the data lines is a power supply. This is not acceptable as a default.
I'm pretty sure it will work fine for your purposes once the charging rework is done.
--- End quote ---
What else would connect 5v power but leave the data lines floating? That device obviously isn't going to communicate, so the only logical reason for it to supply 5v is for power. (If you're thinking of the case where a wire is broken, I wouldn't bother since all bets are off if the cable is bad. A cable can also short 5v to ground, and there's nothing that can be done on the device side to handle that.)
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version