3 ms·

Here is a demonstration with an apple-brand charger: https://www.youtube.com/watch?v=r7tf4JASzlI https://www.youtube.com/watch?v=r7tf4JASzlI A USB Power meter

by zaarn 8y ago

Here is a demonstration with an apple-brand charger: https://www.youtube.com/watch?v=r7tf4JASzlI https://www.youtube.com/watch?v=r7tf4JASzlI A USB Power meter does not inhibit the function of a charger, they only tap the power lines of the USB line with a low value resistor to measure the voltage drop. You can do it with a hall sensor too in which case you don't interrupt the voltage line at all. I see no reason why a current sensor should in any way inhibit a charger's function unless it's deliberate.

dogma1138 8y ago
It doesn’t matter if it inhibits or not but how it actually negotiated with the charger, charger only works anything that adds stuff like data or OTG requires an unlock to approve. To me this looks like working as intended.
- zaarn 8y ago
  The current sense should not add data or OTG, these devices are completely out-of-band for the USB bus. This definitely does not work as intended. Again, all this does is insert a small resistor on one side of the voltage line. It does not tap the data lines, they go straight through to the charger as normal.
  - dogma1138 8y ago
    I understand how load measurements work but it doesn’t mean it works as intended on the measurement side either. Many of those meters are not passive and provide the full USB connectivity offered by the micro controller on the output port also. So so far I haven’t seen anything conclusive, every charger I tried works but one which definitely provides OTG capability. N=1 but same goes for most of these stories so far. Could there be a problem? Sure could be cross talk on some faulty phones which makes them think there is data but it could also be that people don’t understand what is it they are connecting.
    - zaarn 8y ago
      With minimal effort I was able to find videos on youtube having this problem with apple-brand chargers too. No load meter at all or the load meter being on the live side of the charger instead of the USB isde. (Simply search "iphone xs charging problem") It seems people can make it work with a macbook pro usb c charger and other fast chargers but not with the charger that comes with the box, which IMO points to some severe QA issues. So it seems wrong to me to claim that this doesn't happen with apple-brand hardware, this should have been caught in QA, period. If the charger in the box together with this phone exhibits such a failure mode, I'd return the phone.

by zaarn 8y ago

dogma1138 8y ago

It doesn’t matter if it inhibits or not but how it actually negotiated with the charger, charger only works anything that adds stuff like data or OTG requires an unlock to approve. To me this looks like working as intended.

zaarn 8y ago
The current sense should not add data or OTG, these devices are completely out-of-band for the USB bus. This definitely does not work as intended. Again, all this does is insert a small resistor on one side of the voltage line. It does not tap the data lines, they go straight through to the charger as normal.
- dogma1138 8y ago
  I understand how load measurements work but it doesn’t mean it works as intended on the measurement side either. Many of those meters are not passive and provide the full USB connectivity offered by the micro controller on the output port also. So so far I haven’t seen anything conclusive, every charger I tried works but one which definitely provides OTG capability. N=1 but same goes for most of these stories so far. Could there be a problem? Sure could be cross talk on some faulty phones which makes them think there is data but it could also be that people don’t understand what is it they are connecting.
  - zaarn 8y ago
    With minimal effort I was able to find videos on youtube having this problem with apple-brand chargers too. No load meter at all or the load meter being on the live side of the charger instead of the USB isde. (Simply search "iphone xs charging problem") It seems people can make it work with a macbook pro usb c charger and other fast chargers but not with the charger that comes with the box, which IMO points to some severe QA issues. So it seems wrong to me to claim that this doesn't happen with apple-brand hardware, this should have been caught in QA, period. If the charger in the box together with this phone exhibits such a failure mode, I'd return the phone.