31 Dec
2016
31 Dec
'16
1:40 p.m.
Fons Adriaensen wrote:
On Sat, Dec 31, 2016 at 07:10:16AM +0100, Clemens
Ladisch wrote:
Indeed. But if the device is _not_ bus powered, there is such a path.
Regards,
Clemens
The two data lines (D+ and D-) have controlled
impedances and drive
levels so that the effective currents are symmetrical, but when both
lines are pulled low to signal EOP, there is not necessarily an equivalent
return current over the ground line.
There must be. The net sum of the currents flowing through he cable
must be zero, unless some current takes a path (e.g. via protective
ground) not going via the cable.
If two devices are connected only by the USB cable there is no
such path.