is it safe to add LEDs with D+ and D- line communication?
I did this schematic(attached) and the communication does not work.
where is the problem? 
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\$\begingroup\$ I would use TTL buffers in order not to disrupt the communication on the data line. \$\endgroup\$– swerCommented May 17, 2021 at 13:10
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\$\begingroup\$ @swer, the OP can't use TTL buffers. USB D+ and D- aren't compatible with TTL levels. \$\endgroup\$– TonyMCommented May 17, 2021 at 16:01
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\$\begingroup\$ You need to know the USB type you are trying to monitor. USB 1.1 devices have ±3.3-V signal levels and can operate at low- and full speeds. USB 2.0 devices have ±400-mV signal levels and can operate at low-, full-, and high speeds. Teo Comparators would probably be your best choice. \$\endgroup\$– GilCommented May 17, 2021 at 22:28
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\$\begingroup\$ It should work if you use so-called "ultrabright" LEDs, typically Green and Blue (or any phosphor color), made on 2.7-3.6V InGaN technology, with high brightness at low (0.5-1mA) current. See also electronics.stackexchange.com/q/378129/117785 Or use CMOS-3v3 logic to buffer the signals. \$\endgroup\$– Ale..chenskiCommented May 24, 2021 at 7:15
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1 Answer
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D+ (or D- for low speed) is pulled up by an 1k5 resistor. Thus the current into the LED messes up "device attached" detection.
Once enumerated, all devices get the SOF token every millisecond. That would light up both LEDs all the time, if the series resistors are much larger.
Messing with the data lines won't work with USB 2.0 high speed frequencies.
