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USB

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amel:
Hello,

I found a problem with this schematic, there is no USB communicatio. what is the problem with this?
thank you.

Renate:
The Vcc of the two sockets is not connected.
You can't drive LEDs off the data lines.

amel:
Thank you for your response, but I know that when we use USB as a device it is not important to connect VCC (connecting just D+,D- and GND): you can correct that for me if it is'nt true.
can you explain for me how i can't drive LEDs off the data lines.

bateau020:
Can you show where those labeled lines are going to? That might help.

Do you connect leds between the resistors that are shown and ground?

In that case, see 3 potential issues:
1) USB requires the data line to be pulled high in the nominal case. You will need the VCC to pull high.
2) the USB data lines are high speed lines. They are sensitive to the load on them. Better to use a driver to drive the leds. You will need the VCC for that.
3) leds act as photocells when you shine light on them. That light may also disturb the signal. Again, drivers are preferred.

ataradov:
If your device is self powered, it may not need USB VBUS for power, but it still may need it for enumeration,

And also, what do you expect to see on those LEDs? USB has constant SOF packets going, the LEDs will just be driven by a constant 1 kHz signal, so they will be constantly dimly lit.

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