Nano v3 logic analyzer (problem?)

Hello :) I have one Nano v3, i've uploaded the logic analyzer schetch then i have connected:

  • The GND of the nano to the GND of one I/O board.
  • Pin 8 to pin 12 of the nano to a 1k R then to the pin i want to analyze.

If i turn on the I/O board the PWR led on the Nano turn on... But the USB is unplugged and there is only the GND connected, there is nothing on the vIN and +5v Why the PWR led turn on ?

Most probably the current through the data lines is sufficient to light the power led.

Please note that you can damage the MCU by signals exceeding Vcc. You should always power on the Arduino first, then the other boards.

Though the 1k resistor will likely prevent damage.