I have a small sketch measuring pulses timing of some external source signals, using D2 and D3.
I have inconsistent results, with glitches, and observed that board is "POWered" even when USB is disconnected.
By POWered I mean POW led is flashing, probably according to data pulses.
Playing more I found that signal on D3 is the culprit, and it happens on all data pins.
The external signals are coming from a chinese unknown IC, supposedly 5V levels.
Is this normal? I mean voltage from a GPIO pin travels through MCU circuitry to the POW LED ?
Do I need a special GPIO buffering to safely read such kind of signals ?
No.
No.
Simply this should not happen.
It might be that something is not soldered up correctly, or that the load on the data pin you are pulsing is too much for the power supply and is causing a brown out.
Read up on ghost powering. The signal of your signal source flows through the protection diodes of a pin and powers the board; it can actually damage your microcontroller.
No just disconnect the unknown IC from the Nano before you disconnect the Nano and connect the Nano before you connect the unknown IC
Thank you, that was... Seems I duplicated this post:
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