When external devices are already powered up and the Arduino is not, a much higher voltage (=5V) than Vdd (=0V) is seen at the inputs, which can easily destroy those pins...
Should use buffers with hot plug capability on that pins
When external devices are already powered up and the Arduino is not, a much higher voltage (=5V) than Vdd (=0V) is seen at the inputs, which can easily destroy those pins...
Should use buffers with hot plug capability on that pins