[En-Nut-Discussion] ground difference

[emjay]

i have an ethernut 1.3 supplied by 12 V

why is there a diffenrence between the grounds (GND and supply ground) 
of ~0.8V?
how can i realize a measurement (INT0) of an external rectangle signal 
0-5V, without connecting (shortening) the grounds (GND and ground of 
rect.=supply ground)?

thx emjay


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