connect from r-pi 3 to arduion , the arduion restart

hi guys
i'm programming with arduino pro and r-pi 3
i connect the arduion and the pi vi usb

every time i run the python command : ser = serial.Serial('/dev/ttyUSB0', 9600)
the connection make my arduion to reset for sec , every thing works fine after (i can run any command )
but i most avoid this reset ....
the arduin have is on power 5v
i try to connect only the wires without the 5v and ground from the pi
but the connection didn't work ..
how can i fix it ?

every time i run the python command : ser = serial.Serial(’/dev/ttyUSB0’, 9600)
the connection make my arduion to reset for sec , every thing works fine after (i can run any command )
but i most avoid this reset …

If you are using a USB to connect the 2, I don’t know the Arduino pro, but on many Arduino compatible boards opening the serial port causes an automatic reset. On those boards there is usually a way to disable auto reset by cutting a trace on the board. Another way is to install a capacitor (10uf) from reset to ground. Google “arduno disable auto reset”.

i try to connect only the wires without the 5v and ground from the pi but the connection didn’t work …

You must connect the grounds, but not 5V. Are the pi inputs 5V tolerant?

i don't know how .... but it work ....

your the best !!!

tnx