So I have been working on a project that requires both an Arduino and a Raspberry Pi. Arduino for real-time adjustments, Raspberry Pi for video streaming and connecting to a server were it will get commands. My issue has been trying to have the Raspberry Pi communicate to the Arduino over Serial. In a perfect world I would have used USB to USB and it would have worked but my Raspberry Pi wont recognize it unless it is on a powered USB hub so I am beginning to think power is my issue. I attached a rough diagram to the post. It goes Battery(11.1v) → Arduino & 5 Volt Regulator. The Regulator feeds power to the raspberry pi. Then a USB cable goes between the Arduino and raspberry pi. This only works if I use a powered USB hub. Why? is their something wrong with my grounding.
Don't think it's a GND connection. Then the USB cable itself would fix it. But what is powered by the Arduino? The Arduino can hardly deliver any power when powered from 12V. Why not just power the Arduino from the 5V as well?