If you load an empty program in your arduino, and make the folowing connections:

Pi --> Arduino

Pin 8 --> Pin 1

Pin 10 --> Pin 0

Gnd --> Gnd

than you should see your linux console in the arduino serial program is you set the baudrate to 115200.

This method will work for the raspberry pi models without wifi. On the wifi models the pins on the pi will be different.

If you load an empty program in your arduino, and make the folowing connections:

Pi --> Arduino

Pin 8 --> Pin 1

Pin 10 --> Pin 0

Gnd --> Gnd

than you should see your linux console in the arduino serial program is you set the baudrate to 115200.

This method will work for the raspberry pi models without wifi. On the wifi models the pins on the pi will be different.

The Arduino uses FTDI usb-to serial converter. This converters uart side is connected to the AVR-chip via pin 0 and 1. If you load an empty program in your arduino, it wil not use these lines. Now you can connect directly to the FTDI chip thru this pins. The converter does not care if it is communicating with the arduino or the pi over these lines.