Im connecting a RPi to a Ardunio Pro Micro board via the serial Tx/Rx pins. This is the first time im building circuits like this so im a little unsure about volts and resistors and stuff.
I am following a picture example from http://blog.oscarliang.net/ctt/uploads/2013/05/arduino-raspberry-pi-serial-connect-schematics.jpg for the resistor set up however this is for a Ardunio Uno and not the Pro Micro. Also people keep talking about plugging in the USB or not. Im not connecting the 3.3v or 5v GPIO pins from the Pi and would like to get power from the USB on the Ardunio and the Pi from the micro USB power socket.
So i just want to clarify before i fry the boards that the resistors and circuits in the picture will still work on the Ardunio Pro Micro (moving the pins to their correct place on that board)
since the Arduino Pro Micro operates at a voltage level of 5V like the Uno, it's serial connection also uses 5V. This means the voltage divider circuit shown in your link works also for the Pro Micro.
If you want you can do the math on your own: Vout = (R2/(R1+R2)) * Vin Vout is the input voltage at the Rx pin of the RPi Vin is the output voltage of the Arduino at his Tx pin R1 is the resistor near to the Arduinos Tx pin (1600 Ohm) R2 is the resistor near to the RPis Rx pin (3300 Ohm)
I hope this helps :)
