Serial Link Between 3.3V devices

Question

I have an RPi and a freescale FRDM-KL25z controller which will talk over serial protocol. I'm using the pyserial library on the pi:

import serial
ser = serial.Serial('/dev/ttyAMA0', 9600)
ser.write('hi FRDM')

and using the serial protocol from the mbed library will generate interrupts to process the data from the Pi.

https://developer.mbed.org/users/mbed_official/code/mbed/docs/4fc01daae5a5/classmbed_1_1SerialBase.html#ae67fb9b5a2ee2f4e98a39cdab10ed090

My question is, having two devices which talk over the same protocol at the same potential and in close proximity, do I need a logic level converter or some form of UART chip?

I would think not, but I am aware that RS232 is a +-12V protocol so would just like to ensure that this assumption is correct.

Answer 1

If both share the same logic levels (0V-3.3V) and the same ground it shouldn't be a problem. But then you aren't using RS232, just UART. The Serial bridge on the Arduinos works the same way. The FTDI chip uses 0V-5V and the ATmega uses 0V-5V.