I will preface this post by admitting that my research into the problem is preliminary at this stage, but having not easily found the answer, I hope that this post can be of use to somebody in the future.
I am attempting to use an Arduino Uno to interface with an iRobot Create 2 robot. The robot can communicate via serial port, which works at TTL levels(0-5V; 0V being 0, and 5V being 1). I have chosen to use the SoftwareSerial library (http://www.arduino.cc/en/Reference/SoftwareSerial) because my project necessitates the use of a software serial port.
I am having difficulties reading data from the Create robot using the Arduino, and I have performed signifcant testing to determine that the problem is with the serial communication. I need to know what levels the software serial port on the Arduino expects. Does it use TTL levels, or something else?