I have a board that is constantly printing information I need to its serial port. I am curious as to how I could connect the arduino to it (presumably through pins 0 and 1?) and get the serial readout from the other board. Both the arduino and the other board will have their own dedicated power supplies, I am just a little unsure of exactly how to go about it both in terms of physical connection and code. What I was planning (and won't do until being advised by the wisdom here) is directly connecting the RX and TX pins of both devices, and using the softwareserial library to read the data
The Tx of the other device should go to Rx of the Arduino and vice-versa. Unless you are planning to use the hardware serial ports for something else, hardware serial (pins 0 and 1) are more reliable than software serial. Also connect the Gnd pins of both devices.
Also what voltage levels does the other device use? TTL? Or RS232? You can tell somewhat by putting a meter on it. If it reads around +5V when idle it is TTL. If it reads around -10V then it is RS232 and you will need a level shifter.
I am not sure but I think it uses RS232. How do I use a level shifter to interface the two?
EDIT: I put a meter on it and I was getting around -6.5v