pylon:
I don't understand your pin configuration diagram. What are the colors for? What do the key terms mean? They are not the Mega2560 pins, aren't they?
Those are the pins of the datalogger. The colors mean nothing. The sensor goes to those pins.
To emulate the sensor, I will disconnect it. Then, I need to connect the Ardunio pins to those pins. They're GPIO (not SPI--because only two lines are connected for each ultrasonic sensor).
pylon:
You just have to write the correct bytes to the corresponding serial interface. Try to do that, post your code and tell us the problems you might have. Don't expect us to write the code for you.
That helps a little. My main question is how do I output a certain distance. For example, what distance is 0.5 feet (0.15m)? I will continue looking into the SoftwareSerial library...but I still have a very vague idea on where to go from "just have to write the correct bytes."