Can one use the USB serial as an interface (USB-serial in a PC) to communicate with the program? I will need/will be using the onboard serial for another purpose/connection and need both.
Hi myers5721,
If you try to use the hardware UART/USB on the RedBoard with another device on that same bus (D0 and D1), you will most likely run into what is called Bus Contention. We cover this in some more detail in our [Serial Communication tutorial in the “Common Pitfalls” section.
If you want to use a serial device with your RedBoard while also using the USB/HW UART, I would recommend using the [SoftwareSerial library. That allows you to assign two available digital pins on your Arduino to create a second serial port. We use this library all the time on our boards to prevent bus contention as well as protecting firmware on devices like our Serial Enabled LCDs from being corrupted by data sent over the Hardware UART. The SoftwareSerial library does have some limitations but for simple serial communication between an Arduino and another serial device, it works really well.
I hope this helps explain what issues you will run into and points you to a potential workaround for your project.](https://www.arduino.cc/en/Reference/SoftwareSerial)](https://learn.sparkfun.com/tutorials/serial-communication)