Block for serial output in GNURadio/GRC - serial-port

Question

I am working on a project that involves GNU Radio/GRC and am not very familiar with the software. I am trying to output data to a serial port in GNU Radio using a block, but have not found a way to do so.
I was wondering if there is a pre-defined block that I can use to put this information to a serial port (USB on a Raspberry Pi 3), or if I had to create my own block. And if I had to create my own block, what that code would look like.
I have been able to write the data to a file using the File Sink to make sure I was getting data, and was wondering if the fix is something as simple as changing the File sink to an serial port sink. See picture below:
http://imgur.com/a/BdaMZ
I also did some research and found a github repo that looks like what I need -- unfortunately, the repository that it links to is no longer there. It did mention using pyserial, which is what I believe is meant for creating my own block in python. The link to this repo is below:
https://github.com/jmalsbury/gr-pyserial

Answer 1

… was wondering if the fix is something as simple as changing the File sink to an serial port sink.
Yes! Or No, it's even easier:
So, in fact, you could even simply use your file sink to write to e.g. /dev/ttyS0 (or /dev/ttyUSB0, or whatever is the device name of your serial port), but you'd have to set up the serial port to work like you want it to separately first. A way of doing that would be using stty, e.g.
stty -F /dev/ttyS0 115200
prior to running your flow graph.
Note that practically all in your flow graph point points to you not being sufficiently proficient with GNU Radio to successfully exchange data. I can't cover everything here, please read the official Guided Tutorials, but:
In a flow graph like yours, where the IO is the inherently rate-limiting element, you must not use "Throttle". Throttle is really just a tool to avoid a flowgraph consuming all your CPU (and to slow down simulations)
Giving your files a .grc ending is bad practice, as that is the ending reserved for GNU Radio flow graphs.
Giving it a .txt ending is plain misleading, since there's no text involved whatsoever. The "file format" (I wouldn't even call it a format) is really just plain binary numbers, as your computer handles them; not decimal ASCII representations of these floating point binary numbers
I also did some research and found a github repo that looks like what I need -- unfortunately, the repository that it links to is no longer there. It did mention using pyserial, which is what I believe is meant for creating my own block in python. The link to this repo is below:
Don't know what you're referring to, https://github.com/jmalsbury/gr-pyserial is perfectly existing!