Week 12 Assignment: Interface and Application Programming

Write an application that interfaces a user with an input and/or output device that you made.

Based on my lessons learned from week 5, I designed and fabricated a new PCB incorporating a MOSFET and a potentiometer to control a 5 V DC motor. The board also included a SAM D11C microcontroller, 10-pin programming header, and connection jumper to receive external signals. I designed this board in Eagle through Fusion 360. Adding the potentiometer was a significant modification from my week 5 board.

Adding the potentiometer to the broad was a major modification. I had to create a new component in Eagle with the correct footprint and pin designation. See Takeaways section for link to a guide on creating a component in Eagle.

My final board design is hyperlinked to the image to the left.

The PNG trace and outline files for both boards are hyperlinked below.

To reuse a piece of stock I had to mill along a board edge. Even with tape adhering the board edge to the bed, it still deformed too much for the copper layer to be completely milled through.

To correct the unmilled traces I thought about re-milling the entire board with a slightly deeper cut depth or resetting the z-axis for this region of the board, but did not based on time constraints and concerns of possibly pulling up traces during a second run. Instead, I created a .PNG file with only the unmilled traces and took a look at it in mods. I immediately realized this wasn't going to work, because it was going to mill through my existing traces. I decided to pull the board off and conduct board surgery while weeding.

Weeding was painfully tedious, but was successful after scorning along the missing trace edges with a razor blade and slowly peeling away the excess copper.

Post Milling

Weeding

Weeded/De-Burred

Final Product (Top)

Final Product (Bottom)

I was all over the road on how I was going to develop a graphical interface to depict potentiometer position. I started by looking into TkInker, because I already had Python installed on my computer to run several scripts developed by cohorts in my lab. This is how I stumbled across the Python GUI shown section 12.1. There is no lack of information on the internet, and I started to feel a little overwhelmed by the number of forum posts for Python serial port reading. I decided to pivot away from Python and towards web-based XML format GUIs developed from scalable vector graphics (SVGs), because most of Neil's examples used this and I had grown more comfortable with .HTML format while creating this web site.

Using the SVG tutorials located here, I developed the gauge display to the left. The .HTML file for the graphic is hyperlinked to the image. After realizing I would need to use an intermediate program to create a serial port connection, I decided to pivot again. This time I moved on to using the coding platform, Processing, based on feedback from Anthony and Hannah's presentation during class.

After downloading the Processing application, I reviewed the below list of Processing examples and tutorials.

Hannah's Fab CBA Site - LINK
Fab Academy Site - LINK
Russett's Fab Academy Site - LINK
Cusco's Fab Academy Site - LINK
Processing Examples - LINK
Processing Reference - LINK
Processing Forum - LINK

After recognizing similarities between these examples and how to read a serial input, I developed a graphical display that scrolls based on potentiometer position. The code is hyperlinked to the image to the left. The code establishes a long series of pixel squares that scroll across the display window. The scroll direction and speed are based on the potentiometer input from a serial port. The below video shows this code in action.

I hope to revisit my original objective of creating a gauge to depict potentiometer position in Python using TkInter, now that I have a better understanding of reading from a serial port to create movement in an object.

In Eagle, this link provides a step-by-step guide for creating a component library.
In Eagle, to create a heat sink via a thermal pour that connects to a component pad, the polygon pour must have the same name as the component's pad.
To assist with debugging use the 'println' command to verify input/output values.