Assignment 2

Introduction

In Assignment 1, you learned how to get data from the Internet and visualize it. In this assignment, you’ll use your newfound Javascript skills to interact with your Photon; you’ll also learn a bit of microcontroller programming in C.

Goals

The main goal for this assignment is to get comfortable with the idea and process of sending data back and forth from a physical object (the Photon) to a computer. You’ll do this via USB and/or the Particle cloud.

The learning goals for this assignment are as follows:

• Learn how to connect external components to your Photon;
• connect your Photon to your computer for two-way communication over USB or the cloud;
• and become more experienced with Javascript.

What to do

You’re going to connect some extra electronics to your Photon. Have a look at the list of parts that are available to see what you can choose from. In addition, you can order extra parts if you want from Sparkfun, Adafruit or other places; note that “my parts didn’t arrive” is not a valid excuse for unfinished work, though.

Look at the Resources section below. There are a lot of useful links to help you there. Also be sure to check out the Resources on the main page.

Start now! This is a more complex assignment than the first one. I’m here to help but have limited time, so it’s in your best interest to run into problem earlier rather than later!

C-level work

1. Attach a simple sensor to your Photon (for example, the light sensor).
2. Print data out over the serial port.
3. Visualize the data using either your visualization tool from the first assignment (adapted and possibly improved) or another method.

In order to complete this assignment, you will need the supplementary files linked to in the Resources section!

You’ll be graded, in part, on the quality of your visualization; so if you were unhappy with how your first assignment came out, this is your chance to improve it.

B-level work

1. Do the C-level work. Add a second sensor, visualize it too, and improve the visualization to be more interesting/creative than a simple line graph.
2. Adapt it to work additionally with the cloud (using, e.g., Spark.publish()). This means:
   • your B-level code should send data over the serial port and use the cloud-based mechanism;
   • and you should have two kinds of visualizations, one which visualizes the serial port data and one which visualizes the cloud data. (Note that the visualizations can be identical, just pulling from different data sources. They can be two separate files or you can have one file which displays both or allows the user to switch between the data sources.)

A-level work

1. Do the C-level work and the B-level work.
2. Add an output to your Photon. This could be as simple as an LED (note the LED lesson in Resources) or as complex as the Serial OLED display.
3. Have your output react to your computer, via the USB serial port or via the cloud (e.g. via Spark.subscribe() and event publishing). It can react independently to some computer- or online-based event or to the sensors attached to the Photon. In the latter case, however, the data must leave the Photon to the computer or cloud before it returns to cause a reaction.

Deliverables

You’ll turn in your code via your Github repository. Along with your code, upload a Readme.md file, which Github will then display with your repository. Include:

• A description of your circuit: what sensor you used, how you are reading the data from the circuit on the Photon.
• A description of your visualization: what libraries or techniques you used, and what differences (if any) there are from your code in the first assignment.
• A photograph of your completed circuit, clearly showing all of the elements and their connections. Annotations would be nice but are not required.

You will also demo your work in class.

Tips

Network problems

If you can’t get your Photon connected to the network, you can skip that part and use it unconnected. There’s more information here, but the short version is to add the line SYSTEM_MODE(SEMI_AUTOMATIC); at the top of your .ino file. This will allow your code to run right away without trying to connect to the Internet. (Obviously any cloud functions such as Spark.publish() won’t work if you use this solution!)

Resources

Software

• Supplementary files to help with connecting between your local USB port and your web browser.
• If you want to send JSON back and forth from your Photon, check out the SparkJson library, which is included in Particle Build.
• A guide on getting started with your Photon from Particle.

Learning about electronics

• Sparkfun is a great electronics supplier. They have some very nice resources for getting started with understanding hardware:
  • What is Electricity?
  • Voltage, Current, Resistance, and Ohm’s Law
  • What is a circuit?
  • Metric Prefixes
  • How to Use a Breadboard
  • How to Use a Multimeter
  • Connector Basics
  • Polarity
  • Series and Parallel Circuits
  • AC vs DC current
• Sparkfun also has a nice-look set of Photon projects.
• Adafruit also has many useful tutorials, especially under the Arduino category
  • Including a nice lesson about LEDs
• Bildr is a fantastic resource for doing lots of things with electronics and Arduinos. For example, they have a great tutorial on hooking up a light sensor.