Component Selection

One thing our team as a whole focused on this week was choosing the correct components for our project. I personally worked on the embedded platform, as well as the specific sensor components for both RFID reading/writing and resistance measurement.

We had already chosen to use a Raspberry Pi Zero for our play areas, and after briefly reviewing the models, I decided that it was worth the extra money to get the newest version with built in wifi. This will allow all the components to communicate wirelessly which will give us a better form factor. It also means we don’t have to worry about using a switch.

I researched e-ink screens and chose one that we could use with the Pi. We needed a screen that was controllable using SPI, and simple enough that I could write a driver for it in a relatively short amount of time. I looked at a number of options that were available in “hat” format, meaning they fit over the Pi, similar to an Arduino shield, but ultimately decided that a naked screen would work best, and allow us to fit it into our play area better. I was able to find one designed to be used with the Pi.

For RFID reading/writing, I looked at projects people had done with a Pi/RFID and noticed that they primarily used a single RFID chip. I researched that chip, found that it would fit our needs, and was able to pick an appropriate module that used that chip. I also assisted Chris with finding cheap RFID stickers that were compatible with the chip (a surprisingly difficult task).

For resistance measurement, our initial idea was to use an RC circuit and measure how long a capacitor with a known capacitance took to charge to a certain level. We could then calculate resistance of that circuit. However after reading more about this method, I had doubts about its accuracy. Instead, I found that there are devices called current shunts that measure current. I was able to find one with an I2C interface that I’ll be able to read using the Pi.

Software Research

Finally, on the software side I began creating a general design, and looking for python libraries to perform the low level tasks required to interface with our sensors and other peripherals.

Once the design is finished (at the beginning of next week) I’ll be able to include a diagram in my status report. Ultimately it will be difficult to evaluate the software libraries until I begin to use them with our hardware, however I chose hardware such that there were multiple library options. Also, in the worst case I can directly write the C to do both SPI and I2C communication.

My progress is on schedule, and I believe our progress as a whole is as well. Finding parts took somewhat longer than we thought but we aren’t off track. We also all have work we can do while we wait for the parts to arrive, which will help to keep us on schedule.

My main deliverable for the next week is a complete diagram of the architecture of the software. It will include the play areas, the central computer, and how they will it be networked together, and it will inform my design for the rest of the project.

As a secondary deliverable, I would like to have written the main game components of the software. This will largely be a state machine for the game and associated code. This was initially planned to be completed during week 3 but in the absence of our parts I will work on it next week.