The Chicago Machine

This projects holds the source code for @gnarmis and @lukeshepard's robot for Robot Riot January 2019 in Chicago.

• System Design –– the full system
• Website –– Next.js + Firebase
• Raspberry Pi –– custom "taunting" scripts + Twitch.tv streaming

System Design

Regular whiteboards and the SketchPaper iOS app were great tools, along with just meeting regularly. We went through a lot of sketches, prototypes, and video updates of individual explorations.

This was our first real build, so we made paper and cardboard prototypes, bought servos and basic batteries, stayed at 6 volts for electronics, went to physical stores and talked to vendors for advice, and figured out what worked and what didn't. I even checked out the Chicago Public Library's Maker Lab, which provides very accessible 3D printing for like $1 per 30 min job –– along with educational resources. Also, fried some components and boards lol.

Some things we learned:

• Simpler is better. We decided to do basic RC for motion control and raspberry pi for the fancy features like video streaming. This was super helpful when the raspberry pi's WiFi-based control mechanisms started flaking out because of various WiFi/cell hotspot issues.
• Grip, speed, basic design: these factors will make the difference.
• https://www.servocity.com/actobotics is awesome. Wish we'd found it sooner.
• Explore, test, explore some more. Our final design was built within a day of the competition –– maybe too close but in the meantime we'd figured out how much time we'd need and were a lot more confident in what we could build (by building again and again, often from scratch).

Website

The website is a small webapp where we hooked up a Twitch.tv stream coming from the robot, along with some crowd-pleasing voting functionality.

I chose to use Next.js and Google Firebase, both somewhat new to me. I wanted rapid prototyping and minimal fuss. There two tools ended up being perfect! It was a bonus to find already existing third party packages that made it even easier to integrate Firebase with React code.

The two main pages and what they demonstrate (stuff you can cannibalize for your own prototyping, in other words):

• Root/index page: a Twitch.tv stream with some realtime voting buttons
  • How to consume Firestore data in a realtime way, using some community packages
  • How to create Firestore data on a button click
• Soundboard page: a kludgey audio file upload and playback page that we abandoned
  • How to do basic Google oAuth Sign In using Firebase with minimal custom UI/logic work.
  • How to use Firebase Storage (like Amazon S3)
  • NOTE: did you know there's no API to get back download URLs???!!! I had to make a collection in Firestore just to store download URLs!

Caveats:

• There are some edge cases with configuring the firebase library on page load more than once. I think the Soundboard page in particular has some issues for sure, though it allows sign ins, uploads, and playback.
• The Firestore rules we have to control who can do what are very basic. Consult Firebase docs to figure out how to properly handle them.

RaspberryPi

Our RaspberryPi 3 B+ didn't directly control the servos –– we used a separate RC controller with a received board that was hooked up to power and servos.

The code here enabled Twitch.tv streaming, and bootup and taunting sounds. After a bit of exploration, implementing these as systemd services ended up being the most practical solution: predictably launching on boot, and starting/stopping really easily on the fly.

Some of the related files have been provided. See ./bootstrap.sh to see a portion of the setup we did.

Some things we learned:

• Make sure to update the password, I did that on first launch

• With an ethernet cable, you can do headless SSH

• The hostname of a computer plus .local will resolve to that computer in the local network. No need to hunt for IP addresses. Also, a good reason to define a custom hostname. Ours was the-chicago-machine.local for eg.

• If you supply a properly configured wpa_supplicant.conf in the SD card's boot drive in the root directory after burning raspbian OS on it, the raspberry pi will automatically configure itself with those WiFi settings and connect to that WiFi network. Here's my config minus the password:

    country=US
    ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
    update_config=1
  
    network={
        ssid="A Momentary Lapse Of Sanity"
        psk="the_password"
        key_mgmt=WPA-PSK
    }
  

• rpi ships with RealVNC already. Enable it with raspi-config and then connect with a VNC client. You'll get a full graphical desktop this way.

• vcgencmd get_camera to determine if camera is supported or detected. raspi-config to enable camera and reboot. raspistill -o test.png to test camera capture.

• You can force audio to come out of the audio jack with raspi-config

• That @#$@#$!! camera ribbon cable is the worst. But workable.

• Know how to forget a WiFi network on Debian!