Bubbler 💭

Drink machine implementation in Rust for the meme

Usage

We've historically used Raspberry Pis. These instructions are tested against 2021-05-07-raspios-buster-armhf-lite.img using what I can only assume is a Pi 3.

God help us.

GPIO Hardware description

Bubbler expects every peripheral to be active-high:

• When the machine is stocked, current should be allowed to flow through the switch.
• When the machine is dropping, the vend pins are energized.

Something worth noting is that some Raspberry Pi pins start pulled high. Here's a list.

For Big Drink, we uses pins 9-15 for the vend motors, 17-23 for the stocked switches, and pin 16 for the latch relay (optional).

The latch pin gets pulled high for 1 minute after every drop. It's intended to prevent motors from burning out if they get jammed.

In Big Drink, we use a relay, which allows us to cut power to all the motors when they shouldn't be running. Note that this isn't a cutoff for the vend pins (that wouldn't be very useful), but rather the power source for the motors.

Boneless supplied a wire diagram.

Initial setup

Note: These steps only matter for 1-wire machines

1. Run raspi-config and enable I2C and One-Wire interfaces... Make sure to change the root and pi users' passwords!
2. Install owfs: apt install owfs
3. Modify /etc/owfs.conf and add the 1-wire HAT: server: i2c = /dev/i2c-1:0
4. Also make sure mountpoint = /mnt/w1 in owfs.conf. Create /mnt/w1 if it does not exist.
5. Reboot!

Bubbler install

Install rust using rustup:

curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

Grab a copy of bubbler:

git clone https://github.com/ComputerScienceHouse/bubbler

Build bubbler:

Compilation

cargo build --release

Cross compilation

Bubbler supports cross. To cross-compile for ARM, simply run

cargo install cross
cross build --target=armv7-unknown-linux-gnueabihf --release

Copy .env.example to .env. Make sure to modify it for your machine.

Drop this systemd unit into /etc/systemd/system/bubbler.service:

[Unit]
Description=Bubbler
After=network.target
Requires=owfs.service # Only needed on 1-wire systems. Remove otherwise.

[Service]
Restart=always
Type=simple
WorkingDirectory=/root/bubbler
EnvironmentFile=/root/bubbler/.env
ExecStart=/root/bubbler/target/release/bubbler


[Install]
WantedBy=multi-user.target

Nginx setup

We use nginx to provide SSL termination with certbot.

First, install nginx and certbot:

apt install nginx certbot python3-certbot-nginx

Disable the default config:

rm /etc/nginx/sites-enabled/default

Make a new config for bubbler at /etc/nginx/sites-available/bubbler:

server {
    listen [::]:80;
    listen 80;

    server_name littledrink.csh.rit.edu;

    location / {
        if ($http_x_auth_token != "DRINK MACHINE TOKEN GOES HERE") {
            return 403;
        }
        proxy_pass http://127.0.0.1:8080;
    }
}

Enable the config: ln -s /etc/nginx/sites-{available,enabled}/bubbler

Fetch a certificate by running certbot. Make sure to enable redirects.