# About

While setting up some basic home automation, I realized that there things that I'd like to track simply by pressing a button. For example, has anyone fed the dog this morning? She's more than willing to ask for breakfast even if she's already eaten it :)

While searching for a good product for this, I couldn't find one, so I decided to make my own. The primary goals are:

1. It must be cheap, ideally around \$5.
2. It must be reasonably manufacturable (on the order of 10s to 100s).
3. It must be re-useable, no tossing it when the battery dies!
4. It must reasonably small and inoffensive.
5. It must integrate with HomeAssistant, ideally with minimal configuration.

Unfortunately, shortly after I ordered my first rev of PCBs, Ikea released the $10 [Shortcut Button](https://www.ikea.com/ca/en/p/tradfri-shortcut-button-white-20356382/) which meets most of my criteria. Falling victim to the sunk cost fallacy, I plan to see it through to making a few of these.

# Q&A

## Why are there two microcontrollers?

Cost and ease of development. 

Both ESP8266 and ATTINY(2/4/8)5 modules can be had for around \$1 each, and
there are retail programming jigs available. I have a kid now and don't want to
spend my time making a programming board.

The ESP8266 alone cannot really wake from multiple sources and know trap the
source of the interrupt- there is only one pin that can wake up the micro from
deep sleep, and that same pin needs to be used if you want to use the RTC as a
wake source. Sure, you could use an OR-gate and also wire each source to a GPIO,
but you might miss the source by the time the ESP wakes up to check the pins.

Hence, the ATTINY is used to capture the wakeup and inform the ESP8266, who does
the heavy lifting.

### What about ESP32?

The cheapest modules I can find at the time of writing are around \$3.50 apiece,
and they can be power hungry (spikes up to 750mA compared to 400mA, from what I
read).

### What about ESP32-S2?

They appear promising and are only \$2 per module on Digikey at the time of
writing, however they are not supported by platformio yet.

### What about ...?

I probably wasn't aware that it exists.

# Development

The standard PlatformIO tooling should work. However, here's a bit of setup I had to do in order to make emacs+clangd happy:

``` sh
cd <PROJECT_DIR>
# Create the compile_commands.json
pio build -t compiledb
# Link the compile_commmands.json from the git root, which is where tools are expecting it
ln ./.pio/build/<ENV>/compile_commands.json ../../compile_commands.json
```