This project started when I invested in a quite expensive coffee machine for my home. I took the amount out of my savings account as an investment. Then I wondered, how long would it take to pay it back to myself if I were to pay Starbucks prices for my coffees every day.
This project uses Bunq and an ESP32 (with giant button for fun!) to pay myself 2 euros every time I drink a coffee.
Due to the quite important part of having a good TLS stack (and lack of a good C library) I added a backend service in Go that does the actual transaction. This code is in Go and in backend/
I used an Adafruit Feather ESP32, which has a Cherry switch connected from A0 to GND. For fun it is inside a 3D printed panic button. The ESP32 is setup to go into deepsleep and has an interupt when A0 goes low to connect to the WiFi and call the backend to make a payement.