John Graham-Cumming

I grew up with Advent Calendars, and they are very common in the UK. Shops across the country sell calendars with typically 24 doors on them, one for each day from December 1 to December 24. Behind each door is a small gift (usually chocolate or something similarly sweet and edible).


The numbers on the doors of the calendar are usually arranged somewhat haphazardly. Part of the fun each day is finding the next door to open. It's the search for the chocolate that makes the calendars enjoyable. Here's an example layout from an Advent Calendar that I bought in Paul in London:


This is an example of a very common 6x4 (and sometimes 4x6) layout for calendars. In this blog I'm going to develop code to find "pleasing" Advent Calendar layouts in the 6x4 shape. But first, here's a little animation of the Paul calendar in action. What makes it "pleasing" is that the numbers don't cluster together (mostly).


So, that calendar isn't bad but it would be n…

If you've read my blog in the past you'll know I like to make ambient devices: mixtures of electronics and physical objects that blend into a home and provide a useful service. I have, for example, a model bus that shows the live times of buses near my home, and a Totoro that shows the weather forecast, and an old candle mug turned into a breathing nightlight using sea glass gathered on a beach.

The Totoro uses an ESP8266 in the form of a NodeMCU for a useful combination of WiFi connectivity, HTTP and GPIO for controlling physical devices like the LEDs in its eyes.

One of the challenges with working with these devices is updating the software on the NodeMCU when new functionality is implemented. Every code change has to be uploaded via a USB cable. For a new project I decided to make use of Cloudflare's Workers product to provide a simple API that tells an ambient device what to do.

By creating an API that just controls the physical aspects of the device (in this case a m…