Skip to main content

A Totoro to forecast the weather

Regular readers may know that I like ambient devices: devices that fit into the environment unobtrusively and provide information at a glance. One such device is my bus monitor that shows times of buses at the stop near my house.

Recently I decided to solve the problem of answering the question "Do I need an umbrella?" when I leave the house. For this I chose to use an ESP8266 in the form of a NodeMCU running Lua and display the coming weather by illuminating the eyes on a small Totoro figure.

This was my first NodeMCU/ESP8266 project and there's definitely a bit of a learning curve. I ended up using luatool to upload my Lua code to the device, and esptool to flash the firmware using a custom firmware build from this wonderful website with the following modules present: cjson, file, gpio, http, net, node, tmr, uart, wifi, and ws2812.

./ --port /dev/cu.SLAB_USBtoUART write_flash -fm qio 0x00000 nodemcu-master-10-modules-2017-04-08-20-28-08-integer.bin

The first step was to prise open the Totoro figure and then drill out the eyes so that two LEDs cut from a NeoPixel strip could be hot glued in place.

I made a mess of opening the bottom of the Totoro as I didn't realize there was a large chunk of resin in the bottom (for stability). However, I ended up with a nice hole through which it's possible to connect a USB cable for reprogramming the NodeMCU.

The rear part of the Totoro contains the NodeMCU with just five wire connections: power, ground and data to the NeoPixel strip, and a pig tail to supply power through a hole drilled in the back (5V from an old wall wart I had lying around is fed straight to Vin and GND on the NodeMCU).

I used heat shrink tubing to insulate the connections so that there aren't any inadvertent short circuits when the Totoro is closed.

The code that runs Totoro is here. It uses the Met Office's DataPoint API to get the weather forecast for a location in the UK. You'll need to register there for an API key and figure out the location you want to get weather for from the Met Office data. As coded it gets the weather forecast for a maximum 6 hour period (two 3 hour forecasts) and figures out the worst weather to happen during that time.

The configuration for the Totoro is all in totoro-config.lua where you'll fill in the weather location, API key and the credentials for the WiFi network you want your Totoro to connect to.

The Totoro conveys the following with its eyes:

  • Red: heavy rain
  • Blue: rain
  • White: snow
  • Flashing white/black: hail
  • Yellow: sunny
  • Flashing red/blue: Internet or API connection problem
  • Flashing green: updating weather forecast
  • Black: no special weather
Here's Totoro having trouble reaching the API (flashing red/blue).

And here's Totoro checking the weather (flashing green) and finding that it's nothing special (goes black).


Unknown said…
Incredible Totoro-T1000! :)
Inspired by you, I am thinking about robotizing my Android-G-Cloud doll.
Could you tell me the size of your Totoro? Guessing it from your photos is hard.
It's this figurine:

About 10cm tall

Popular posts from this blog

Your last name contains invalid characters

My last name is "Graham-Cumming". But here's a typical form response when I enter it:

Does the web site have any idea how rude it is to claim that my last name contains invalid characters? Clearly not. What they actually meant is: our web site will not accept that hyphen in your last name. But do they say that? No, of course not. They decide to shove in my face the claim that there's something wrong with my name.

There's nothing wrong with my name, just as there's nothing wrong with someone whose first name is Jean-Marie, or someone whose last name is O'Reilly.

What is wrong is that way this is being handled. If the system can't cope with non-letters and spaces it needs to say that. How about the following error message:

Our system is unable to process last names that contain non-letters, please replace them with spaces.

Don't blame me for having a last name that your system doesn't like, whose fault is that? Saying "Your last name …

Importing an existing SSL key/certificate pair into a Java keystore

I'm writing this blog post in case anyone else has to Google that. In Java 6 keytool has been improved so that it now becomes possible to import an existing key and certificate (say one you generated outside of the Java world) into a keystore.

You need: Java 6 and openssl.

1. Suppose you have a certificate and key in PEM format. The key is named host.key and the certificate host.crt.

2. The first step is to convert them into a single PKCS12 file using the command: openssl pkcs12 -export -in host.crt -inkey host.key > host.p12. You will be asked for various passwords (the password to access the key (if set) and then the password for the PKCS12 file being created).

3. Then import the PKCS12 file into a keystore using the command: keytool -importkeystore -srckeystore host.p12 -destkeystore host.jks -srcstoretype pkcs12. You now have a keystore named host.jks containing the certificate/key you need.

For the sake of completeness here's the output of a full session I performe…

More fun with toys: the Ikea LILLABO Train Set

As further proof of my unsuitability to be a child minder (see previous post) I found myself playing with an Ikea LILLABO 20-piece basic set train.

The train set has 16 pieces of track (12 curves, two straight pieces and a two part bridge) and 4 pieces of train. What I wondered was... how many possible looping train tracks can be made using all 16 pieces?

The answer is... 9. Here's a picture of the 9 different layouts.

The picture was generated using a little program written in Processing. The bridge is red, the straight pieces are green and the curves are blue or magenta depending on whether they are oriented clockwise or anticlockwise. The curved pieces can be oriented in either way.

To generate those layouts I wrote a small program which runs through all the possible layouts and determines which form a loop. The program eliminates duplicate layouts (such as those that are mirror images of each other).

It outputs a list of instructions for building loops. These instructions con…