This is a weather display for the invisible computers E-Paper smart screen, inspired by E-ink is so Retropunk and ESP32 e-paper weather display.
The filled grey areas in the graphs are probability of precipitation. The vertical bar with the darker background is 3pm to 4pm, when the kids walk home from the school bus. The number is the current temperature. The two clothing icons are what to wear now, and what to wear between 3pm and 4pm. If they're the same, or it's after 3pm, there's only one icon.
The same reason you might cook your own food, or assemble your own PC: you can customize it exactly how you want.
The dashboard is near our closet, and mostly designed to be looked at when you're heading outside. I need to know whether to wear a parka, jacket, raincoat, or just my shirt. I'm also curious whether it will be warm enough later to sit outside and work from the porch, and if so, whether it will be cloudy, rainy or sunny.
And that's about it. I don't care about wind or humidity or barometric pressure or UV index or dew point, and on the rare days when I do, I can just pull out my phone and look at my app.
Aesthetically, I wanted a simple display that contained just the information I desired and nothing else.
Growing up, my father han a LaCrosse weather station that featured an image of a boy (WS-9611U-IT) or worman (WS-9760U-IT) dressed for the current weather, and I liked it so much I got one a few years ago for our house. The problem is, it was just based on the current temperature, so if it was cold and clear in the morning, but hot or rainy in the afternoon, it wouldn't tell you to wear a t-shirt under your jacket or bring an umbrella. So I wanted a clothing icon that would take into account what the kids needed when walking home from the school bus in the afternoon.
Once I had it up and running, there was one other thing I kept wishing to see: the forecast for the next week. And with that, I've been quite happy with the result, and have noticed other people in our household consulting it too.
While I studied two years of electronics in High School in the 1980s (go 7400 series TTL!) and I'm handy with a soldering iron, I was happy to use an existing display and focus on software. Invisible Computers fit the bill perfectly. It's a 7.5" 800 x 480 black and white (not greyscale) display, without interaction, and reasonably priced. Plus, Konstantin at Invisible Computers has been very helpful answering my questions.
My weather app doesn't run on the display itself. Instead, I run it on a web server on an old Raspberry Pi 3 in my home, and a Google Cloud instance queries it once a minute, then forwards the image to the display.
After trying weather.gov, OpenWeatherMap, and tommorow.io, I've settled on Visual Crossing, and I'm quite happy with it. See the Epilogue (below) for details.
You can make 1,000 calls a day to their API. Since there are 1,440 minutes in a day, I implemented some simple caching: if it's been less than 2.5 minutes since last querying, return the previous result.
Perhaps the most important item in the entire display is the current temperature, and it would be nice if I could get the actual temperature from just outside my house, rather than something interpolated from various weather stations that are all miles away. And as I mentioned, I have a LaCrosse weather station which has just such a sensor. Does the wireless format use some proprietary format? Has it been reverse engineered? Yes!
rtl-sdr.com sells a cheap USB dongle that can be used to intercept all kinds of radio signals. I bought the version 3, and followed the quick start and antenna guides.
I had an old Raspberry Pi 3 that I won when I worked at Facebook, for being
first in the Hacktober contest. (In future years, I decided to focus on my work
rather than winning internal contests, no matter how fun.) Anyway, in trying to
set up the Pi, I somehow managed to
destroy a 64 GB microSSD card, but got it work with another. I downloaded,
compiled and configured the driver using the instructions from the "Getting
Started On Linux" section of the quick start guide. To verify it was working, I
installed GQRX (sudo apt-get install gqrx-sdr) and could actually listen to FM
radio on my Raspberry Pi.
The last step was to install and run rtl_433.
Every 50 seconds, it would print the temperature and humidity from my outdoor
weather sensor!
So now that we know the actual temperature, how accurate is OpenWeatherMap's "current temperature"?
They're generally within one degree Fahrenheit, although occasionally differ by
up to about 3 degrees. That's close enough for most people, although I've
gone to the effort of getting the temperature sensor working, so I'll leave that.
But my code, if it doesn't find the rtl_433 executable, falls back on the
API's idea of current temperature.
A simple Python script ties everything together. It runs the webserver, runs a
separate thread which spawns rtl_433 and consumes its output, queries the
weather APIs with caching, and uses Pillow to draw everything in an image.
The four non-rain clothing icons were generated by Bing's Dall-E integration. My son was nice enough to add the rain and umbrella.
The weather icons are from https://uifresh.net/product/weather-icons/.
For weather API, I originally started with weather.gov. The last time I looked into this stuff, in the 1990s, weather forcasting used some of the biggest supercomputers on the planet to do a kind of discrete element simulation of the atmosphere of the entire Earth, that took 12 hours to run. This stuff is only available to governments, so I assumed everybody else was just taking the government's forecast and making it pretty, and I'd rather get it from the original source.
This worked well except for a couple things. When going outside, I want to know the actual temperature now, and whether or not it is actually raining right now. Weather.gov doesn't provide that. The closest it comes is showing you data from the closest weather station. In my case, this is about 5 miles away. But more of a problem is, it only provides data once an hour, so the reported "current" temperature can be up to an hour old. When the temperature changes by 10 degrees F an hour, that can be the difference between "I definitely want a jacket" and "It's too hot for a jacket."
As an aside: it's 2023. Why are we only getting the current temperature once an hour? Like it's still the 1800s and someone needs to look at the level of mercury in a thermometer and write it in a log book or something. I suspect that once an hour was practical when electronic thermometers were new, and since then, "that's the way we've always done it."
Another problem is, I wanted to have a weather icon showing at least precipitation and cloud cover. But weather.gov doesn't have cloud cover in their cleaned up API, only in their raw one, and it would have been more work to dig it out. It does provide a way to get a short and long description of the weather, but both appear to be human generated and aren't easy to map to an icon.
The biggest problem, however, was how unreliable weather.gov is. It goes down (with DNS entry not found, of all things) or times out fairly often. But what finally convined me to change was it was completely down for a week and a half at the end of December 2023.
So I used OpenWeatherMap's API for the weather and clothing icons. However, it only gives the forecast every 3 hours after the first two days, and the weekly graph looked too chunky that way. There's often a steep increase in temperature in the morning or decrease a night, and that was completely obscured with the 3 hour resoultion. If that doesn't affect your use case, OpenWeatherMap still seems like a good option.
tomorrow.io seemed inaccurate. Two days before a big Nor'easter (snow storm), that was all over the news as a sure thing, it only gave an 80% chance of precipitation, whereas other weather outlets were all saying 100% chance. Also, their slack channel, which they say to use for support, was dead, and what they returned in their results didn't match the documentation.
So I moved to visual crossing. Works well, and I've been happy every since!