the what
this is the 88x31! it's a bit dense, but that's because it contains all the battery
statistics present on the homepage.
- the 7 horizontal bars on the left show the weekly statistics: each column
represents an hour, which can be either empty, half-full, or full, to indicate the
charge in increments of 33%.
- the top 2 bars on the right are the 24-hour low and high charges.
- the bottom bar is the charge at time of button generation.
if you want to embed it, please hotlink! the image is updated by a cronjob,
so the button will change over time on reload.
the original tga is available at /88x31.tga, and the
machine-readable data (see below) is available at
/88x31.txt.
the how
recently, I've been playing with uxn. it's a
similar sort of idea to PICO-8 or other fantasy consoles, but instead of using a
conventional programming language, it's based around this 16-bit stack-based assembly
language, which is intended to be comfortably handwritten. it's very cool, and very fun.
I thought the design ethos of "doing a lot within extreme constraints" that uxn has fit
well with compost.party's whole vibe, so I decided to write the button generation code in
it. the resulting rom (uxn programs are binary rom files) is 1.5kb, generated from 480
lines of uxntal code.
input data
the uxn code works by stepping through an internal state machine, and reading in numbers as
it goes. it ignores any character not in the digits 0-9, treating any such sequence as a
delimiter between numbers. input numbers are not capped, and overflows are not checked,
because it's not necessary for the sort of input data.
the actual format, then, is just a list of numbers. the first 3 are for the current
statistics, followed by 168 numbers composing the weekly statistics. here's what that looks
like:
current: 99
recent low: 00
recent high: 00
past week:
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
output
GIF compression is absolutely implementable in uxn. at some point, I will probably do
compression in-rom! unfortunately, I am lazy, so currently the script outputs a .TGA file.
TGA is an image format with support for a frankly astonishing number of modes, one of which
is uncompressed, with a palette. this makes it easy to have the internal buffer that the
button gets generated in be the same format as the TGA output. the rom basically just
updates a buffer where 1 byte = 1 pixel, and then spits it out to stdout. that can then be
converted to a more conventional format, like GIF.
plumbing
getting the input data isn't too hard. the history is already aggregated for the purposes
of the compost.party homepage, and GIF compression can be easily handled with a tool like
imagemagick. orchestrating all of this is accomplished in bit of bash:
#!/bin/bash
# convert the data into a list of hourly numbers
# this code is needed to fill in gaps where the phone was dead
node <<EOF >/tmp/buttonstats.txt
let start = Date.now();
let powerdata = Object.fromEntries(
require('/home/ursula/git/compost.party/src/_data/power-history')
.filter(val =>
val.timestamp.includes(':00:'))
.map(val =>
[val.timestamp.substr(0,13), val['qcom-battery'].capacity.value]));
for(i = 0; i < 168; i++) {
key = (new Date(start - (i * 3600000))).toJSON().substr(0,13);
charge = powerdata[key] ?? 0;
console.log(String(100 + charge).substr(1));
}
EOF
# parse out the main readings
current=`cat /sys/class/power_supply/qcom-battery/capacity`
low=`tail -n 24 /tmp/buttonstats.txt | sort -n | head -n 1`
high=`tail -n 24 /tmp/buttonstats.txt | sort -nr | head -n 1`
# generate input for the rom
{ echo "current: $current"
echo "recent low: $low"
echo "recent high: $high"
echo
echo "past week:"
echo `cat /tmp/buttonstats.txt` | fold -sw72 | sed 's/^/ /'; } | tee ~/html/88x31.txt |
# generate and store the image
uxncli ~/88x31.rom | tee ~/html/88x31.tga | magick tga:- ~/html/88x31.gif
# template the webpage
sed 's![0-9].*$!<b>\0</b>!g' ~/html/88x31.txt |
cat ~/html/button.head.html - ~/html/button.tail.html >~/html/button.html
rm /tmp/buttonstats.txt
can I see the code?
of course! it's free to read and modify
on the compost.party git!