The Badge

A round screen you wear. It runs about a day on a charge, wakes to a clock, and does a handful of things well rather than many things badly.

Flash it from your browser Source on GitHub

Why not the firmware it came with

It started as one thing. I wanted an air mouse — driving a PC from a phone over RDP means toggling between touch and pointer mode forever, and I wanted a physical thing that simply pointed. Everything else here arrived after that.

• Things I would actually reach for. A clock, a timer, a recorder for meetings, a calculator, the F-keys a phone keyboard does not have. Not a tour of what the hardware can do.
• No voice, no chatbot. The demos written for this board lean on voice assistants and LLM chat. On a 1.75-inch screen with no keyboard I would use that twice and never again, so none of it is here.
• Some of it is just taste. The water, the orbs and the games are not useful and are not pretending to be. They are in because I like them.
• And the power. None of Waveshare's own ESP-IDF examples turn on CONFIG_PM_ENABLE or tickless idle, and the one example that shuts down the twelve unused AXP2101 rails is not the path the board support package takes — so a build started from them leaves the CPU awake and a dozen regulators switching into nothing. Here the panel is really switched off rather than covered, the chip light-sleeps between frames, and two rails are left standing. Together those took standby from 11.9 hours on a charge to 19.6.
  Both of those are measurements of this firmware, before and after that work — the firmware the board shipped with was never put on a meter here. The claim about the examples is about their published source, which anyone can check.

What it does

Open-source firmware for the Waveshare ESP32-S3-Touch-AMOLED-1.75C — a 466 × 466 circular AMOLED in a milled aluminium case, with a touch panel, an accelerometer and a gyro.

It is meant to be worn, so the default orientation is turned 180°: put it on a strap and the panel's own top ends up pointing down your arm, and that rotation is what leaves the screen the right way up on a wrist.

Trackpad & Air Mouse

Bluetooth HID. Use the face as a touchpad, or lift it off the desk and point — the gyro drives the cursor from there.

Excel keys

A phone's soft keyboard has no F keys, which is the real reason an Excel formula cannot be touched over RDP from a phone. Twelve of them in a ring, fired over the same Bluetooth link.

Calc

A 4 × 4 grid loses its corners on a round screen, so the digits stack in three columns down the middle and the operators take the left and right flanks — which is where the room actually is.

Water

380 particles of smoothed-particle fluid in a round tank, run by the accelerometer, with a boat that rides whatever surface they make. Tilt it and it pours.

Orbit

The Moon, the Earth, Jupiter and the Sun, turned by hand. The maps are NASA imagery; delete them and each body falls back to being drawn in code.

Recorder

16 kHz IMA-ADPCM straight to flash, about 52 minutes of it. Plug the badge in, press export, and it re-enumerates as a read-only USB drive full of .WAV files.

Settings

Brightness, sound, screen-off delay, time zone, Wi-Fi and Bluetooth pairing. Every row carries its own value, so nothing has to be opened just to be read.

Four ways of watching time

Clock, timer, stopwatch and alarm are all one app — they are the same kind of thing, so they are four screens swiped through vertically rather than four icons on the home screen.

Clock

Seven segments drawn as shapes rather than a bitmap, so it is sharp at any size. Date, seconds, battery and uptime underneath. The lock screen is the same face, unlit.

Timer

5, 15 or 25 minutes to start from. What is left is a ring closing rather than a number to read — the one thing a round screen does better than a rectangle. Tap to start, hold to reset.

Stopwatch

Here the digits are the point, so there is no ring. Hold to take a lap. Every character gets a fixed-width cell of its own — in one centred label a proportional font makes the number shiver.

Alarm

It is watched by the launcher, not the app, so it still rings with the app closed. And it stays quiet until the clock has been set: judging seven in the morning against 1970 would fire the moment you plugged it in.

Games

None of them cost much — each moves a handful of shapes. Three of the four are played by tilting the badge, which puts an IMU that is sitting there anyway to work.

Bricks

A paddle that runs along the bottom arc and bricks laid round the circle — a shape a rectangular screen cannot make. Five levels, and three balls, because losing all of it to one miss is where people put the badge down.

Pinball

The round screen is the table. Bumpers, drop targets, and a flipper at each end of the bottom arc — tap the left or right half of the screen to swing them.

Marble

Tilt to roll it. Drop it in the hole and the next hole appears somewhere else. Nothing to it, which is the idea.

Pop

Bubble wrap. They pop on the press rather than the release, which is the whole difference between it feeling right and feeling wrong. Then they come back.

The board

The trailing C is not a revision. Waveshare sells a plain 1.75 as well and it is a different board — this firmware is for the 1.75C and will not run on the other one.

Two of those rows are load-bearing here.

• 32 MB of flash. The partition table assumes it, and most of it is the recording area. On a 16 MB board the table does not fit, so a plain 1.75 will not take this build at all — it is not a matter of losing a feature.
• No RTC. The 1.75C has no clock chip, so cutting the power loses the time; that is the whole reason the badge goes to the network for it. I2C on the real board answers at 18 34 40 5A 6B and nothing at 0x51. The PCF85063 driver is still in port_esp.c — it probes, finds nothing, and says so.

The 1.75C itself is listed two ways, With Battery and Without Battery. Everything here was written and tested on the one with the cell fitted; that is where the day-per-charge figure, the battery gauge and the standby measurements come from. The firmware does not require it — the power management chip is on the board either way — but the battery-less one has not been tried here.

No cloud

WiFi comes up for one reason — setting the clock, and only once the clock has gone stale — plus the scan when you first pick a network on the badge itself. Nothing is uploaded, there is no account, no telemetry, and recordings leave the board only when you plug it in and ask.

Put it on a board

Two ways. Neither of them needs a toolchain unless you want one.

1 · From the browser

Plug the badge in with a USB-C data cable and open the web flasher. It wants Chrome or Edge — WebSerial is not in Safari or Firefox. If the Connect button never finds a port, it is usually the cable; failing that, hold BOOT, tap RESET, release BOOT.

2 · From source

You need ESP-IDF 5.5 and nothing else; every other dependency is fetched on the first build.

git clone https://github.com/curisama/The-Badge
cd The-Badge
cp main/secrets.example.h main/secrets.h   # optional, may stay empty
idf.py build
idf.py -p /dev/ttyACM0 flash               # COMx on Windows

tools/setup.sh does the same and works out which OS you are on. The first build pulls down roughly 20 MB of components and takes a while; after that it is quick. Per-OS notes are in docs/SETUP.md.

It runs on a PC too

The whole interface builds and runs as a desktop program, with a fake IMU and a fake battery, so the tilt games and the power screens work there as well. Most of this firmware was written that way.

python3 sim/build.py
PORT=8792 python3 sim/server.py   # then open http://localhost:8792

How it is put together

• port.h — the seam. Everything hardware-specific sits behind it; the board and the simulator each supply a half. A file outside port_esp.c touching hardware directly is a bug.
• main/apps/ — one file per app.
• tools/regress.sh — reads the sources, then drives the simulator for the faults no pattern can catch. Half a minute. Not a test suite so much as a list of scars.