Displays live blood glucose readings from a LibreLinkUp-connected Libre 2 sensor directly on a "Cheap Yellow Display" (CYD, ESP32-2432S028R) — no Home Assistant, no hub, no phone app required. The device talks straight to LibreLinkUp's API over WiFi.
This is v2: unlike v1, nothing is hardcoded into the source code. On first boot (or whenever you hold the BOOT button for a few seconds while it's already running), the device starts its own WiFi setup page where you enter your WiFi, LibreLinkUp login, and glucose thresholds — all saved to flash, so anyone can download this and configure it without touching a line of code.
- Everything from v1 (color-coded status bar, trend arrow, auto re-auth, stale-data fallback, follower-account support)
- Web-based setup portal (via WiFiManager) —
no code editing, no
secrets.hfile to fill in - Settings persist across power loss (ESP32's built-in flash storage)
- Hold the BOOT button for ~3 seconds any time while it's running (not during power-on — see note below) to reopen the setup page and change settings, with your current values pre-filled
- ESP32-2432S028R "CYD" board (this specific pin configuration is for a Sunton/JCZN
variant with an ILI9341 panel — see
platformio.iniif you have a different revision and need to adjust pins/driver)
- Install VS Code and the PlatformIO extension.
- Clone this repo and open the folder in VS Code — PlatformIO will detect the project automatically and install dependencies (TFT_eSPI, ArduinoJson, WiFiManager).
- Build and upload via PlatformIO (the arrow icon in the status bar). No config file to edit first — that all happens on the device itself next.
- On first boot, the CYD's screen shows a WiFi network name to join (e.g.
CYD-Glucose-Setup) and an address to visit (192.168.4.1). - On your phone or computer, join that WiFi network. A setup page should open automatically (or open that address manually).
- Pick your home WiFi, enter your LibreLinkUp email/password and your low/high glucose thresholds, and submit.
- The device reboots, connects to your WiFi, and starts showing glucose.
To reconfigure later: once the device has finished booting and is already running normally (showing glucose, or "No data yet..."), press and hold the BOOT button for about 3 seconds, then release. The setup page comes back up with your existing settings pre-filled.
Important: don't hold BOOT while plugging the device in. GPIO0 (BOOT) is a hardware "strapping pin" on the ESP32 — if it's held low at the exact instant of power-on, the chip's own boot ROM enters its flashing/download mode instead of running this firmware at all (you'd see a blank screen and no serial output). Always let it boot normally first, then hold BOOT to trigger reconfiguration.
This has been tested and confirmed working with LibreLinkUp follower accounts (a separate account that watches someone else's readings). There's also a fallback path intended for patient (self-monitoring) accounts, based on how the API is documented to behave, but it hasn't been verified against a real patient-role account — if you try it, consider opening an issue either way so this note can be updated.
This uses LibreLinkUp's unofficial, reverse-engineered API (the same one various
community projects and Home Assistant integrations rely on). Abbott has changed
required request headers before (e.g. an October 2025 update that changed the
expected version/product header values and added a mandatory Account-Id
header). If requests start failing after previously working, check
addLLUHeaders() in src/main.cpp first — that's almost certainly where an
update is needed.
MIT — see LICENSE.