M5_NightscoutMon Web Flasher

Flash the Nightscout glucose monitor firmware straight from your browser — no software to install.

This browser can't flash devices. Web Serial is required — use Google Chrome or Microsoft Edge on a desktop computer (Windows, macOS or Linux). Firefox and Safari are not supported, and neither are phones or tablets.

Pick the entry that matches your device exactly. The flasher blocks ESP32 ↔ ESP32-S3 mix-ups automatically, but it cannot tell a 4 MB Basic from a 16 MB one, or a CoreS3 from a JC3248W535 — flashing the wrong one of those will not work. Connect only one device at a time via USB, then press its Install button and choose the serial port that appears.

M5Stack Basic 4 MB

Original grey M5Stack Basic bought 2020 or earlier (4 MB flash, no PSRAM).

Version: …

M5Stack Basic 16 MB / Fire / Core2

Basic v2.6/v2.7 (16 MB), all Fire models, and all Core2 models (incl. AWS and v1.1).

Version: …

M5Stack CoreS3

CoreS3 and CoreS3 SE (ESP32-S3).

Version: …

Guition JC3248W535 3.5″

Guition 3.5″ 320×480 ESP32-S3 display board (non-M5Stack).

Version: …

Before you start

Works in Chrome or Edge on any desktop OS — Windows, macOS, Linux or ChromeOS. Firefox and Safari lack Web Serial, and phones/tablets are not supported (on Android, use the app method from the wiki instead).
Use a USB data cable — many bundled cables are charge-only.
Drivers (Windows only — macOS and Linux have them built in): M5Stack Basic/Fire need the CP210x driver, Core2 needs the CH9102 driver. CoreS3 and the JC3248W535 use the chip's native USB and need no driver on any system.
If a CoreS3 or JC3248W535 doesn't show a serial port, hold its BOOT button while plugging in the USB cable, then try again (on the CoreS3 hold the reset button ~3 s until the green LED lights).
Choosing Erase device during install wipes saved settings — recommended for a first install, not needed for re-flashing.

After flashing

Configure the device following the setup wiki.
Later updates install over-the-air from the device's own web page — you only need this flasher once per device.