Flash Bruce firmware on the M5Stack CoreS3
Install the open-source Bruce firmware on your M5Stack CoreS3 (ESP32-S3) directly from this page. You need Chrome or Edge on a desktop computer and a USB-C data cable.
How do I flash Bruce on the CoreS3?
Connect the CoreS3 with a USB-C cable, click Connect, choose the serial port, then click Flash. The board resets into flash mode automatically — no buttons to hold.
Which browsers can flash the CoreS3?
| Browser | Supported |
|---|---|
| Chrome / Edge (desktop) | Yes |
| Chrome (Android) | Yes |
| Safari (macOS / iOS) | No |
| Firefox | No |
Browser flashing relies on the Web Serial API, available only in Chromium-based browsers.
Troubleshooting
| Symptom | Fix |
|---|---|
| No port shows in the picker | Use a USB-C data cable (not charge-only). Confirm the CoreS3 is powered on. |
| Failed to connect | Unplug and replug the device, then click Connect again. |
| Download / CORS error | The firmware host or proxy is briefly unreachable. Refresh and retry. |
| Board unresponsive after flash | Hold the BOOT button, press RST briefly while holding BOOT, release BOOT, then click Connect. |
What is Bruce?
Bruce is an open-source firmware tool for ESP32 devices used in wireless and hardware research and education. Source code and releases are published at github.com/BruceDevices/firmware under the AGPL-3.0 license.
Frequently asked questions
What is Bruce firmware?
Bruce is an open-source ESP32 multi-tool firmware (Sub-GHz, RF, IR, RFID/NFC, WiFi, BadUSB). It is community firmware (AGPL-3.0); this page flashes the upstream binary.
Does the M5Stack CoreS3 enter flash mode automatically?
Yes. The CoreS3 uses an ESP32-S3 with USB-Serial-JTAG, so the flasher resets it into the bootloader over USB automatically — just click Connect, no buttons needed.
Do I need an RF module for Bruce on the CoreS3?
Bruce's Sub-GHz tools need an external CC1101 module and the 2.4 GHz tools need an nRF24 module. The CoreS3 base unit does not include these radios, so you'll need add-on hardware to use those menus.
Which browsers can flash the CoreS3?
Chrome or Edge on desktop (and Chrome on Android). Flashing uses the Web Serial API, which Safari and Firefox do not support.
WARNING
For educational and lawful testing purposes only. Comply with all applicable laws in your jurisdiction.