Flash Bruce firmware on the M5Stack Cardputer
Install the open-source Bruce firmware on your M5Stack Cardputer directly from this page — nothing to download or install. You need Chrome, Edge or Firefox 151+ on a desktop computer and a USB-C data cable.
Before you connect
Leave the SD card inserted — this page writes brucePins.conf to LittleFS and copies it to the card.
To have the computer see the Cardputer / Cardputer ADV serial port, set the side power switch to OFF, then plug USB-C. M5Stack's official Cardputer-Adv flash steps use the same switch-OFF position (the switch only cuts the battery; USB still powers the board). If the port still does not appear, hold G0, tap RESET or replug USB, then release G0.
🔍 Radio missing after flashing? Run the diagnostic first
If Bruce shows CC1101 not found or nRF24 not found on a Cardputer ADV with Hydra RF, check it before reflashing or replacing any board. The diagnostic reads the Bruce version, the LittleFS/SD brucePins.conf and both SPI radios in your browser — without flashing, writing or transmitting anything.
How do I flash Bruce on a Cardputer?
Set the side power switch to OFF, connect a USB-C data cable, click Connect, choose the serial port, then click Flash. The switch only cuts the battery; USB still powers the board. That is the official M5Stack Cardputer-Adv flash position. After the port appears, the ESP32-S3 enters download mode over USB — you do not hold BOOT for the write itself. If no port appears, hold G0, tap RESET or replug USB, then release G0.
Which browsers can flash the Cardputer?
| Browser | Supported |
|---|---|
| Chrome / Edge (desktop) | ✅ Yes |
| Chrome (Android) | ✅ Yes |
| Firefox 151+ (desktop) | ✅ Yes — first use adds a permission add-on |
| Safari (macOS / iOS) | ❌ No |
| Firefox (Android) | ❌ No |
Browser flashing relies on the Web Serial API: Chrome and Edge on desktop, Chrome on Android, and — since Firefox 151 for desktop (May 2026) — Firefox. Safari and every browser on iOS are out; see Web Serial is not supported.
Troubleshooting
| Symptom | Fix |
|---|---|
| No port shows in the picker / only appears after powering off | Set the side power switch to OFF, then plug USB-C. That is the official M5Stack Cardputer-Adv position (the switch cuts the battery only). Still missing? Hold G0, tap RESET or replug, release G0. See Cardputer download-mode sequence. |
| "Failed to connect" | Use Timed out waiting for packet header and re-enter Cardputer download mode. |
| Download / CORS error | The firmware host is briefly unreachable — wait and retry. |
| Wrong chip detected | Close any app holding the port; see Failed to open serial port. |
CC1101 not found, nRF24 not found, or "Module not found" | Run the read-only Hydra RF diagnostic first — it checks the Bruce version, device MAC, the LittleFS/SD brucePins.conf, both radio SPI branches and order stability without flashing or writing anything. If it reports a configuration problem, flash again with Automatically apply module config on to overwrite brucePins.conf on both LittleFS and the SD card. The Files menu shows the SD card; open LittleFS separately to see the internal copy. |
| Cardputer reboots unexpectedly (e.g. on RF Scan) | Re-flash the default version — it is always the current upstream release, and Bruce rewrote its RF stack in 1.16 (2026-07-24) to fix a class of RF reboots. If it still happens on the newest release, report it with your board and the exact menu at the Bruce issue tracker. |
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
Which Bruce version should I flash on the Cardputer / Cardputer ADV?
Flash the default. This page always offers the current upstream stable release — Bruce 1.16.1 today — and it is preselected for you; the list is refreshed from the Bruce project on every build, so you never have to look up a version number. Older releases are published at github.com/BruceDevices/firmware if you specifically need one. Every build we flash is a complete image, so you can move between releases at any time with a single flash.
What is Bruce firmware?
Bruce is an open-source multi-tool firmware for ESP32 devices, with Sub-GHz, RF, infrared, RFID/NFC, WiFi and BadUSB tools in one menu. It is community firmware (AGPL-3.0); this page flashes the upstream binary.
The computer does not see the Cardputer / Cardputer ADV. What should I do?
Set the side power switch to OFF, then plug USB-C. M5Stack's official Cardputer-Adv flash steps use that switch-OFF position — the switch only disconnects the battery; USB still powers the board. If the port still does not appear, hold G0, tap RESET or replug USB, then release G0. After the port appears, this page resets the ESP32-S3 into download mode over USB.
Does the Cardputer enter flash mode automatically?
After the serial port appears, yes. The ESP32-S3 USB-Serial-JTAG reset does not need BOOT held during the flash itself. Seeing the port first still needs the side switch OFF (and G0 if the port is missing).
Do I need an RF module for Bruce?
Bruce's Sub-GHz and 2.4 GHz tools need a CC1101 + nRF24 add-on such as the Hydra RF (Cardputer ADV) or Switchblade RF 3-in-1. Without a module the RF menus have no radio to drive.
Which browsers can flash the Cardputer?
Chrome or Edge on desktop, Chrome on Android, or Firefox 151+ on desktop. Flashing uses the Web Serial API; in Firefox the first connection also adds a permission add-on. Safari and every browser on iOS cannot flash.
WARNING
For educational and lawful testing purposes only. Comply with all applicable laws in your jurisdiction.