The flow3r badge firmware is composed of a number of parts:


The ESP-IDF is the SDK provided by Espressif for its ESP32 series of devices. This SDK is written in C and heavily based around FreeRTOS.


The lowest layer of our own code, the Board Support Package is the driver layer for interacting with the badge hardware. It’s implemented as a standard ESP-IDF components, so you can use it in your own ESP-IDF based projects to quickly create fully custom experiences for the badge.


Micropython is a interpreter for a subset of the Python programming language. It runs as a FreeRTOS task and provides the main runtime for flow3r-specific code, including user (your own!) applications. This is the main subsystem you’ll be interacting with when developing applications.


st3m (pronounced: stem) is the main framework and standard library for code running on the badge. Its implementation is split into a C part (another ESP-IDF component, sometimes call C-st3m) and Micropython code (which lives in /flash/sys on the badge and in /python_payload in the repository, somtimes called Py-st3m).


The Recovery Mode firmware is a smaller version of the default firmware, and doesn’t contain an audio stack or a Python interpreter. It provides enough functionality to allow you to recover from bricks, or to update your firmware.


The badge has a single UNIX-like filesystem. This filesystem is visible to both C and Micropython software:





FAT32 with WL [1]

10MiB partition on internal Flash. Contains st3m Python code in sys/.



External SD card, if available.

SPI Flash Partitions

This is the SPI flash partition layout we use:






Bootloader (bootloader.bin).



Non-Volatile Storage.



Unused PHY data partition.



Recovery firmare (recovery.bin).



Main badge firmware (flow3r.bin).



FAT32 filesystem (with [1] layer).

Accessing files from a PC

If the badge is running correctly, you can access the filesystem over the micropython REPL, using tools like mpremote.

$ mpremote
MicroPython c48f94151-dirty on 1980-01-01; flow3r with ESP32S3
Type "help()" for more information.
>>> import os
>>> os.listdir('/')
>>> os.listdir('/flash/sys')
['', 'st3m', '.sys-installed']

$ mpremote ls :flash/sys
ls :flash/sys
           0 st3m
           0 .sys-installed


Your flow3r is not showing up using Linux?

To let mpremote to work properly your user needs to have access rights to ttyACM.

Quick fix: sudo chmod a+rw /dev/ttyACM[Your Device Id here]`

More sustainable fix: Setup an udev rule to automatically allow the logged in user to access ttyUSB

  1. To use this, add the following to /etc/udev/rules.d/60-extra-acl.rules: KERNEL=="ttyACM[0-9]*", TAG+="udev-acl", TAG+="uaccess"

  2. Reload udevadm control --reload-rules && udevadm trigger

You can also put the badge into Disk Mode to make it appear as a USB pendrive on your PC. However, only one of the two FAT32 block devices (internal flash partition or SD card) can be mounted at once.


The badge boot process is the following:

  1. The ESP32S3 ROM starts. If the BOOT0 (the left shoulder button) is pressed down, it will boot into serial mode, from which can be used to flash the firmware.

  2. The ESP32S3 ROM loads and executes the second stage bootloader from SPI Flash. The bootloader is currently a stock ESP-IDF bootloader, but this will likely change.

  3. The bootloader loads the partition table definition from SPI flash, loads and runs the factory partition from SPI flash.

  4. The badge firmware starts and the display shows ‘Starting…’

  5. The badge firmware initializes (ie. formats) the FAT32 filesystem on the internal flash if necessary. The filesystem is then mounted on /flash.

  6. The badge firmware checks if the badge has a /flash/sys/.sys-installed file. If not, st3m Micropython files are extracted there.

  7. The badge starts Micropython which then loads /flash/sys/

When Things Break

If you brick your badge by corrupting or messing up the files on the internal flash partition, you can always recover by somehow getting the badge into disk mode, mounting the internal flash partition and then removing all files and directories. Then, unmount the badge. After rebooting, the system partition will be restored to a stock state by the badge firmware.

Disk Mode can be started from the main firmware, either from the menu or by pressing buttons as indicated in various crash screens.

If the above is not possible, you can also start a limited Disk Mode from the Recovery Mode. The Recovery Mode can also be used to reflash the badge firmware partition in case it got corrupted.

However, if something’s really broken, you will have to perform a low-level flash via the ESP32 BootROM - see below.

Recovery Mode

Recovery Mode is a special mode in which the badge can get started which can help you perform simple fixes and update your firmware.

To start Recovery Mode:

  1. Make sure the badge has a power source: either a charged battery or USB power.

  2. Turn off the badge by sliding the power switch to the left.

  3. Start holding down the right trigger / shoulder button.

  4. Turn on the badge by sliding the power switch to the right.

You should be greeted with a purple screen from which multiple actions can be selected:

  1. Reboot: reboots the badge back into the current (non-recovery) firmware.

  2. Disk Mode: mounts the internal SPI flash FAT partition as a USB mass storage. This is effectively a copy of the Disk Mode from the main firmware.

  3. Format FAT partition: fully wipes the internal SPI flash, which should let you recover from most cases of bricking. On next reboot, the badge will re-populate the FAT partition with st3m files and should start up normally.

  4. Update firmware: flashes a file from the FAT partition onto the main firmware partition. This can be used to update your badge to the newest firmware or to an alternative firmware.

Flashing (low-level)

To perform a low-level flash which will reset the entire badge state to a known state, you have to first put it into bootrom mode by starting it up with the left shoulder button held. The badge screen will stay off, but when connected over USB it should show up as an Espressif USB/JTAG bridge.

Compared to recovery modes above, this options requires the use of specialized software:, available from most Linux distribution package managers.

Instructions on how to run are given with every firmware update release tarball.

Updating Firmware

(Moved to its own section)


Releases follow semantic versioning rules and are names v[major].[minor].[patch]..

Release candidates are suffixed with +rc[number], with v1.2.3+rc23 being the 23rd release candidate for version 1.2.3 (ie., if the RC is promoted to a build, it will become version 1.2.3).

Development versions (not tagged with a release or release candidate tag) are suffixed with -dev[num], where num is the number of commits from the beginning of the main branch history.

Builds from the main branch are currently always at version 0.