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ESP32-S3 Support

Joypad OS supports ESP32-S3 as a build target for the BT2USB app. The ESP32-S3 has both BLE and USB OTG, making it a compact standalone BLE-to-USB HID gamepad adapter.

Overview

Feature Pico W / Pico 2 W ESP32-S3
Bluetooth Classic BT + BLE BLE only
USB Output USB Device (RP2040) USB OTG Device
Controllers All BT controllers BLE controllers only
Build System pico-sdk / CMake ESP-IDF / CMake
Firmware Update Drag-and-drop (.uf2) Drag-and-drop (.uf2) via TinyUF2

BLE-only limitation: ESP32-S3 only supports BLE controllers. Classic Bluetooth controllers (like DualShock 3 in BT mode) will not work. Most modern controllers support BLE.

Supported Controllers (BLE)

Controller Status
Xbox One / Series (BLE mode) Supported
8BitDo controllers (BLE mode) Supported
Switch 2 Pro (BLE) Supported
Generic BLE HID gamepads Supported

Not Supported (Classic BT only)

Controller Why
DualShock 3 Classic BT only
DualShock 4 Classic BT only
DualSense Classic BT only
Switch Pro Classic BT only
Wii U Pro Classic BT only
Wiimote Classic BT only

These controllers pair over Classic BT and require the Pico W build.

Hardware

Tested Boards

Board Flash Status Notes
Seeed XIAO ESP32-S3 8MB Tested User LED on GPIO 21 (active low)
ESP32-S3-DevKitC Varies Should work Untested

Why ESP32-S3?

ESP32-S3 is the only ESP32 variant with both BLE and USB OTG:

Chip BLE USB OTG bt2usb?
ESP32 Yes (+ Classic) No No
ESP32-S2 No Yes No
ESP32-S3 Yes Yes Yes
ESP32-C3/C6/H2 Yes No No

Firmware Updates (TinyUF2)

The ESP32-S3 build uses Adafruit TinyUF2 as a bootloader, enabling the same drag-and-drop .uf2 firmware updates as RP2040 boards.

How It Works

TinyUF2 lives in a factory partition on flash. When activated, it presents a USB mass storage drive. Drop a .uf2 file on the drive and the firmware updates automatically.

8MB Flash Layout
────────────────────────────────────────
0x000000  Bootloader (TinyUF2's custom 2nd-stage)
0x008000  Partition table
0x009000  NVS (20KB)
0x00E000  OTA data (8KB) — tells bootloader which app to run
0x010000  ota_0 (2MB) — Joypad firmware lives here
0x210000  ota_1 (2MB) — unused
0x410000  factory (256KB) — TinyUF2 mass storage app
0x450000  ffat (3.7MB) — TinyUF2 virtual FAT filesystem

Normal boot: bootloader reads OTA data, boots ota_0 (Joypad app). TinyUF2 mode: bootloader boots factory partition (TinyUF2), USB drive appears. Recovery: if ota_0 is corrupted/empty, bootloader falls back to factory (TinyUF2) automatically.

First-Time Setup

Flash the official TinyUF2 release for your board once. This installs the bootloader, partition table, and TinyUF2:

  1. Download the TinyUF2 release for your board from Adafruit TinyUF2 releases
  2. For XIAO ESP32-S3: tinyuf2-seeed_xiao_esp32s3-X.XX.X.zip
  3. Extract the zip and flash combined.bin: 
    esptool.py --chip esp32s3 -b 921600 write_flash 0x0 combined.bin
  4. The device reboots into TinyUF2 — a USB drive named XIAOS3BOOT appears
  5. Drop a .uf2 firmware file onto the drive (or run make flash-uf2-bt2usb_esp32s3)

After this one-time setup, all future updates are drag-and-drop.

Entering TinyUF2 Mode

Three ways to enter TinyUF2 from a running app:

Method How
Double-tap reset Press the reset button twice within 500ms
CDC command Send BOOTSEL over the USB serial port
Recovery If the app is corrupted, TinyUF2 boots automatically

Updating Firmware

Drag-and-drop (recommended for end users):

  1. Enter TinyUF2 mode (double-tap reset or send BOOTSEL)
  2. A USB drive appears (XIAOS3BOOT on XIAO)
  3. Copy the .uf2 file to the drive
  4. Device reboots into the new firmware

Via make (recommended for development):

# Build + flash via TinyUF2 USB drive (device must be in TinyUF2 mode)
make flash-uf2-bt2usb_esp32s3

# Build + flash via esptool USB serial (device must be in download mode)
make flash-bt2usb_esp32s3

Generating .uf2 files:

make uf2-bt2usb_esp32s3
# Output: releases/joypad_<version>_bt2usb_esp32s3.uf2

Build & Flash

Prerequisites

# One-time setup: install ESP-IDF and tools
make init-esp

This clones ESP-IDF v6.0 to ~/esp-idf and installs the ESP32-S3 toolchain. If you already have ESP-IDF installed, it will skip the clone and just install tools.

Build Commands

From the repo root:

make bt2usb_esp32s3                 # Build
make uf2-bt2usb_esp32s3             # Build + generate .uf2
make flash-uf2-bt2usb_esp32s3       # Build + flash .uf2 via TinyUF2 drive
make flash-bt2usb_esp32s3           # Build + flash via esptool
make monitor-bt2usb_esp32s3         # UART serial monitor (Ctrl+] to exit)

Or from the esp/ directory:

cd esp
source env.sh                       # Activate ESP-IDF environment
make build                          # Build
make uf2                            # Build + generate .uf2
make flash                          # Build + flash via esptool
make monitor                        # UART serial monitor

Board Configurations

Board-specific sdkconfig overrides go in esp/sdkconfig.board.<name>:

echo 'CONFIG_SOME_OPTION=y' > esp/sdkconfig.board.myboard
cd esp && make BOARD=myboard build

Usage

Pairing

  1. Flash the firmware
  2. The adapter starts scanning for BLE devices automatically on boot
  3. Put your controller into BLE pairing mode
  4. Once paired, the controller reconnects automatically on subsequent use

Button Controls

Action Function
Click Start 60-second BLE scan
Double-click Cycle USB output mode
Triple-click Reset to default HID mode
Hold Disconnect all devices and clear bonds

Status LED

LED State Meaning
Blinking No device connected (scanning/idle)
Solid on Device connected

USB Output Modes

Double-click the button to cycle through output modes: XInput, DInput, Switch, PS3, PS4/PS5.

CDC Serial Commands

Connect to the USB serial port for device management:

Command Function
VERSION Show firmware version
DEVICE Show connected controller info
BOOTSEL Reboot into TinyUF2 mode
HELP List all commands

Architecture

Threading Model

ESP32-S3 uses FreeRTOS with two tasks:

Main Task                    BTstack Task
  USB device polling           BLE scanning/pairing
  LED status updates           HID report processing
  Button input                 Controller data -> router
  Storage persistence

BTstack runs in its own FreeRTOS task. All BLE operations (scanning, pairing, data) happen in that task. The main task handles USB output, LED, and button input.

Shared Code

The ESP32-S3 build compiles the same shared source files as the Pico W build:

  • Core services (router, players, profiles, hotkeys, storage, LEDs)
  • All USB device output modes (HID, XInput, PS3, PS4, Switch, etc.)
  • All BT HID drivers (vendor-specific and generic)
  • BTstack host integration
  • CDC serial command interface

Platform-specific code is abstracted through src/platform/platform.h.

ESP32-Specific Files

Location Purpose
esp/main/main.c FreeRTOS entry point
esp/main/flash_esp32.c NVS-based settings storage
esp/main/button_esp32.c GPIO button driver
esp/main/btstack_config.h BLE-only BTstack configuration
esp/main/tusb_config_esp32.h TinyUSB device configuration
esp/partitions_uf2.csv Partition table (matches TinyUF2 layout)
esp/tools/ota_data_ota0.bin Pre-built OTA data (boots ota_0)
esp/tools/uf2conv.py UF2 file conversion tool
src/platform/esp32/platform_esp32.c Platform HAL (time, reboot, double-tap reset)
src/bt/transport/bt_transport_esp32.c BLE transport layer