ESP32S3 Walter Module
Compact ESP32-S3 module with rich I/O and connectivity - great for advanced IoT, edge AI, and embedded integration.
Pinout
28 pins · 2.54 mm pitch
| Pin | GPIO | Labels | Status | Capabilities | Notes |
|---|---|---|---|---|---|
| 1 | - | RESETEN | safe | - | ESP32 reset with 10k pullup |
| 2 | - | IO44/RX0RXD0 | uart | uart | ESP32 UART0 Receive |
| 3 | - | IO43/TX0TXD0 | uart | uart | ESP32 UART0 Transmit |
| 4 | 0 | DFU/3V3 ENIO0 | strapping | - | DFU when low on boot and 3V3 output enable |
| 5 | 12 | IO12 | strapping | - | General purpose I/O |
| 6 | 11 | IO11 | strapping | - | General purpose I/O |
| 7 | 13 | IO13 | strapping | - | General purpose I/O |
| 8 | 38 | IO38 | strapping | - | General purpose I/O |
| 9 | 39 | IO39 | strapping | - | General purpose I/O |
| 10 | 40 | IO40 | strapping | - | General purpose I/O |
| 11 | 41 | IO41 | strapping | - | General purpose I/O |
| 12 | 42 | IO42 | strapping | - | General purpose I/O |
| 13 | 2 | IO2 | safe | - | General purpose I/O |
| 14 | 1 | IO1 | safe | - | General purpose I/O |
| 15 | 4 | IO4 | safe | - | General purpose I/O |
| 16 | 5 | IO5 | safe | - | General purpose I/O |
| 17 | 6 | IO6 | safe | - | General purpose I/O |
| 18 | 7 | IO7 | safe | - | General purpose I/O |
| 19 | 15 | IO15 | safe | - | General purpose I/O |
| 20 | 16 | IO16 | safe | - | General purpose I/O |
| 21 | 17 | IO17 | safe | - | General purpose I/O |
| 22 | 18 | IO18 | safe | - | General purpose I/O |
| 23 | 8 | IO8 | safe | - | General purpose I/O |
| 24 | 9 | IO9 | strapping | - | General purpose I/O |
| 25 | 10 | IO10 | strapping | - | General purpose I/O |
| 26 | - | 3V3 OUTN/A | safe | - | Switchable 3.3VDC output |
| 27 | - | GND | ground | - | GND connection |
| 28 | - | VINN/A | power | - | DC Power input port |
Start with these
11 pins with no boot or system involvementFreely assignable - no strapping, flash, USB or JTAG duties. Ideal first picks for buttons, sensors and LEDs.
Fine - with a little care
sampled at boot or shared with debug/serial| Pin | Label | What to know | Role |
|---|---|---|---|
| DFU/3V3 EN | GPIO0 | Must be pulled high (default) or low (to enter UART download mode) at reset. Using it for other functions can interfere with boot mode configuration. | Strapping |
| IO39 | MTCK (GPIO39) | Default JTAG debugging TCK pin. If JTAG is needed, this pin must be free; it may also be used internally for PSRAM chip select on certain modules, so avoid repurposing it. | Other |
| IO40 | MTDO (GPIO40) | Default JTAG TDO output for debugging. Using it as GPIO will interfere with JTAG debugging functionality. | Other |
| IO41 | MTDI (GPIO41) | Default JTAG TDI input for debugging. Should be reserved for JTAG or left unused if JTAG is to remain available. | Other |
| IO42 | MTMS (GPIO42) | Default JTAG TMS signal for debugging. Using this pin for other purposes will disable the JTAG interface (unless JTAG is rerouted to USB). | Other |
Only if you know the tricks
wired to flash or USB - expect a fight| Pin | Label | What to know | Role |
|---|---|---|---|
| IO12 | FSPICLK | Drives the flash (and PSRAM) clock. This critical signal must be reserved for memory and not used as general GPIO. | Flash |
| IO11 | FSPID | Used as a data line for flash (and in-package PSRAM). It should not be used as GPIO when the flash/PSRAM is in use. | Flash |
| IO13 | FSPIQ | Used as a data line for flash/PSRAM transfers. Not available for other uses when flash/PSRAM is connected. | Flash |
| IO38 | FSPIWP | On flash-equipped chips, this pin is tied to the flash’s WP# (or D3) line. It should be avoided for other use, as it’s needed for flash operations. | Flash |
| IO9 | FSPIHD | Connected to external flash (data/hold signal) on most modules. Not recommended for use as GPIO, since it must remain dedicated to flash communication. | Flash |
| IO10 | FSPICS0 | Used to select the external flash chip. It is required for flash access and cannot be repurposed without losing flash connectivity | Flash |
Pinout notes The ESP32S3 Walter Module breaks out 28 pins in total: 22 GPIO for your project, with GND and VIN handling power. 5 of the exposed pins carry boot-time or…
The ESP32S3 Walter Module breaks out 28 pins in total: 22 GPIO for your project, with GND and VIN handling power.
5 of the exposed pins carry boot-time or system duties on the ESP32-S3 (DFU/3V3 EN, IO39, IO40 and 2 more) - check the guidance above before wiring anything to them. IO2, IO1, IO4, IO5 and 7 more are free of any such role - the safest first picks.
Getting started
flash your first firmware in ~2 minutesBoard: ESP32S3 Dev Module USB CDC On Boot: Enabled Flash Size: 16MB (128Mb) Flash Mode: DIO PSRAM: QSPI PSRAM Partition Scheme: 16M Flash (3MB APP / 9.9MB FATFS) Upload Speed: 921600
// blink the onboard LED
void setup() {
pinMode(2, OUTPUT);
}
void loop() {
digitalWrite(2, HIGH); delay(500);
digitalWrite(2, LOW); delay(500);
}[env:esp32s3-walter]
platform = espressif32
board = esp32-s3-devkitc-1
framework = arduino
monitor_speed = 115200
upload_speed = 921600
board_build.arduino.memory_type = qio_qspi
build_flags = -DBOARD_HAS_PSRAMesp32-s3-devkitc-1 — or type it after board =.esp32:
board: esp32-s3-devkitc-1
variant: esp32s3
framework:
type: esp-idf
psram:
mode: quad
speed: 80MHz
# blink - GPIO2
output:
- platform: gpio
pin: 2
id: led_out
light:
- platform: binary
name: "LED"
output: led_outesp32-s3-devkitc-1 (same ids as PlatformIO).esptool.py --chip esp32s3 --port /dev/ttyACM0 \
--baud 921600 write_flash 0x0 firmware.bin--port = your /dev/tty* (macOS/Linux) or COMx (Windows).Specifications
ESP32-S3 · 55 × 24.8 mmAbout this board
Inside sits the ESP32-S3 - a dual-core Xtensa with vector extensions suited to AI workloads.
At $54.00 it's on the expensive side for an ESP32-S3 board - most land around $30.
Around the module: 2MB (QSPI) PSRAM, GPS, cellular connectivity (Sequans Monarch 2 GM02SP) and Reset buttons.
It flashes over native USB - no serial-converter driver needed, which isn't a given among ESP32-S3 boards.
Walter is a small, highly integrated IoT module built to tackle complex connectivity and processing needs. At its core is the ESP32-S3, a versatile system-on-chip (SoC) featuring a dual-core processor with hardware acceleration for machine learning, cryptography, and signal processing. It includes a range of peripherals, such as UART, SPI, I²C, and CAN, alongside built-in Wi-Fi b/g/n and Bluetooth 5, providing robust local networking and communication options.
What sets Walter apart is its inclusion of the Sequans GM02SP modem, offering LTE-M and NB-IoT 5G connectivity for low-power, wide-area communication, ideal for IoT applications. The modem also integrates a GNSS receiver, adding precise positioning capabilities for tasks like asset tracking, navigation, or geolocation.
- LTE: CAT M1/NB1/NB2 (GM02SP module)
- GPS: GPS, GNSS Constellation support (GM02SP module)
- Ultra low deep sleep current of 9.8µA
- Certified for CE, FCC, IC, UKCA, New-Zealand and Australia
- Nano-SIM card slot plus integrated eSIM
- u.FL/IPEX connectors for the LTE and GNSS antennas, on-board PCB antenna for Wi-Fi/BLE
- 22 debug/flash testpoints on the underside for the GM02SP and ESP32-S3
Where to buy
prices are typical street pricesResources
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