ESP32S3 Walter Module Development Board

Code name: ESP32S3_DEV

ESP32S3 Walter Module development board is based on esp32s3 microcontroller and uses xtensa architecture. This board has a maximum CPU frequency of 240 MHz and a flash size of 16MB.

⚡ Tech Specs 📌 Pinout 🔗 Useful Links 🗺️ Mappings 🛠️ Tools

About ESP32S3 Walter Module

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.

Technical Specifications

🛰️ Connectivity

WiFi 802.11 b/g/n (2.4 GHz)

Bluetooth 5.0

BLE 5.0

LTE: CAT M1/NB1/NB2

🧠 Microcontroller

Model esp32s3

Clock Speed 240 MHz

Flash Size 16MB

Architecture xtensa

✨ Features

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
24 digital IO pins
22 external interrupt pins
22 analog input pins
22 PWM pins

View Full Datasheet

ESP32S3 Walter Module Pinout

✅ Safe Pins to Use

For general GPIO usage, these are the safest and most flexible choices:

🔹 RESET

🔹 IO44/RX0

🔹 IO43/TX0

🔹 DFU/3V3 EN

🔹 IO2

🔹 IO1

🔹 IO4

🔹 IO5

🔹 IO6

🔹 IO7

🔹 IO15

🔹 IO16

🔹 IO17

🔹 IO18

🔹 IO8

🔹 3V3 OUT

🔹 VIN

Why Are These Pins Safe?

Not involved in bootstrapping → No impact on device boot mode or system startup
Not linked to flash memory or PSRAM → Won't interfere with storage or memory access
Not dedicated to USB or JTAG → Free for general use without affecting debugging
No special hardware connections → Freely assignable without internal conflicts

⚠️ Pins to Avoid or Use with Caution

Some pins are reserved for critical functions like bootstrapping, JTAG debugging, USB communication, and flash memory operations. Misusing these pins may lead to boot failures, programming issues, USB conflicts, or disruptions in flash storage.

Critical Pin Categories:

🛠️ Strapping Pins: Control boot behavior and flash voltage selection
🔗 JTAG Debugging Pins: Required for low-level debugging
🔌 USB Communication Pins: Used for USB Serial/JTAG communication
⚡ Flash Memory & SPI Pins: Connected to SPI flash memory and PSRAM
📡 UART Serial Communication Pins: Used for debugging and firmware uploads

PIN	Label	Reason	Function
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
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
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

ESP32S3 Walter Module Useful Links

🔗 Datasheet

https://www.quickspot.io/datasheet/walter_datasheet.pdf

🔗 ESP32S3 Datasheet

https://www.espressif.com/sites/default/files/documentation/esp32-s3_datasheet_en.pdf

ESP32S3 Walter Module Pin Mappings

This development board provides 24 digital IO pins, out of which 22 can be used as external interrupt pins , 22 as analog input pins and 22 pins have Pulse-Width Modulation (PWM) .

Pin	Function	ESP Pin	Input/Output	Description
1	RESET	EN	input	ESP32 reset with 10k pullup
2	IO44/RX0	RXD0	bidirectional	ESP32 UART0 Receive
3	IO43/TX0	TXD0	bidirectional	ESP32 UART0 Transmit
4	DFU/3V3 EN	IO0	bidirectional	DFU when low on boot and 3V3 output enable
5	IO12	IO12	bidirectional	General purpose I/O
6	IO11	IO11	bidirectional	General purpose I/O
7	IO13	IO13	bidirectional	General purpose I/O
8	IO38	IO38	bidirectional	General purpose I/O
9	IO39	IO39	bidirectional	General purpose I/O
10	IO40	IO40	bidirectional	General purpose I/O
11	IO41	IO41	bidirectional	General purpose I/O
12	IO42	IO42	bidirectional	General purpose I/O
13	IO2	IO2	bidirectional	General purpose I/O
14	IO1	IO1	bidirectional	General purpose I/O
15	IO4	IO4	bidirectional	General purpose I/O
16	IO5	IO5	bidirectional	General purpose I/O
17	IO6	IO6	bidirectional	General purpose I/O
18	IO7	IO7	bidirectional	General purpose I/O
19	IO15	IO15	bidirectional	General purpose I/O
20	IO16	IO16	bidirectional	General purpose I/O
21	IO17	IO17	bidirectional	General purpose I/O
22	IO18	IO18	bidirectional	General purpose I/O
23	IO8	IO8	bidirectional	General purpose I/O
24	IO9	IO9	bidirectional	General purpose I/O
25	IO10	IO10	bidirectional	General purpose I/O
26	3V3 OUT	N/A	power output	Switchable 3.3VDC output
27	GND	GND	power ground	GND connection
28	VIN	N/A	power input	DC Power input port

Function Pin Function

ESP Pin Pin on ESP32

I/O Input/Output Pin

Description Pin Description

Default Tools

Bootloader tool	esptool_py
Uploader tool	esptool_py
Network uploader tool	esp_ota
Bootloader address	0x0
Flash mode	dio
Boot mode	qio
PSRAM type	qspi

The ESP32S3 Walter Module development board by default uses esptool_py uploader tool, esp_ota network uploader tool for Over-the-air (OTA) uploads and esptool_py bootloader tool. The bootloader starts at address "0x0". Flash mode and boot mode for ESP32S3 Walter Module development board by default is dio and qio respectively. The board uses qspi PSRAM type.