ESP32 HW-394 (WR-32)

Development Board

Code name: ESP32_HW_394 • Arduino Board: ESP32_DEV

ESP32 HW-394 (WR-32) is a development board based on the ESP32 microcontroller using XTENSA architecture.

This board features a maximum CPU frequency of 240 MHz and 4MB flash memory.

About ESP32 HW-394 (WR-32)

The ESP32 HW-394 (WR-32) is a compact development board based on the ESP32 WROOM-32 module, featuring integrated Wi-Fi 802.11 b/g/n and Bluetooth 4.2 + BLE for seamless wireless connectivity. 📶

With a dual-core Xtensa 32-bit LX6 processor running up to 240 MHz, 4MB flash memory, and 520KB SRAM, it's perfect for IoT projects, home automation, and embedded applications. ⚡

The board offers 34 GPIO pins with support for ADC (18 channels, 12-bit), DAC (2 channels), PWM, and various communication interfaces including UART, SPI, I2C, I2S, CAN, and Ethernet MAC. 🔌

Operating at 3.3V with ultra-low power consumption in deep sleep mode (as low as 10 µA), it's ideal for battery-powered devices. 🔋 Compact dimensions of 18mm x 25.5mm make it suitable for space-constrained designs. 📏

Where to Buy ESP32 HW-394 (WR-32)

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$5 per unit

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Technical Specifications

Complete technical specification details for ESP32 HW-394 (WR-32)

USB

Type Type-C

Serial Chip CH340

Connectivity

WiFi 802.11 b/g/n (2.4 GHz)

Bluetooth 4.2

BLE 4.2

Microcontroller

Model esp32

Clock Speed 240 MHz

Flash Size 4MB

Architecture xtensa

✨ Features & Pins

Digital IO 30

Analog Input 16

PWM 19

Interrupts 16

Quick Setup

Copy-paste configs for ESP32 HW-394 (WR-32) - auto‑generated from this board's exact hardware specs.

ESP32 240 MHz 4MB DIO Xtensa

In Arduino IDE 2 select Esp32 Hw 394 from the esp32 by Espressif package. In PlatformIO use board = esp32dev. ESP32 · 240 MHz · 4MB · DIO.

Tools menu settings

Board (select in Arduino IDE) Esp32 Hw 394

CPU Frequency 240 MHz

Flash Size 4MB

Flash Mode DIO

Upload Speed 921600

Architecture Xtensa

In Arduino IDE 2, open Boards Manager, search "esp32" by Espressif and install it. Then go to Tools → Board and select "Esp32 Hw 394" for the ESP32 HW-394 (WR-32).

platformio.ini


[env:esp32-hw-394]
platform  = espressif32
board     = esp32dev
framework = arduino

; Exact hardware config for ESP32 HW-394 (WR-32)
board_build.mcu        = esp32
board_build.f_cpu      = 240000000L
board_build.flash_size = 4MB
board_build.flash_mode = dio
board_upload.flash_size = 4MB

The board value is a close generic match - check PlatformIO board registry for an exact fit.

esp32: block (YAML)


esp32:
  board: esp32dev
  framework:
    type: arduino   # or "esp-idf"

# ESP32 HW-394 (WR-32) - 240 MHz ESP32
# Flash: 4MB | USB: Type-C

Paste into your device's .yaml. See ESPHome ESP32 docs for full options.

esptool.py - flash command


esptool.py \
  --chip esp32 \
  --baud 921600 \
  write_flash \
    --flash_mode dio \
    --flash_size 4MB \
    0x1000 bootloader.bin \
    0x8000    partitions.bin \
    0xe000    boot_app0.bin \
    0x10000   firmware.bin

Install: pip install esptool - replace firmware.bin with your binary - bootloader at 0x1000

ESP32 HW-394 (WR-32) Pinout Diagram

Complete pin reference for ESP32 HW-394 (WR-32)

The ESP32 HW-394 pinout is based on the ESP32 WROOM-32 module with 38 pins, providing extensive functionality in a compact form. Key power pins include 3V3 for 3.3V input and GND for ground connection, ensuring stable power for the module.

The pinout features dedicated communication pins such as TXD0 and RXD0 for UART0, and GPIO pins like IO0 to IO16 for general-purpose I/O. ADC channels (ADC1_CH0 and others) support 12-bit analog input for sensor readings, while DAC1 provides analog output capabilities.

Additional pins include EN for module enable and various GPIOs configurable for SPI, I2C, PWM, and more. This versatile pinout supports digital I/O, analog functions, and multiple protocols, making the ESP32 HW-394 suitable for diverse IoT and embedded projects.

Safe Pins to Use

These pins are safe for general GPIO usage without boot or system conflicts

IO18

IO19

IO21

IO22

IO23

IO25

IO26

IO27

IO32

IO33

Why Are These Pins Safe?

✓ No boot sequence involvement

✓ No flash/PSRAM connections

✓ No USB or JTAG conflicts

✓ Freely assignable without issues

Pins to Avoid or Use with Caution

Reserved for critical functions. Misuse may cause boot failures, programming issues, or system conflicts.

Strapping Pins

Boot behavior & flash voltage

JTAG Debugging

Low-level debugging interface

USB Pins

USB Serial/JTAG communication

Flash/SPI Pins

Memory & PSRAM connections

UART Serial

Debugging & firmware uploads

PIN	Label	Why Avoid	Type
IO0	GPIO0	Must be HIGH during boot for normal startup; if held LOW on reset, forces flash programming mode.	🛠️ Strapping
IO2	GPIO2	If driven HIGH on reset (while IO0 is LOW), selects an unsupported SDIO boot mode, causing boot failure.	🛠️ Strapping
IO4	GPIO4	Sampled at reset for boot config; should not be driven at boot (affects boot mode timing).	🛠️ Strapping
IO5	GPIO5	Must be HIGH during boot; if pulled LOW at reset, alters SDIO slave timing and may prevent normal boot.	🛠️ Strapping
IO12	MTDI (GPIO12)	Keep LOW during boot (internal PD); pulling HIGH at reset selects 1.8V flash mode, causing flash brownout if 3.3V flash is used.	🛠️ Strapping
IO13	MTCK (GPIO13)	Used for JTAG debugging (TCK); avoid using as GPIO if JTAG is needed.	🪛 Other
IO14	MTMS (GPIO14)	Used for JTAG debugging (TMS); driving it as GPIO may interfere with JTAG or produce spurious signals at boot.	🪛 Other
IO15	MTDO (GPIO15)	Keep HIGH during boot (internal PU); if LOW on reset, bootloader log is silenced and boot mode may change.	🛠️ Strapping
IO16	GPIO16	Connected to internal PSRAM on PSRAM-enabled modules; not usable as GPIO on those modules.	⚡ Flash
IO17	GPIO17	Connected to internal PSRAM on PSRAM-enabled modules; not usable as GPIO on those modules.	⚡ Flash
IO34	GPIO34	Cannot be used as output (no drive capability); only suitable for analog/digital input.	🪛 Other
IO35	GPIO35	Cannot be used as output; only suitable for input.	🪛 Other

ESP32 HW-394 (WR-32) Additional Information

More details about ESP32 HW-394 (WR-32)

ESP32 HW-394 Variants

🔌 Different Models

Flash Memory: Typically 4MB, but check specifications as some variants might differ.
Board Layout: Slight differences in component placement or additional features like onboard LEDs.

⚙️ Compatibility Notes

All variants are based on the ESP32 WROOM-32 module and should be compatible with standard ESP32 development tools. Always verify the pinout and specifications for your specific board version.

💡 Choosing the Right Variant

Look for boards with reliable USB chips and sufficient flash memory for your project needs. The HW-394 is a cost-effective option for ESP32 prototyping.

Useful Links

Datasheets and resources for ESP32 HW-394 (WR-32)

ESP32 Datasheet

Microcontroller reference

ESP32 HW-394 (WR-32) Custom Pin Mapping

Pin configuration and GPIO mapping for ESP32 HW-394 (WR-32)

Digital I/O Pins

Interrupt Pins

Analog Inputs

PWM Pins

Pin	Function	ESP Pin	I/O Type	Description
6	IO0	GPIO0	BIDIRECTIONAL	GPIO0, Boot Mode Selection
7	IO2	GPIO2	BIDIRECTIONAL	GPIO2, General Purpose I/O
8	IO4	GPIO4	BIDIRECTIONAL	GPIO4, General Purpose I/O
9	IO5	GPIO5	BIDIRECTIONAL	GPIO5, General Purpose I/O
10	IO12	GPIO12	BIDIRECTIONAL	GPIO12, ADC or GPIO
11	IO13	GPIO13	BIDIRECTIONAL	GPIO13, ADC or GPIO
12	IO14	GPIO14	BIDIRECTIONAL	GPIO14, ADC or GPIO
13	IO15	GPIO15	BIDIRECTIONAL	GPIO15, ADC or GPIO
14	IO16	GPIO16	BIDIRECTIONAL	GPIO16, General Purpose I/O
15	RX	GPIO3	INPUT	UART0 Receive
16	TX	GPIO1	OUTPUT	UART0 Transmit
17	IO17	GPIO17	BIDIRECTIONAL	GPIO17, General Purpose I/O
18	IO18	GPIO18	BIDIRECTIONAL	GPIO18, General Purpose I/O
19	IO19	GPIO19	BIDIRECTIONAL	GPIO19, General Purpose I/O
20	IO21	GPIO21	BIDIRECTIONAL	GPIO21, I2C SDA
21	IO22	GPIO22	BIDIRECTIONAL	GPIO22, I2C SCL
22	IO23	GPIO23	BIDIRECTIONAL	GPIO23, SPI MOSI
23	IO25	GPIO25	BIDIRECTIONAL	GPIO25, DAC1
24	IO26	GPIO26	BIDIRECTIONAL	GPIO26, DAC2
25	IO27	GPIO27	BIDIRECTIONAL	GPIO27, ADC
26	IO32	GPIO32	BIDIRECTIONAL	GPIO32, ADC
27	IO33	GPIO33	BIDIRECTIONAL	GPIO33, ADC
28	IO34	GPIO34	INPUT	GPIO34, ADC Input Only
29	IO35	GPIO35	INPUT	GPIO35, ADC Input Only

Legend

Function Pin role

GPIO ESP32 pin

I/O Direction

# Pin number

Pin Mappings

Complete pinout and GPIO mapping for ESP32 HW-394 (WR-32)

Digital I/O Pins

Interrupt Pins

Analog Inputs

PWM Pins

Pin	Analog	Touch	PWM	Other
0		T1
1			PWM	TX
2	A12	T2	PWM
3			PWM	RX
4	A10	T0	PWM
5			PWM
12	A15	T5	PWM
13	A14	T4	PWM
14	A16	T6	PWM
15	A13	T3	PWM
16			PWM
17			PWM
18			PWM
19			PWM
21			PWM	SDA
22			PWM	SCL
23			PWM	MOSI
25	A18			DAC1
26	A19			DAC2
27	A17	T8	PWM
32	A4	T9	PWM
33	A5	T10	PWM
34	A6			INPUT
35	A7			INPUT

Legend

A0 Analog input

T0 Touch sensor

PWM PWM capable

RX/TX Serial pins

LED Built-in LED

# Pin number

Default Tools & Configuration

Build and upload settings for ESP32 HW-394 (WR-32)

Setting	Value
Bootloader tool	esptool_py
Uploader tool	esptool_py
Network uploader tool	esp_ota
Bootloader address	`0x1000`
Flash mode	dio
Boot mode	dio
Maximum upload size	1280 KB (1310720 bytes)
Maximum data size	320 KB (327680 bytes)