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Heltec WiFi Kit 32(V3)
An ESP32-S3 board with an integrated 0.96" OLED display, designed for compact, battery-powered IoT and wireless projects.
50.2 × 25.5 mm
ESP32-S3
MCU
240MHz
clock
8MB
flash
512KB
SRAM
27· 20 ADC
GPIO
BLE 5.0+ WiFi
radio
Pinout
27 pins · 2.54 mm pitch
| Pin | GPIO | Labels | Status | Capabilities | Notes |
|---|---|---|---|---|---|
| 1 | 0 | KEY_BUILTIN | strapping | - | |
| 2 | 1 | A0T1PWM | safe | adc · touch | |
| 3 | 2 | A1T2PWM | safe | adc · touch | |
| 4 | 3 | A2T3PWM | strapping | adc · touch | |
| 5 | 4 | A3T4PWM | safe | adc · touch | |
| 6 | 5 | A4T5PWM | safe | adc · touch | |
| 7 | 6 | A5T6PWM | safe | adc · touch | |
| 8 | 7 | A6T7PWM | safe | adc · touch | |
| 9 | 8 | SSA7T8PWM | safe | adc · touch · spi | |
| 10 | 9 | SCKA8T9PWM | strapping | adc · touch · spi | |
| 11 | 10 | MOSIA9T10PWM | strapping | adc · touch · spi | |
| 12 | 11 | MISOA10T11PWM | strapping | adc · touch · spi | |
| 13 | 12 | A11T12PWM | strapping | adc · touch | |
| 14 | 13 | A12T13PWM | strapping | adc · touch | |
| 15 | 14 | A13T14PWM | strapping | adc · touch | |
| 16 | 15 | A14PWM | safe | adc | |
| 17 | 16 | A15PWM | safe | adc | |
| 18 | 17 | A16SDA_OLEDPWM | safe | adc | |
| 19 | 18 | A17SCL_OLEDPWM | safe | adc | |
| 20 | 19 | A18PWM | uart | adc | |
| 21 | 20 | A19PWM | uart | adc | |
| 22 | 21 | SDARST_OLEDPWM | safe | i2c | |
| 23 | 22 | SCLPWM | safe | i2c | |
| 24 | 35 | LED_BUILTINLED | strapping | - | |
| 25 | 36 | Vext | strapping | - | |
| 26 | 43 | TX | strapping | uart | |
| 27 | 44 | RX | strapping | uart |
Start with these
13 pins with no boot or system involvementA0T1A1T2A3T4A4T5A5T6A6T7SSA7A14PWMA15PWMA16SDA_OLEDA17SCL_OLEDSDARST_OLEDSCLPWM
Freely 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 |
|---|---|---|---|
| KEY_BUILTIN | 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 |
| A2 | GPIO3 | Sampled at reset to select JTAG interface (USB Serial/JTAG controller vs. external pins). Improper use can disable external JTAG or alter debug interface. | Strapping |
| SCK | FSPIHD | IO MUX pin of the general-purpose SPI2 (FSPI) bus, not of the in-package flash - that sits on GPIO26-32. The datasheet lists it as a priority-2 pin ("can be freely used without restrictions"), so it is only taken if your board wires flash, an SD card or a display to FSPI. | Other |
| MOSI | FSPICS0 | IO MUX pin of the general-purpose SPI2 (FSPI) bus, not of the in-package flash - that sits on GPIO26-32. The datasheet lists it as a priority-2 pin ("can be freely used without restrictions"), so it is only taken if your board wires flash, an SD card or a display to FSPI. | Other |
| MISO | FSPID | IO MUX pin of the general-purpose SPI2 (FSPI) bus, not of the in-package flash - that sits on GPIO26-32. The datasheet lists it as a priority-2 pin ("can be freely used without restrictions"), so it is only taken if your board wires flash, an SD card or a display to FSPI. | Other |
| A11 | FSPICLK | IO MUX pin of the general-purpose SPI2 (FSPI) bus, not of the in-package flash - that sits on GPIO26-32. The datasheet lists it as a priority-2 pin ("can be freely used without restrictions"), so it is only taken if your board wires flash, an SD card or a display to FSPI. | Other |
| A12 | FSPIQ | IO MUX pin of the general-purpose SPI2 (FSPI) bus, not of the in-package flash - that sits on GPIO26-32. The datasheet lists it as a priority-2 pin ("can be freely used without restrictions"), so it is only taken if your board wires flash, an SD card or a display to FSPI. | Other |
| A13 | FSPIWP | IO MUX pin of the general-purpose SPI2 (FSPI) bus, not of the in-package flash - that sits on GPIO26-32. The datasheet lists it as a priority-2 pin ("can be freely used without restrictions"), so it is only taken if your board wires flash, an SD card or a display to FSPI. | Other |
| TX | U0TXD (GPIO43) | Used for bootloader output and UART console logs. If repurposed, you will lose the default serial output (and programming via UART0). | Other |
| RX | U0RXD (GPIO44) | Used for bootloader input (download mode via serial). If repurposed, you cannot use the default UART0 download mode for programming the chip. | Other |
Only if you know the tricks
wired to flash or USB - expect a fight| Pin | Label | What to know | Role |
|---|---|---|---|
| A18 | USB_D- | By default connected to the on-chip USB Serial/JTAG controller. Using it as general GPIO without reconfiguring IO MUX will interfere with USB functionality. | USB |
| A19 | USB_D+ | By default connected to the on-chip USB Serial/JTAG controller. Using it as general GPIO without reconfiguring IO MUX will interfere with USB functionality. | USB |
| LED_BUILTIN | SPIIO6 (GPIO35) | The datasheet keeps GPIO33-37 for "the higher 4 bits data line interface and DQS interface for the SPI0/1 interface in 8-line SPI mode", so octal-PSRAM modules (N16R8 and friends) consume it and do not break it out. On quad-PSRAM or PSRAM-less parts it is an ordinary GPIO - check which variant your module carries. | Flash |
| Vext | SPIIO7 (GPIO36) | The datasheet keeps GPIO33-37 for "the higher 4 bits data line interface and DQS interface for the SPI0/1 interface in 8-line SPI mode", so octal-PSRAM modules (N16R8 and friends) consume it and do not break it out. On quad-PSRAM or PSRAM-less parts it is an ordinary GPIO - check which variant your module carries. | Flash |
These are recommendations, not hard rules - with the right pull-ups, timing and boot-state awareness most pins can be made to work. When in doubt, start green.
Pinout notes The Heltec WiFi Kit 32(V3) pinout brings out 27 GPIO pins at a 2.54 mm pitch - every one of them usable in your project. For peripherals, I²C is mapped to SDA…
The Heltec WiFi Kit 32(V3) pinout brings out 27 GPIO pins at a 2.54 mm pitch - every one of them usable in your project.
For peripherals, I²C is mapped to SDA on GPIO21 and SCL on GPIO22; the SPI bus (MOSI, MISO, SCK, SS) is broken out in full; TX/RX on GPIO43 and GPIO44 cover serial logging and flashing.
On the analog side there are 20 ADC-capable pins for sensors and battery monitoring and 14 capacitive-touch inputs.
If you want zero surprises, A0, A1, A3, A4 and 9 more are free of any such role - the safest first picks. 10 of the exposed pins carry boot-time or system duties on the ESP32-S3 (KEY_BUILTIN, A2, SCK and 7 more).
Getting started
flash your first firmware in ~2 minutes1
Connect over USB
Uses a CP2102 bridge - install the CP210x driver if no port appears. Not detected? Hold BOOT while plugging in.
2
Match & flash
Set the Tools options shown, then click Upload.
3
Verify it runs
GPIO1 toggles - wire an LED and resistor to it, or change the pin to your board's own LED.
Set these in Tools · leave everything else at default
Arduino IDE 2.x - Tools Copy
Board: "ESP32S3 Dev Module"▸
Flash Size: "8MB (64Mb)"▸
Flash Mode: "DIO"▸
Partition Scheme: "8M with spiffs (3MB APP/1.5MB SPIFFS)" (default)▸
Upload Speed: "921600"▸
▸ every other Tools option - leave at default
Board: ESP32S3 Dev Module Flash Size: 8MB (64Mb) Flash Mode: DIO Partition Scheme: 8M with spiffs (3MB APP/1.5MB SPIFFS) Upload Speed: 921600
Find it: Tools ▸ Board ▸ ESP32 Arduino ▸ ESP32S3 Dev Module
// toggle GPIO1 - wire an LED and resistor to it
void setup() {
pinMode(1, OUTPUT);
}
void loop() {
digitalWrite(1, HIGH); delay(500);
digitalWrite(1, LOW); delay(500);
}board to selectesp32-s3-devkitc-1⧉ copy
[env:heltec_wifi_kit_32_V3]
platform = espressif32
board = esp32-s3-devkitc-1
framework = arduino
monitor_speed = 115200
upload_speed = 921600Find it: PlatformIO Home ▸ Boards, search
esp32-s3-devkitc-1 - or type it after board =.board to selectesp32-s3-devkitc-1⧉ copy
esp32:
board: esp32-s3-devkitc-1
variant: esp32s3
framework:
type: esp-idf
# blink - GPIO1
output:
- platform: gpio
pin: 1
id: led_out
light:
- platform: binary
name: "LED"
output: led_outFind it: search ESPHome's board list for
esp32-s3-devkitc-1 (same ids as PlatformIO).esptool doesn't pick board settings - a prebuilt .bin already has them baked in. This is just the raw flash command.
esptool.py --chip esp32s3 --port /dev/ttyACM0 \
--baud 921600 write_flash 0x0 firmware.bin--port = your /dev/tty* (macOS/Linux) or COMx (Windows).Build details: sketch space 3342336 B · data 327680 B · DIO
Specifications
ESP32-S3 · 50.2 × 25.5 mm · vs other ESP32 chips →Compute
MCU
ESP32-S3
Clock
240 MHz
SRAM · Flash
512 KB · 8MB
Radio
Wi-Fi
802.11 b/g/n
Bluetooth
5.0 LE
Antenna
PCB
I/O
GPIO · ADC
27 · 20
UART · I²C · SPI
3 · 2 · 2
PWM
8 channels
Power
USB
USB-C
Serial
CP2102
Boot address
0x0
Electrical
Input
5V USB · 3.7V LiPo
Consumption
115mA active · 10µA sleep
Regulator
-
Display
Screen
OLED · 0.96" · 128x64
Driver
SSD1306
Touch
No
Flashing
Upload · OTA
esptool_py · esp_ota
Flash · Boot mode
DIO · QIO
Sketch · Data
3.19 MB · 320 KB
50.2 × 25.5 mm · pin pitch 2.54 mm
The Heltec WiFi Kit 32(V3) uses esptool_py for firmware uploads, esp_ota for over-the-air (OTA) updates. Flash mode is DIO with QIO boot mode. The maximum sketch size is 3.19 MB with 320 KB available for data.
About this board
At its core is the ESP32-S3 - a dual-core Xtensa with vector extensions suited to AI workloads.
Expect to pay about $12.99 - less than the ~$29 most ESP32-S3 boards go for.
27 GPIO are broken out - more than most ESP32-S3 boards, so the pin budget is rarely the constraint.
Onboard you'll find an OLED 0.96" 128x64 display, battery charging via JST-SH 1.25mm and Reset/PRG buttons.
- Vext pin (GPIO36) switches the 3.3V rail to the OLED & external sensors (350mA max)
- Onboard Li-Po charger with battery-voltage sensing via ADC on GPIO1 (VBAT)
Where to buy
prices are typical street pricesHeltec WiFi Kit 32(V3)
$12.99per unit, typical
Resources
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