Heltec WiFi Kit 32
ESP32 dev board with a 0.96" OLED, LiPo charger and micro-USB - the original WiFi Kit 32 (V1 / V2), superseded by the S3-based V3.
Heltec WiFi Kit 32 Pinout
36 pins · 2.54 mm pitch
| Pin | GPIO | Labels | Status | Capabilities | Notes |
|---|---|---|---|---|---|
| 1 | - | GND | ground | - | |
| 2 | - | 3V3 | power | - | |
| 3 | - | Vext | power | - | Vext: switched 3.3 V output (LOW on the Vext control pin = on) |
| 4 | - | RSTEN | control | - | |
| 5 | 13 | A14T4PWM | strapping | adc · touch | |
| 6 | 12 | A15T5PWM | strapping | adc · touch | |
| 7 | 14 | A16T6PWM | strapping | adc · touch | |
| 8 | 27 | A17T7PWM | safe | adc · touch | |
| 9 | 26 | A19DAC2PWM | safe | adc · dac | |
| 10 | 25 | LED_BUILTINA18DAC1LEDPWM | safe | adc · dac | |
| 11 | 33 | A5T8PWM | safe | adc · touch | |
| 12 | 32 | A4T9PWM | safe | adc · touch | |
| 13 | 35 | A7 | strapping | adc | |
| 14 | 34 | A6 | strapping | adc | |
| 15 | 39 | A3 | strapping | adc | |
| 16 | 38 | A2 | strapping | adc | |
| 17 | 37 | A1 | strapping | adc | |
| 18 | 36 | A0 | strapping | adc | |
| 19 | - | GND | ground | - | |
| 20 | - | 5V | power | - | |
| 21 | - | 3V3 | power | - | |
| 22 | - | Vext | power | - | Vext: switched 3.3 V output (LOW on the Vext control pin = on) |
| 23 | 1 | TXPWM | uart | uart | |
| 24 | 3 | RXPWM | uart | uart | |
| 25 | 15 | A13T3PWMOLED_SCL | strapping | adc · touch | |
| 26 | 2 | A12T2PWM | strapping | adc · touch | |
| 27 | 0 | KEY_BUILTINA11T1 | strapping | adc · touch | |
| 28 | 4 | A10T0PWMOLED_SDA | safe | adc · touch | |
| 29 | 16 | PWMOLED_RST | safe | - | |
| 30 | 17 | GPIO17 | uart | uart · pwm | On the header (V1 and V2 pinout PDFs); UART2 TX |
| 31 | 5 | SSPWM | strapping | spi | |
| 32 | 18 | SCKPWM | safe | spi | |
| 33 | 23 | MOSIPWM | safe | spi | |
| 34 | 19 | MISOPWM | safe | spi | |
| 35 | 22 | SCLPWM | safe | i2c | |
| 36 | 21 | SDAPWMVext_Ctrl | safe | i2c |
Start with these
10 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
18 pins · 13 things to knowA14GPIO13 JTAG clock pin (TCK); also ADC2 channel 4 / Touch4 input. JTAG
Used for JTAG debugging (TCK); avoid using as GPIO if JTAG is needed.
A15GPIO12 Bootstrapping pin; JTAG TDI; sets flash voltage (VDD_SDIO); also HSPIQ (flash data line). Strapping
Keep LOW during boot (internal PD); pulling HIGH at reset selects 1.8V flash mode, causing flash brownout if 3.3V flash is used.
A16GPIO14 JTAG mode select pin (TMS); also HSPI CLK and PWM-capable GPIO. JTAG
Used for JTAG debugging (TMS); driving it as GPIO may interfere with JTAG or produce spurious signals at boot.
A7GPIO35A3GPIO39A2GPIO38A1GPIO37 Input-only GPIOs with ADC1 channels - no output driver Other
Cannot be used as output; only suitable for input.
- A7Input-only GPIO (no output driver); ADC1 channel 7.
- A3Input-only GPIO (no output); ADC1 channel 3, Hall sensor VN.
- A2Input-only GPIO (no output); ADC1 channel 2.
- A1Input-only GPIO (no output); ADC1 channel 1.
A6GPIO34 Input-only GPIO (no output driver); ADC1 channel 6. Other
Cannot be used as output (no drive capability); only suitable for analog/digital input.
A0GPIO36 Input-only GPIO (no output); ADC1 channel 0, Hall sensor VP. Other
Cannot be used as output; only suitable for input (e.g., analog read).
TXGPIO1 Default UART0 TX pin for USB-serial programming and console. UART
Connected to on-board USB-UART for uploading and logs; drives serial output at boot, so using as GPIO can disrupt programming or console.
RXGPIO3 Default UART0 RX pin for USB-serial programming (console input). UART
Used for receiving data from USB-UART (programming); also pulled HIGH at boot for console communication, so using as GPIO can disrupt uploads.
A13GPIO15A10GPIO4PWMGPIO16 Used by the OLED onboard hardware
Wired to the OLED on this board. The pin is yours if you give that up, but nothing else can share it.
- A13
- A10
- PWM
A12GPIO2 Bootstrapping pin (must be low or floating at reset); internal pull-down. Strapping
If driven HIGH on reset (while IO0 is LOW), selects an unsupported SDIO boot mode, causing boot failure.
KEY_BUILTINGPIO0 Bootstrapping pin (enter bootloader when low); internal pull-up. Strapping
Must be HIGH during boot for normal startup; if held LOW on reset, forces flash programming mode.
SSGPIO5 Bootstrapping pin; internal pull-up; VSPI CS0 (default SPI chip-select); acts as FSPIWP (flash write-protect) on internal-flash variants. Strapping
Must be HIGH during boot; if pulled LOW at reset, alters SDIO slave timing and may prevent normal boot.
SDAGPIO21 Used by the Vext power switch (V2) onboard hardware
Wired to the Vext power switch (V2) on this board. The pin is yours if you give that up, but nothing else can share it.
Across 36 pins (2.54 mm pitch), the Heltec WiFi Kit 32 exposes 28 GPIO plus GND, 3V3, Vext and 5V for power.
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 GPIO1 and GPIO3 cover serial logging and flashing.
On the analog side there are 18 ADC-capable pins for sensors and battery monitoring, PWM on 1 pins, 10 capacitive-touch inputs and 2 true DAC outputs.
If you want zero surprises, A17, A19, LED_BUILTIN, A5 and 6 more are free of any such role - the safest first picks. 18 of the exposed pins carry boot-time or system duties on the ESP32 (A14, A15, A16 and 15 more).
Getting started
flash your first firmware in ~2 minutesBoard: ESP32 Dev Module Flash Size: 4MB (32Mb) Flash Mode: DIO Partition Scheme: Default 4MB with spiffs (1.2MB APP/1.5MB SPIFFS) Upload Speed: 921600
// toggle GPIO27 - wire an LED and resistor to it
void setup() {
pinMode(27, OUTPUT);
}
void loop() {
digitalWrite(27, HIGH); delay(500);
digitalWrite(27, LOW); delay(500);
}[env:heltec_wifi_kit_32]
platform = espressif32
board = esp32dev
framework = arduino
monitor_speed = 115200
upload_speed = 921600esp32dev - or type it after board =.esp32:
board: esp32dev
variant: esp32
framework:
type: esp-idf
# blink - GPIO27
output:
- platform: gpio
pin: 27
id: led_out
light:
- platform: binary
name: "LED"
output: led_outesp32dev (same ids as PlatformIO).esptool.py --chip esp32 --port /dev/ttyACM0 \
--baud 921600 write_flash 0x1000 firmware.bin--port = your /dev/tty* (macOS/Linux) or COMx (Windows).Downloads
Free for non-commercial use, credit espboards.dev · License
Board illustration
The bare Heltec WiFi Kit 32 board drawn to scale at 50.2 × 25.5 mm, with no pin labels on it. Made for slide decks, wiring diagrams and project write-ups where a photo is too busy. Take the scalable SVG for print or editing, the high-resolution PNG to drop straight in, or the transparent PNG when you need it with no background behind it.
Pinout diagram
Every pin on both sides of the board with its functions, drawn by ESPboards from the ESP32 Series Datasheet v5.3 - the same sheet shown at the top of this page. The PNG is a high-resolution image for screens, the SVG is vector so it stays sharp at any size, and the PDF is laid out to print on A4 or Letter.
Yours to use, share and adapt for non-commercial work, as long as you credit espboards.dev - the full terms and ready-made credit lines are here.
Specifications
ESP32 · 50.2 × 25.5 mm · vs other ESP32 chips →Dimensions
About this board
At its core is the ESP32 - a dual-core Xtensa with both Bluetooth Classic and BLE.
Onboard you'll find an OLED 0.96" 128x64 display, battery charging via SH1.25-2 and Reset/PRG buttons.
- 50.2 x 25.5 mm on Heltec's V2 dimension drawing (the same outline as the V3, so V3 cases fit); the spec table in the same datasheet says 51 x 25.5
- Revisions: V1 (2017, 4 MB flash), V2 (2019, 8 MB flash, Vext on GPIO21, battery sense on GPIO13), V2.1 (battery sense moved to GPIO37). Superseded by the WiFi Kit 32 (V3), ESP32-S3.
- Arduino's Heltec WiFi Kit 32 entry assumes the V1's 4 MB flash; a V2 has 8 MB
Resources
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