Heltec Wireless Stick
Slim ESP32 + SX1276 LoRa stick with a 0.49" OLED and micro-USB - the original Wireless Stick, superseded by the S3-based V3.
Heltec Wireless Stick Pinout
34 pins · 2.54 mm pitch
| Pin | GPIO | Labels | Status | Capabilities | Notes |
|---|---|---|---|---|---|
| 1 | - | Vext | power | - | Vext: switched 3.3 V output (LOW on the Vext control pin = on) |
| 2 | - | GND | ground | - | |
| 3 | 22 | SCLPWM | safe | i2c | |
| 4 | 3 | RXPWM | uart | uart | |
| 5 | 1 | TXPWM | uart | uart | |
| 6 | 21 | SDAPWMVext_Ctrl | safe | i2c | |
| 7 | 18 | SSPWMLoRa_CS | safe | spi | |
| 8 | 23 | GPIO23 | safe | pwm | On the header |
| 9 | 35 | A7LoRa_DIO1 | strapping | adc | |
| 10 | 34 | A6LoRa_DIO2 | strapping | adc | |
| 11 | 5 | SCKPWMLoRa_SCK | strapping | spi | |
| 12 | 19 | MISOPWMLoRa_MISO | safe | spi | |
| 13 | 17 | GPIO17 | uart | uart · pwm | On the header (Wireless Stick pinout and V2.1 datasheet) |
| 14 | 36 | A0 | strapping | adc | |
| 15 | 37 | GPIO37A1 | strapping | adc | On the header; input-only |
| 16 | 38 | GPIO38A2 | strapping | adc | On the header; input-only |
| 17 | 39 | A3 | strapping | adc | |
| 18 | - | 5V | power | - | |
| 19 | - | 3V3 | power | - | |
| 20 | - | GND | ground | - | |
| 21 | 16 | PWMOLED_RST | safe | - | |
| 22 | 4 | A10T0PWMOLED_SDA | safe | adc · touch | |
| 23 | 0 | KEY_BUILTINA11T1 | strapping | adc · touch | |
| 24 | 2 | A12T2PWM | strapping | adc · touch | |
| 25 | 15 | A13T3PWMOLED_SCL | strapping | adc · touch | |
| 26 | 27 | MOSIA17T7PWMLoRa_MOSI | safe | adc · touch · spi | |
| 27 | 32 | A4T9PWM | safe | adc · touch | |
| 28 | 33 | A5T8PWM | safe | adc · touch | |
| 29 | 13 | A14T4PWM | strapping | adc · touch | |
| 30 | 12 | A15T5PWM | strapping | adc · touch | |
| 31 | - | RSTEN | control | - | |
| 32 | 14 | A16T6PWMLoRa_RST | strapping | adc · touch | |
| 33 | 26 | A19DAC2PWMLoRa_DIO0 | safe | adc · dac | |
| 34 | 25 | LED_BUILTINA18DAC1LEDPWM | safe | adc · dac |
Start with these
6 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
14 pins · 10 things to knowRXGPIO3 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.
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.
SDAGPIO21 Used by the Vext power switch onboard hardware
Wired to the Vext power switch on this board. The pin is yours if you give that up, but nothing else can share it.
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).
GPIO37GPIO38A3GPIO39 Input-only GPIOs with ADC1 channels - no output driver Other
Cannot be used as output; only suitable for input.
- GPIO37Input-only GPIO (no output); ADC1 channel 1.
- GPIO38Input-only GPIO (no output); ADC1 channel 2.
- A3Input-only GPIO (no output); ADC1 channel 3, Hall sensor VN.
PWMGPIO16A10GPIO4A13GPIO15 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.
- PWM
- A10
- A13
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.
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.
A14GPIO13 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.
Only if you know the tricks
8 pins · 1 thing to knowSSGPIO18A7GPIO35A6GPIO34SCKGPIO5MISOGPIO19MOSIGPIO27A16GPIO14A19GPIO26 Used by the SX1276 LoRa radio onboard hardware
Wired to the SX1276 LoRa radio on this board, which is soldered down. Driving it from your own code breaks that function.
- SS
- A7
- A6
- SCK
- MISO
- MOSI
- A16
- A19
Across 34 pins (2.54 mm pitch), the Heltec Wireless Stick exposes 28 GPIO plus Vext, GND, 5V and 3V3 for power.
Peripheral wiring is straightforward: 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.
Beyond plain digital I/O you get 18 ADC-capable pins for sensors and battery monitoring, PWM on 2 pins, 10 capacitive-touch inputs and 2 true DAC outputs.
14 of the exposed pins carry boot-time or system duties on the ESP32 (RX, TX, SDA and 11 more) - check the guidance above before wiring anything to them. SCL, GPIO23, GPIO17, A4 and 2 more are free of any such role - the safest first picks.
Getting started
flash your first firmware in ~2 minutesBoard: ESP32 Dev Module Flash Size: 8MB (64Mb) Flash Mode: DIO Partition Scheme: 8M with spiffs (3MB APP/1.5MB SPIFFS) Upload Speed: 921600
// toggle GPIO22 - wire an LED and resistor to it
void setup() {
pinMode(22, OUTPUT);
}
void loop() {
digitalWrite(22, HIGH); delay(500);
digitalWrite(22, LOW); delay(500);
}[env:heltec_wireless_stick]
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 - GPIO22
output:
- platform: gpio
pin: 22
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 Wireless Stick board drawn to scale at 59.3 × 24.8 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 · 59.3 × 24.8 mm · vs other ESP32 chips →Dimensions
About this board
Inside sits the ESP32 - a dual-core Xtensa with both Bluetooth Classic and BLE.
Around the module: an OLED 0.49" 64x32 display, LoRa (SX1276), battery charging via SH1.25-2 and Reset/PRG buttons.
- ProAnt 440 metal chip antenna for Wi-Fi/BLE (V1)
- Revisions: V1 (2017), V2.1 (2020, UPG2179 RF switch, 40 MHz crystal), V3 (2022, ESP32-S3 + SX1262, USB-C). Heltec's V2.1 datasheet says 4 MB flash, its schematic and Arduino say 8 MB.
- IPEX (U.FL) connector for external LoRa antenna
- SX1276 LoRa, regional variants: 433 / 470-510 / 863-870 / 902-928 MHz
Resources
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