Heltec Wireless Stick Lite

by Heltec

Display-less ESP32-PICO-D4 + SX1276 LoRa stick with micro-USB - the original Wireless Stick Lite, superseded by the S3-based V3.

Micro-USB

Pinout Datasheet ↗

59.3 × 24.8 mm

ESP32

MCU

240MHz

clock

4MB

flash

520KB

SRAM

34· 18 ADC

GPIO

BLE 4.2+ WiFi

radio

Heltec Wireless Stick Lite Pinout

40 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 (V1 pinout PDF)
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	GPIO17Flash_SD0	strapping	pwm
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	8	GPIO8Flash_SD1	strapping	pwm
19	7	GPIO7Flash_SD3	strapping	pwm
20	6	GPIO6Flash_CLK	strapping	pwm
21	-	5V	power	-
22	-	3V3	power	-
23	-	GND	ground	-
24	16	GPIO16Flash_CS	strapping	pwm
25	4	A10T0PWM	safe	adc · touch
26	0	KEY_BUILTINA11T1	strapping	adc · touch
27	2	A12T2PWM	strapping	adc · touch
28	15	A13T3PWM	strapping	adc · touch
29	27	MOSIA17T7PWMLoRa_MOSI	safe	adc · touch · spi
30	32	A4T9PWM	safe	adc · touch
31	33	A5T8PWM	safe	adc · touch
32	13	A14T4PWM	strapping	adc · touch
33	12	A15T5PWM	strapping	adc · touch
34	-	RSTEN	control	-
35	14	A16T6PWMLoRa_RST	strapping	adc · touch
36	26	A19DAC2PWMLoRa_DIO0	safe	adc · dac
37	25	LED_BUILTINA18DAC1LEDPWM	safe	adc · dac
38	9	GPIO9U1_RXD	uart	uart · pwm	On the header (V1 pinout PDF): UART1 RX. Free on the PICO-D4, whose flash is internal
39	10	GPIO10U1_TXD	uart	uart · pwm	On the header (V1 pinout PDF): UART1 TX
40	11	GPIO11Flash_SD2	strapping	pwm

Download the Heltec Wireless Stick Lite pinout Free to use and share for non-commercial work, as long as you credit espboards.dev. License.

PNG - download the Heltec Wireless Stick Lite pinout, high resolution image 4800 px wide · 1.7 MB SVG - download the Heltec Wireless Stick Lite pinout as a vector file Vector, any size · 159 KB PDF - download the Heltec Wireless Stick Lite pinout as a printable PDF A4, print ready · 698 KB

34 GPIOs broken out 8 free · 12 need care · 14 to avoid

Start with these

8 pins with no boot or system involvement

SCLGPIO22GPIO23A10GPIO4A4GPIO32A5GPIO33LED_BUILTINGPIO25GPIO9GPIO10

Freely assignable - no strapping, flash, USB or JTAG duties. Ideal first picks for buttons, sensors and LEDs.

Fine - with a little care

12 pins · 10 things to know

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.

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.

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.

A13GPIO15 Bootstrapping pin; JTAG TDO; controls UART0 boot log output; also HSPICS0 (secondary SPI CS). Strapping

Keep HIGH during boot (internal PU); if LOW on reset, bootloader log is silenced and boot mode may change.

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

14 pins · 2 things to know

SSGPIO18A7GPIO35A6GPIO34SCKGPIO5MISOGPIO19MOSIGPIO27A16GPIO14A19GPIO26 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

GPIO17GPIO8GPIO7GPIO6GPIO16GPIO11 Used by the internal flash (ESP32-PICO-D4) onboard hardware

Wired to the internal flash (ESP32-PICO-D4) on this board, which is soldered down. Driving it from your own code breaks that function.

GPIO17
GPIO8
GPIO7
GPIO6
GPIO16
GPIO11

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.

The Heltec Wireless Stick Lite pinout brings out 40 pins at a 2.54 mm pitch - 34 usable GPIO alongside the Vext, GND, 5V and 3V3 power rails.

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 9 pins, 10 capacitive-touch inputs and 2 true DAC outputs.

If you want zero surprises, SCL, GPIO23, A10, A4 and 4 more are free of any such role - the safest first picks. 12 of the exposed pins carry boot-time or system duties on the ESP32 (RX, TX, SDA and 9 more).

Getting started

flash your first firmware in ~2 minutes

Tool:

Connect over USB

Uses a CP2102 bridge - install the CP210x driver if no port appears. Not detected? Hold BOOT while plugging in.

Match & flash

Set the Tools options shown, then click Upload.

Verify it runs

GPIO22 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: "ESP32 Dev Module"▸

Flash Size: "4MB (32Mb)"▸

Flash Mode: "DIO"▸

Partition Scheme: "Default 4MB with spiffs (1.2MB APP/1.5MB SPIFFS)" (default)▸

Upload Speed: "921600"▸

▸ every other Tools option - leave at default

Board: 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

Find it: Tools ▸ Board ▸ ESP32 Arduino ▸ ESP32 Dev Module

blink.ino Copy

// 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);
}

board to selectesp32dev⧉ copy

platformio.ini Copy

[env:heltec_wireless_stick_lite]
platform = espressif32
board = esp32dev
framework = arduino
monitor_speed = 115200
upload_speed = 921600

Find it: PlatformIO Home ▸ Boards, search esp32dev - or type it after board =.

board to selectesp32dev⧉ copy

device.yaml Copy

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_out

Find it: search ESPHome's board list for esp32dev (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.

terminal Copy

esptool.py --chip esp32 --port /dev/ttyACM0 \
  --baud 921600 write_flash 0x1000 firmware.bin

--port = your /dev/tty* (macOS/Linux) or COMx (Windows).

Build details: sketch space 1310720 B · data 327680 B · DIO

Downloads

Free for non-commercial use, credit espboards.dev · License

Board illustration

The bare Heltec Wireless Stick Lite 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.

SVG - download the Heltec Wireless Stick Lite board illustration as a vector file Vector, any size · 85 KB PNG - download the Heltec Wireless Stick Lite board image, high resolution 1200 px wide · 392 KB PNG transparent - download the Heltec Wireless Stick Lite board image with no background No background · 433 KB

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.

Free for non-commercial use, with the credit line kept.

Embed the Heltec Wireless Stick Lite pinout

Paste this where you want the diagram. Keep the credit line - it is what the licence asks for, and it is the only thing we want in return.

<figure>
  <img src="https://cdn.espboards.net/boards/heltec-wireless-stick-lite/diagram-1600.png"
       alt="Heltec Wireless Stick Lite pinout diagram" width="1600" loading="lazy">
  <figcaption>
    Heltec Wireless Stick Lite pinout by
    <a href="https://www.espboards.dev/esp32/heltec_wireless_stick_lite/">ESPboards</a>,
    <a href="https://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC 4.0</a>
  </figcaption>
</figure>

Using it commercially? Ask us first - it takes one email.

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 →

Compute

MCU

ESP32

Clock

240 MHz

SRAM · Flash

520 KB · 4MB

Radio

Wi-Fi

802.11 b/g/n

Bluetooth

4.2 LE

Antenna

3D + u.FL

I/O

GPIO · ADC

34 · 18

UART · I²C · SPI

3 · 2 · 2

PWM

16 channels

Power

USB

Micro-USB

Serial

CP2102

Boot address

0x1000

Electrical

Input

5V USB · 3.7V LiPo

Consumption

Regulator

Flashing

Upload · OTA

esptool_py · esp_ota

Flash · Boot mode

DIO · DIO

Sketch · Data

1.25 MB · 320 KB

Dimensions

59.3 × 24.8 mm · pin pitch 2.54 mm

The Heltec Wireless Stick Lite uses esptool_py for firmware uploads, esp_ota for over-the-air (OTA) updates. Flash mode is DIO with DIO boot mode. The maximum sketch size is 1.25 MB with 320 KB available for data.

About this board

At its core is the ESP32 - a dual-core Xtensa with both Bluetooth Classic and BLE.

34 GPIO are broken out - more than most ESP32 boards, so the pin budget is rarely the constraint.

Onboard you'll find LoRa (SX1276), battery charging via SH1.25-2 and Reset/PRG buttons.

ESP32-PICO-D4 system-in-package with 4 MB flash inside - GPIO16 / 17 are its internal flash lines, not pins
ProAnt metal chip antenna for Wi-Fi/BLE; IPEX (u.FL) socket for LoRa
Revisions: V1 (2017), V2.1 (2020, UPG2179 RF switch, TP4054 charger), V3 (2022, ESP32-S3 + SX1262, USB-C)

Resources

Board datasheet resource.heltec.cn↗ ESP32 datasheet espressif.com↗ Wireless Stick Lite (V3) - the successor espboards.dev↗Wireless Stick Lite hardware update log docs.heltec.org↗Wireless Stick Lite (V2) Datasheet (PDF) resource.heltec.cn↗

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