Heltec WiFi LoRa 32 (V1)
The original WiFi LoRa 32 (V1) - ESP32 + SX1276/78 LoRa with a 0.96" OLED and micro-USB, superseded by the V2 and the S3-based V3.
Heltec WiFi LoRa 32 (V1) Pinout
36 pins · 2.54 mm pitch
| Pin | GPIO | Labels | Status | Capabilities | Notes |
|---|---|---|---|---|---|
| 1 | - | GND | ground | - | |
| 2 | - | 5V | power | - | |
| 3 | - | 3V3 | power | - | |
| 4 | - | GND | ground | - | |
| 5 | 3 | RXPWM | uart | uart | |
| 6 | 1 | TXPWM | uart | uart | |
| 7 | - | RSTEN | control | - | |
| 8 | 0 | KEY_BUILTINA11T1 | strapping | adc · touch | |
| 9 | 22 | SCLPWM | safe | i2c | |
| 10 | 19 | MISOPWMLoRa_MISO | safe | spi | |
| 11 | 23 | GPIO23 | safe | pwm | On the header (V1 pinout PDF) |
| 12 | 18 | SSPWMLoRa_CS | safe | spi | |
| 13 | 5 | SCKPWMLoRa_SCK | strapping | spi | |
| 14 | 15 | A13T3PWMOLED_SCL | strapping | adc · touch | |
| 15 | 2 | A12T2PWM | strapping | adc · touch | |
| 16 | 4 | A10T0PWMOLED_SDA | safe | adc · touch | |
| 17 | 17 | GPIO17 | uart | uart · pwm | On the header (V1 pinout PDF) |
| 18 | 16 | PWMOLED_RST | safe | - | |
| 19 | - | GND | ground | - | |
| 20 | - | 5V | power | - | |
| 21 | - | 3V3 | power | - | |
| 22 | 36 | A0 | strapping | adc | |
| 23 | 37 | GPIO37A1 | strapping | adc | On the header (V1 pinout PDF); input-only |
| 24 | 38 | GPIO38A2 | strapping | adc | On the header (V1 pinout PDF); input-only |
| 25 | 39 | A3 | strapping | adc | |
| 26 | 34 | A6 | strapping | adc | |
| 27 | 35 | A7 | strapping | adc | |
| 28 | 32 | A4T9PWMLoRa_DIO2 | safe | adc · touch | |
| 29 | 33 | A5T8PWMLoRa_DIO1 | safe | adc · touch | |
| 30 | 25 | LED_BUILTINA18DAC1LEDPWM | safe | adc · dac | |
| 31 | 26 | A19DAC2PWMLoRa_DIO0 | safe | adc · dac | |
| 32 | 27 | MOSIA17T7PWMLoRa_MOSI | safe | adc · touch · spi | |
| 33 | 14 | A16T6PWMLoRa_RST | strapping | adc · touch | |
| 34 | 12 | A15T5PWM | strapping | adc · touch | |
| 35 | 13 | A14T4PWM | strapping | adc · touch | |
| 36 | 21 | SDAPWM | safe | i2c |
Start with these
5 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
15 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.
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.
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.
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).
GPIO37GPIO38A3GPIO39A7GPIO35 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.
- A7Input-only GPIO (no output driver); ADC1 channel 7.
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.
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.
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.
Only if you know the tricks
8 pins · 1 thing to knowMISOGPIO19SSGPIO18SCKGPIO5A4GPIO32A5GPIO33A19GPIO26MOSIGPIO27A16GPIO14 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.
- MISO
- SS
- SCK
- A4
- A5
- A19
- MOSI
- A16
The Heltec WiFi LoRa 32 (V1) pinout brings out 36 pins at a 2.54 mm pitch - 28 usable GPIO alongside the 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 2 pins, 10 capacitive-touch inputs and 2 true DAC outputs.
If you want zero surprises, SCL, GPIO23, GPIO17, LED_BUILTIN and 1 more are free of any such role - the safest first picks. 15 of the exposed pins carry boot-time or system duties on the ESP32 (RX, TX, KEY_BUILTIN and 12 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 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_wifi_lora_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 - 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 WiFi LoRa 32 (V1) 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, LoRa (SX1276), 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
- Wi-Fi/BLE via a printed PCB antenna (the V2 swapped it for a metal spring)
- V1 specifics: 4 MB flash, 26 MHz crystal, LoRa DIO1 / DIO2 on GPIO33 / GPIO32 (the V2 moved them to 35 / 34), no Vext switch
- Revisions: V1 (2017), V2 (2018, 8 MB flash, 40 MHz crystal, Vext), V2.1 (2019), V3 (2022, ESP32-S3 + SX1262). Heltec lists the V2 as phasing out in favour of the V3.
- LoRa uses an external antenna through an IPEX/u.FL connector
- Onboard LiPo charging with automatic USB/battery power switching
Resources
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