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Heltec WiFi LoRa 32(V2)
Improved LoRa ESP32 board with better power management - suited for off-grid and battery-powered systems.
50.2 × 25.5 mm
ESP32
MCU
240MHz
clock
8MB
flash
520KB
SRAM
24· 16 ADC
GPIO
BLE 4.2+ WiFi
radio
Pinout
24 pins · 2.54 mm pitch
| Pin | GPIO | Labels | Status | Capabilities | Notes |
|---|---|---|---|---|---|
| 1 | 0 | KEY_BUILTINA11T1 | strapping | adc · touch | |
| 2 | 1 | TXPWM | uart | uart | |
| 3 | 2 | A12T2PWM | strapping | adc · touch | |
| 4 | 3 | RXPWM | uart | uart | |
| 5 | 4 | A10T0SDA_OLEDPWM | strapping | adc · touch | |
| 6 | 5 | SCKPWM | strapping | spi | |
| 7 | 12 | A15T5PWM | strapping | adc · touch | |
| 8 | 13 | A14T4PWM | strapping | adc · touch | |
| 9 | 14 | A16T6RST_LoRaPWM | strapping | adc · touch | |
| 10 | 15 | A13T3SCL_OLEDPWM | strapping | adc · touch | |
| 11 | 16 | RST_OLEDPWM | strapping | - | |
| 12 | 18 | SSPWM | safe | spi | |
| 13 | 19 | MISOPWM | safe | spi | |
| 14 | 21 | SDAVextPWM | safe | i2c | |
| 15 | 22 | SCLPWM | safe | i2c | |
| 16 | 25 | LED_BUILTINA18DAC1LEDPWM | safe | adc · dac | |
| 17 | 26 | A19DAC2DIO0PWM | safe | adc · dac | |
| 18 | 27 | MOSIA17T7PWM | safe | adc · touch · spi | |
| 19 | 32 | A4T9PWM | safe | adc · touch | |
| 20 | 33 | A5T8PWM | safe | adc · touch | |
| 21 | 34 | A6DIO2 | strapping | adc | |
| 22 | 35 | A7DIO1 | strapping | adc | |
| 23 | 36 | A0 | strapping | adc | |
| 24 | 39 | A3 | strapping | adc |
Start with these
9 pins with no boot or system involvementSSPWMMISOPWMSDAVextSCLPWMLED_BUILTINA18A19DAC2MOSIA17A4T9A5T8
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 HIGH during boot for normal startup; if held LOW on reset, forces flash programming mode. | Strapping |
| A12 | GPIO2 | If driven HIGH on reset (while IO0 is LOW), selects an unsupported SDIO boot mode, causing boot failure. | Strapping |
| A10 | GPIO4 | Sampled at reset for boot config; should not be driven at boot (affects boot mode timing). | Strapping |
| SCK | GPIO5 | Must be HIGH during boot; if pulled LOW at reset, alters SDIO slave timing and may prevent normal boot. | Strapping |
| A15 | MTDI (GPIO12) | Keep LOW during boot (internal PD); pulling HIGH at reset selects 1.8V flash mode, causing flash brownout if 3.3V flash is used. | Strapping |
| A14 | MTCK (GPIO13) | Used for JTAG debugging (TCK); avoid using as GPIO if JTAG is needed. | Other |
| A16 | MTMS (GPIO14) | Used for JTAG debugging (TMS); driving it as GPIO may interfere with JTAG or produce spurious signals at boot. | Other |
| A13 | MTDO (GPIO15) | Keep HIGH during boot (internal PU); if LOW on reset, bootloader log is silenced and boot mode may change. | Strapping |
| A6 | GPIO34 | Cannot be used as output (no drive capability); only suitable for analog/digital input. | Other |
| A7 | GPIO35 | Cannot be used as output; only suitable for input. | Other |
| A0 | GPIO36 (SENSOR_VP) | Cannot be used as output; only suitable for input (e.g., analog read). | Other |
| A3 | GPIO39 (SENSOR_VN) | Cannot be used as output; only suitable for input. | Other |
Only if you know the tricks
wired to flash or USB - expect a fight| Pin | Label | What to know | Role |
|---|---|---|---|
| TX | U0TXD (GPIO1) | Connected to on-board USB-UART for uploading and logs; drives serial output at boot, so using as GPIO can disrupt programming or console. | USB |
| RX | U0RXD (GPIO3) | Used for receiving data from USB-UART (programming); also pulled HIGH at boot for console communication, so using as GPIO can disrupt uploads. | USB |
| RST_OLED | GPIO16 | Connected to internal PSRAM on PSRAM-enabled modules; not usable as GPIO on those modules. | 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 All 24 pins on the Heltec WiFi LoRa 32(V2) are usable GPIO, spaced at the standard 2.54 mm pitch. Peripheral wiring is straightforward: I²C is mapped to SDA on…
All 24 pins on the Heltec WiFi LoRa 32(V2) are usable GPIO, spaced at the standard 2.54 mm pitch.
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 16 ADC-capable pins for sensors and battery monitoring, 10 capacitive-touch inputs and 2 true DAC outputs.
12 of the exposed pins carry boot-time or system duties on the ESP32 (KEY_BUILTIN, A12, A10 and 9 more) - check the guidance above before wiring anything to them. SS, MISO, SDA, SCL and 5 more are free of any such role - the safest first picks.
Getting started
flash your first firmware in ~2 minutes1
Connect over USB
Serial chip: CP2102. Not detected? Hold BOOT while plugging in.
2
Flash with your tool
Arduino IDE, PlatformIO, ESPHome or esptool - copy the settings on the right.
3
Verify it runs
The blink example uses GPIO18 - swap for your board's LED pin if different.
Board: Heltec Wifi Lora 32 V2
Flash Size: 8MB · DIO
Upload Speed: 921600
// blink
pinMode(18, OUTPUT);
digitalWrite(18, LOW); // on (often inverted)[env:heltec_wifi_lora_32_V2]
platform = espressif32
board = esp32dev
framework = arduino
monitor_speed = 115200
upload_speed = 921600esp32:
board: esp32dev
variant: heltec_wifi_lora_32_V2
framework:
type: esp-idf
# blink - GPIO18
output:
- platform: gpio
pin: 18
id: led_out
light:
- platform: binary
name: "LED"
output: led_outesptool.py --chip esp32 --port /dev/ttyACM0 \
write_flash 0x0 firmware.binBuild details: sketch space 3342336 B · data 327680 B · DIO
Specifications
ESP32 · 50.2 × 25.5 mmCompute
MCU
ESP32
Clock
240 MHz
SRAM · Flash
520 KB · 8MB
Radio
Wi-Fi
802.11 b/g/n
Bluetooth
4.2 LE
Antenna
PCB
I/O
GPIO · ADC
24 · 16
UART · I²C · SPI
3 · 2 · 4
PWM
16 channels
Power
USB
Micro-USB
Serial
CP2102
Boot address
0x1000
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 LoRa 32(V2) 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
Inside sits the ESP32 - a dual-core Xtensa with both Bluetooth Classic and BLE.
The $17.90 price tag is typical for an ESP32 board.
Around the module: an OLED 0.96" 128x64 display, LoRa (SX1276), battery charging via JST-SH 1.25mm and Reset/PRG buttons.
- 2.4GHz metal spring antenna for Wi-Fi/BT; IPEX (u.FL) connector with external antenna for LoRa
- Onboard Li-Po charge/discharge management with automatic USB/battery power switching
- LoRa variants ship as SX1276 (868/915MHz) or SX1278 (433MHz)
Where to buy
prices are typical street pricesHeltec WiFi LoRa 32(V2)
$17.90per unit, typical
Resources
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