Heltec WiFi LoRa 32 V2: specs and pinout
An ESP32 board with an on-board SX127x LoRa radio and a small OLED. This page covers the Heltec WiFi LoRa 32 (V2). The V3 (ESP32-S3 and SX1262) is a different board with a different pinout.
Specs
| Spec | Value | Source |
|---|---|---|
| Supply voltage (ESP32 chip) | 2.3 V / 3.0 V min, 3.3 V typ, 3.6 V max | source Table 5-2 (p.51) |
| Pin source / sink current (ESP32 chip) | 40 mA / 28 mA typ per pin at 3.3 V | source Table 5-3 (p.52) |
| LoRa transceiver frequency range (SX1276 chip level) | SX1276/77/78/79 family covers 137 MHz to 1020 MHz; the SX1276 part is 137-1020 MHz and the SX1278 part is 137-525 MHz (band fitted on this board is not stated) | source Cover page title; device comparison table (p.10) |
| LoRa transceiver sensitivity (SX1276 chip level) | down to -148 dBm | source Key product features (p.1) |
| LoRa transceiver max output (SX1276 chip level) | +20 dBm (100 mW) on PA_BOOST, limited to 1 % transmit duty cycle and a 2.4 V to 3.7 V supply at +20 dBm; up to +17 dBm is for continuous operation | source Key product features (p.1); Section 3.4.3 High Power +20 dBm Operation |
| LoRa transceiver supply (SX1276 chip level) | 1.8 V to 3.7 V up to +17 dBm output (2.4 V to 3.7 V at +20 dBm); operating -40 C to +85 C | source Section 2.3 Operating Range, Table 4 (p.13); Section 3.4.3 |
| ADC preamplifier GPIOs | 3.3 V tolerant only | source Notes box on the V2 pinout diagram |
| Pins that must hold a state while downloading | GPIO5 LOW, GPIO12 LOW, GPIO15 HIGH | source Tips box on the V2 pinout diagram |
Power
| Value | Source | |
|---|---|---|
| Supply | USB 5 V or the 5V pin; 3.3 V rail and a Vext 3.3 V output switched by a GPIO (LOW = on) | source SX1276 supply-current table (p.14); ESP32 Table 5-4 (p.52); Heltec V2 diagram notes |
| Current | SX1276 transmit 120 mA at +20 dBm on PA_BOOST, 87 mA at +17 dBm; ESP32 Wi-Fi TX 240 mA (802.11b) | source SX1276 supply-current table (p.14); ESP32 Table 5-4 (p.52); Heltec V2 diagram notes |
Pinout
Pin table is the Heltec WiFi LoRa 32 (V2) pinout diagram (SX127x LoRa plus OLED). The V3 has a different pinout; these rows apply to V2 only.
| Pin | Function | Voltage | Notes | Source |
|---|---|---|---|---|
| GND | GND | left header, position 1 from the top | source WIFI LoRa 32(V2) Pinout Diagram (single page) | |
| 5V | 5V | 5 V | left header, position 2 from the top | source WIFI LoRa 32(V2) Pinout Diagram (single page) |
| Vext | Vext (external 3.3 V output) | 3.3 V | left header, position 3 from the top; Switch through GPIO (LOW = on, HIGH = off) | source WIFI LoRa 32(V2) Pinout Diagram (single page) |
| Vext | Vext (external 3.3 V output) | 3.3 V | left header, position 4 from the top; Switch through GPIO (LOW = on, HIGH = off) | source WIFI LoRa 32(V2) Pinout Diagram (single page) |
| RX | GPIO3, U0_RXD | left header, position 5 from the top | source WIFI LoRa 32(V2) Pinout Diagram (single page) | |
| TX | GPIO1, U0_TXD | left header, position 6 from the top | source WIFI LoRa 32(V2) Pinout Diagram (single page) | |
| RST | RST | left header, position 7 from the top | source WIFI LoRa 32(V2) Pinout Diagram (single page) | |
| 0 | GPIO0, ADC2_1, Touch1, PRG button | left header, position 8 from the top; On-board PRG button | source WIFI LoRa 32(V2) Pinout Diagram (single page) | |
| 22 | GPIO22, SCL, V_SPI_WP, U0_RTS | left header, position 9 from the top | source WIFI LoRa 32(V2) Pinout Diagram (single page) | |
| 19 | GPIO19, LoRa_MISO, V_SPI_Q, U0_CTS | left header, position 10 from the top; Used by on-board LoRa radio | source WIFI LoRa 32(V2) Pinout Diagram (single page) | |
| 23 | GPIO23, V_SPI_D | left header, position 11 from the top | source WIFI LoRa 32(V2) Pinout Diagram (single page) | |
| 18 | GPIO18, LoRa_CS, V_SPI_CLK | left header, position 12 from the top; Used by on-board LoRa radio | source WIFI LoRa 32(V2) Pinout Diagram (single page) | |
| 5 | GPIO5, LoRa_SCK, V_SPI_CS0 | left header, position 13 from the top; Used by on-board LoRa radio; must be LOW when downloading | source WIFI LoRa 32(V2) Pinout Diagram (single page) | |
| 15 | GPIO15, OLED_SCL, Touch3, HSPI_CS0, ADC2_3 | left header, position 14 from the top; Used by on-board OLED; must be HIGH when downloading | source WIFI LoRa 32(V2) Pinout Diagram (single page) | |
| 2 | GPIO2, Touch2, HSPI_WP, ADC2_2 | left header, position 15 from the top | source WIFI LoRa 32(V2) Pinout Diagram (single page) | |
| 4 | GPIO4, OLED_SDA, Touch0, HSPI_HD, ADC2_0 | left header, position 16 from the top; Used by on-board OLED | source WIFI LoRa 32(V2) Pinout Diagram (single page) | |
| 17 | GPIO17, U2_TXD | left header, position 17 from the top | source WIFI LoRa 32(V2) Pinout Diagram (single page) | |
| 16 | GPIO16, OLED_RST, U2_RXD | left header, position 18 from the top; Used by on-board OLED | source WIFI LoRa 32(V2) Pinout Diagram (single page) | |
| GND | GND | right header, position 1 from the top | source WIFI LoRa 32(V2) Pinout Diagram (single page) | |
| 3V3 | 3V3 | 3.3 V | right header, position 2 from the top | source WIFI LoRa 32(V2) Pinout Diagram (single page) |
| 3V3 | 3V3 | 3.3 V | right header, position 3 from the top | source WIFI LoRa 32(V2) Pinout Diagram (single page) |
| 36 | GPI36, ADC1_0 | right header, position 4 from the top; Marked * (ADC preamplifier GPIO, 3.3 V tolerant only) | source WIFI LoRa 32(V2) Pinout Diagram (single page) | |
| 37 | GPI37, ADC1_1 | right header, position 5 from the top; Marked * (ADC preamplifier GPIO, 3.3 V tolerant only) | source WIFI LoRa 32(V2) Pinout Diagram (single page) | |
| 38 | GPI38, ADC1_2 | right header, position 6 from the top; Marked * (ADC preamplifier GPIO, 3.3 V tolerant only) | source WIFI LoRa 32(V2) Pinout Diagram (single page) | |
| 39 | GPI39, ADC1_3 | right header, position 7 from the top; Marked * (ADC preamplifier GPIO, 3.3 V tolerant only) | source WIFI LoRa 32(V2) Pinout Diagram (single page) | |
| 34 | GPI34, ADC1_6, LoRa DIO2 | right header, position 8 from the top; Marked *; LoRa radio line | source WIFI LoRa 32(V2) Pinout Diagram (single page) | |
| 35 | GPI35, ADC1_7, LoRa DIO1 | right header, position 9 from the top; Marked *; LoRa radio line | source WIFI LoRa 32(V2) Pinout Diagram (single page) | |
| 32 | XTAL32, GPIO32, ADC1_4, Touch9 | right header, position 10 from the top | source WIFI LoRa 32(V2) Pinout Diagram (single page) | |
| 33 | XTAL32, GPIO33, ADC1_5, Touch8 | right header, position 11 from the top | source WIFI LoRa 32(V2) Pinout Diagram (single page) | |
| 25 | GPIO25, ADC2_8, DAC2, LED | right header, position 12 from the top; On-board LED | source WIFI LoRa 32(V2) Pinout Diagram (single page) | |
| 26 | GPIO26, ADC2_9, DAC1, LoRa_DIO0 | right header, position 13 from the top; Used by on-board LoRa radio | source WIFI LoRa 32(V2) Pinout Diagram (single page) | |
| 27 | GPIO27, ADC2_7, TOUCH7, LoRa_MOSI | right header, position 14 from the top; Used by on-board LoRa radio | source WIFI LoRa 32(V2) Pinout Diagram (single page) | |
| 14 | GPIO14, ADC2_6, TOUCH6, LoRa_RST | right header, position 15 from the top; Used by on-board LoRa radio | source WIFI LoRa 32(V2) Pinout Diagram (single page) | |
| 12 | GPIO12, ADC2_5, TOUCH5 | right header, position 16 from the top; Must be LOW when downloading | source WIFI LoRa 32(V2) Pinout Diagram (single page) | |
| 13 | GPIO13, ADC2_4, TOUCH4 (printed TPUCH4) | right header, position 17 from the top | source WIFI LoRa 32(V2) Pinout Diagram (single page) | |
| 21 | GPIO21, SDA, V_SPI_HD, Vext control | right header, position 18 from the top; Vext control line | source WIFI LoRa 32(V2) Pinout Diagram (single page) |
Build with it
Project ideas for the Heltec WiFi LoRa 32 V2. Each link opens Soldr with the prompt filled in; Soldr assigns the pins, checks power and shows how to wire every part.
- LoRa temperature node: The radio is on board; use a LoRa band variant that is allowed where you live and add the matching antenna. A learning project.
- LoRa range tester: One board sends numbered packets and the other shows signal on the OLED; both must be the same band variant.
- LoRa weather sender: DHT22 data on a free GPIO that is not marked as used by the LoRa radio or OLED.
Common mistakes
- Pins marked with a red arrow are used by the on-board OLED and LoRa radio; do not reuse them (source: link, legend on the pinout diagram).
- GPIO5 and GPIO12 must be LOW and GPIO15 HIGH while downloading a program (source: link, Tips box).
- ADC preamplifier GPIOs (36 to 39, 34, 35) are 3.3 V tolerant only (source: link, Notes box).
Not covered by the official source
- Radio band (433, 868 or 915 MHz) and whether the radio is SX1276 or SX1278 is not stated on the pinout diagram.
- The maker's pinout diagram does not give supply and current limits for the board as a whole.