Heltec WiFi LoRa 32 (V2)

Overview

Heltec WiFi LoRa 32 is a classic IoT dev-board designed & produced by Heltec Automation(TM), it’s a highly integrated product based on ESP32 + SX127x, it has Wi-Fi, BLE, LoRa functions, also Li-Po battery management system, 0.96” OLED are also included. 1

The features include the following:

  • Microprocessor: ESP32 (dual-core 32-bit MCU + ULP core)

  • LoRa node chip SX1276/SX1278

  • Micro USB interface with a complete voltage regulator, ESD protection, short circuit protection, RF shielding, and other protection measures

  • Onboard SH1.25-2 battery interface, integrated lithium battery management system

  • Integrated WiFi, LoRa, Bluetooth three network connections, onboard Wi-Fi, Bluetooth dedicated 2.4GHz

    metal 3D antenna, reserved IPEX (U.FL) interface for LoRa use

  • Onboard 0.96-inch 128*64 dot matrix OLED display

  • Integrated CP2102 USB to serial port chip

System requirements

Prerequisites

The ESP32 toolchain xtensa-esp32-elf is required to build this port. The toolchain installation can be performed in two ways:

  1. Automatic installation

    west espressif install

    Note

    By default, the toolchain will be downloaded and installed under $HOME/.espressif directory (%USERPROFILE%/.espressif on Windows).

  2. Manual installation

    Follow the ESP32 Toolchain link to download proper OS package version. Unpack the toolchain file to a known location as it will be required for environment path configuration.

Build Environment Setup

Some variables must be exported into the environment prior to building this port. Find more information at Environment Variables on how to keep this settings saved in you environment.

Note

In case of manual toolchain installation, set ESPRESSIF_TOOLCHAIN_PATH accordingly. Otherwise, set toolchain path as below. If necessary, update the version folder path as in esp-2020r3-8.4.0.

On Linux and macOS:

export ZEPHYR_TOOLCHAIN_VARIANT="espressif"
export ESPRESSIF_TOOLCHAIN_PATH="${HOME}/.espressif/tools/zephyr"

On Windows:

# on CMD:
set ESPRESSIF_TOOLCHAIN_PATH=%USERPROFILE%\.espressif\tools\zephyr
set ZEPHYR_TOOLCHAIN_VARIANT=espressif

# on PowerShell
$env:ESPRESSIF_TOOLCHAIN_PATH="$env:USERPROFILE\.espressif\tools\zephyr"
$env:ZEPHYR_TOOLCHAIN_VARIANT="espressif"

Finally, retrieve required submodules to build this port. This might take a while for the first time:

west espressif update

Note

It is recommended running the command above after west update so that submodules also get updated.

Flashing

The usual flash target will work with the heltec_wifi_lora32_v2 board configuration. Here is an example for the Hello World application.

# From the root of the zephyr repository
west build -b heltec_wifi_lora32_v2 samples/hello_world
west flash

Refer to Building an Application and Run an Application for more details.

It’s impossible to determine which serial port the ESP32 board is connected to, as it uses a generic RS232-USB converter. The default of /dev/ttyUSB0 is provided as that’s often the assigned name on a Linux machine without any other such converters.

The baud rate of 921600bps is recommended. If experiencing issues when flashing, try halving the value a few times (460800, 230400, 115200, etc). It might be necessary to change the flash frequency or the flash mode; please refer to the esptool documentation for guidance on these settings.

All flashing options are now handled by the West (Zephyr’s meta-tool) tool, including flashing with custom options such as a different serial port. The west tool supports specific options for the ESP32 board, as listed here:

--esp-idf-path ESP_IDF_PATH

path to ESP-IDF

--esp-device ESP_DEVICE

serial port to flash, default $ESPTOOL_PORT if defined. If not, esptool will loop over available serial ports until it finds ESP32 device to flash.

--esp-baud-rate ESP_BAUD_RATE

serial baud rate, default 921600

--esp-flash-size ESP_FLASH_SIZE

flash size, default “detect”

--esp-flash-freq ESP_FLASH_FREQ

flash frequency, default “40m”

--esp-flash-mode ESP_FLASH_MODE

flash mode, default “dio”

--esp-tool ESP_TOOL

if given, complete path to espidf. default is to search for it in [ESP_IDF_PATH]/components/esptool_py/ esptool/esptool.py

--esp-flash-bootloader ESP_FLASH_BOOTLOADER

Bootloader image to flash

--esp-flash-partition_table ESP_FLASH_PARTITION_TABLE

Partition table to flash

For example, to flash to /dev/ttyUSB2, use the following command after having build the application in the build directory:

west flash -d build/ --skip-rebuild --esp-device /dev/ttyUSB2