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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

Espressif HAL requires WiFi and Bluetooth binary blobs in order work. Run the command below to retrieve those files.

west blobs fetch hal_espressif

Note

It is recommended running the command above after west update.

Building & Flashing

Simple boot

The board could be loaded using the single binary image, without 2nd stage bootloader. It is the default option when building the application without additional configuration.

Note

Simple boot does not provide any security features nor OTA updates.

MCUboot bootloader

User may choose to use MCUboot bootloader instead. In that case the bootloader must be build (and flash) at least once.

There are two options to be used when building an application:

  1. Sysbuild

  2. Manual build

Note

User can select the MCUboot bootloader by adding the following line to the board default configuration file.

CONFIG_BOOTLOADER_MCUBOOT=y

Sysbuild

The sysbuild makes possible to build and flash all necessary images needed to bootstrap the board with the ESP32 SoC.

To build the sample application using sysbuild use the command:

west build -b heltec_wifi_lora32_v2 --sysbuild samples/hello_world

By default, the ESP32 sysbuild creates bootloader (MCUboot) and application images. But it can be configured to create other kind of images.

Build directory structure created by sysbuild is different from traditional Zephyr build. Output is structured by the domain subdirectories:

build/
├── hello_world
│   └── zephyr
│       ├── zephyr.elf
│       └── zephyr.bin
├── mcuboot
│    └── zephyr
│       ├── zephyr.elf
│       └── zephyr.bin
└── domains.yaml

Note

With --sysbuild option the bootloader will be re-build and re-flash every time the pristine build is used.

For more information about the system build please read the Sysbuild (System build) documentation.

Manual build

During the development cycle, it is intended to build & flash as quickly possible. For that reason, images can be build one at a time using traditional build.

The instructions following are relevant for both manual build and sysbuild. The only difference is the structure of the build directory.

Note

Remember that bootloader (MCUboot) needs to be flash at least once.

Build and flash applications as usual (see Building an Application and Run an Application for more details).

# From the root of the zephyr repository
west build -b heltec_wifi_lora32_v2/esp32/procpu samples/hello_world

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/esp32/procpu samples/hello_world
west flash

Open the serial monitor using the following command:

west espressif monitor

After the board has automatically reset and booted, you should see the following message in the monitor:

***** Booting Zephyr OS vx.x.x-xxx-gxxxxxxxxxxxx *****
Hello World! heltec_wifi_lora32_v2

Debugging

As with much custom hardware, the ESP32 modules require patches to OpenOCD that are not upstreamed yet. Espressif maintains their own fork of the project. The custom OpenOCD can be obtained at OpenOCD ESP32

The Zephyr SDK uses a bundled version of OpenOCD by default. You can overwrite that behavior by adding the -DOPENOCD=<path/to/bin/openocd> -DOPENOCD_DEFAULT_PATH=<path/to/openocd/share/openocd/scripts> parameter when building.

Here is an example for building the Hello World application.

# From the root of the zephyr repository
west build -b heltec_wifi_lora32_v2/esp32/procpu samples/hello_world -- -DOPENOCD=<path/to/bin/openocd> -DOPENOCD_DEFAULT_PATH=<path/to/openocd/share/openocd/scripts>
west flash

You can debug an application in the usual way. Here is an example for the Hello World application.

# From the root of the zephyr repository
west build -b heltec_wifi_lora32_v2/esp32/procpu samples/hello_world
west debug

Utilizing Hardware Features

Onboard OLED display

The onboard OLED display is of type ssd1306, has 128*64 pixels and is connected via I2C. It can therefore be used by enabling the SSD1306 128x64(/32) pixels generic shield as shown in the following for the LVGL basic sample sample:

# From the root of the zephyr repository
west build -b heltec_wifi_lora32_v2/esp32/procpu --shield ssd1306_128x64 samples/subsys/display/lvgl
west flash

References