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. See the Heltec WiFi LoRa (V2) pages [5] for more details.
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
Hardware
ESP32 Features
Dual core Xtensa microprocessor (LX6), running at 160 or 240MHz
520KB of SRAM
802.11b/g/n/e/i
Bluetooth v4.2 BR/EDR and BLE
Various peripherals:
12-bit ADC with up to 18 channels
2x 8-bit DACs
10x touch sensors
4x SPI
2x I2S
2x I2C
3x UART
SD/SDIO/MMC host
Slave (SDIO/SPI)
Ethernet MAC
CAN bus 2.0
IR (RX/TX)
Motor PWM
LED PWM with up to 16 channels
Hall effect sensor
Temperature sensor
Cryptographic hardware acceleration (RNG, ECC, RSA, SHA-2, AES)
5uA deep sleep current
Asymmetric Multiprocessing (AMP)
ESP32 allows 2 different applications to be executed in ESP32 SoC. Due to its dual-core architecture, each core can be enabled to execute customized tasks in stand-alone mode and/or exchanging data over OpenAMP framework. See Inter-Processor Communication (IPC) folder as code reference.
For more information, check the ESP32 Datasheet [1] or the ESP32 Technical Reference Manual [2].
System Requirements
Binary Blobs
Espressif HAL requires RF 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.
Programming and Debugging
The heltec_wifi_lora32_v2 board supports the runners and associated west commands listed below.
| flash | debug | |
|---|---|---|
| esp32 | ✅ (default) |
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 built (and flashed) at least once.
There are two options to be used when building an application:
Sysbuild
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 <board> --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 built 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 <board> samples/hello_world
The usual flash target will work with the board configuration.
Here is an example for the Hello World
application.
# From the root of the zephyr repository
west build -b <board> 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! <board>
Board variants using Snippets
ESP32 boards can be assembled with different modules using multiple combinations of SPI flash sizes, PSRAM sizes and PSRAM modes.
The snippets under snippets/espressif provide a modular way to apply these variations at build time without duplicating board definitions.
The following snippet-based variants are supported:
Snippet name |
Description |
|---|---|
Flash memory size |
|
|
Board with 4MB of flash |
|
Board with 8MB of flash |
|
Board with 16MB of flash |
|
Board with 32MB of flash |
PSRAM memory size |
|
|
Board with 2MB of PSRAM |
|
Board with 4MB of PSRAM |
|
Board with 8MB of PSRAM |
PSRAM utilization |
|
|
Relocate flash to PSRAM |
|
Wi-Fi buffers in PSRAM |
To apply a board variant, use the -S flag with west build:
west build -b <board> -S flash-32M -S psram-4M samples/hello_world
Note
These snippets are applicable to boards with compatible hardware support for the selected flash/PSRAM configuration.
If no FLASH snippet is used, the board default flash size will be used.
If no PSRAM snippet is used, the board default psram size will be used.
Debugging
OpenOCD
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 for ESP32 [3].
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.
Further documentation can be obtained from the SoC vendor in JTAG debugging for ESP32 [4].
Here is an example for building the Hello World application.
# From the root of the zephyr repository
west build -b <board> 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 <board> 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