Wemos Lolin32 Lite

Overview

WEMOS LOLIN32 Lite is a compact development board based on ESP32-D0WDQ6 or ESP32-D0WD-V3 chips. This board integrates complete Wi-Fi and Bluetooth Low Energy functions with a minimal footprint design. It features an onboard battery charging circuit and exposes selected GPIO pins on standard 2.54mm headers.

Hardware

This board uses the ESP32 chip with 4MB flash storage (W25Q32). A PH-2 battery connector with TP4054 charging IC enables portable applications. GPIO22 connects to an onboard LED. The board includes a CH340C USB-to-serial for programming. A RESET button allows manual resets. The board comes with either micro-USB or USB Type-C connector. For pin configuration, see the WEMOS LOLIN32 Lite Schematic [6].

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)

Boards featuring the ESP32 and ESP32-S3 SoC allows 2 different applications to be executed. 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.

Note

** AMP and serial output support **

In the current Zephyr ESP32 implementation, access to Zephyr-managed serial drivers (such as printk(), logging, or the console UART) is not yet implemented for applications running on the APPCPU. As a result, serial output APIs provided by Zephyr are only available on the PROCPU.

As a mitigation, applications running on the APPCPU may use ESP32 ROM functions such as ets_printf() to emit diagnostic or debug output.

For more information, check the ESP32 Datasheet [1] or the ESP32 Technical Reference Manual [2].

Supported Features

The lolin32_lite board supports the hardware features listed below.

on-chip / on-board
Feature integrated in the SoC / present on the board.
2 / 2
Number of instances that are enabled / disabled.
Click on the label to see the first instance of this feature in the board/SoC DTS files.
vnd,foo
Compatible string for the Devicetree binding matching the feature.
Click on the link to view the binding documentation.

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 lolin32_lite board supports the runners and associated west commands listed below.

flash debug

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:

  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 <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>

Debugging

OpenOCD Debugging

Espressif chips require a custom OpenOCD build with ESP32-specific patches. Download the latest release from OpenOCD for ESP32 [3].

For detailed JTAG setup instructions, see JTAG debugging for ESP32 [5].

Zephyr Thread Awareness

OpenOCD supports Zephyr RTOS thread awareness, allowing GDB to:

  • List all threads with info threads

  • Display thread names, priorities, and states

  • Switch between thread contexts

  • Show backtraces for any thread

Requirements:

Example:

# From the root of the zephyr repository
west build -b <board> samples/hello_world -- -DCONFIG_DEBUG_THREAD_INFO=y -DOPENOCD=<path/to/bin/openocd> -DOPENOCD_DEFAULT_PATH=<path/to/openocd/share/openocd/scripts>
west debug

Using a Custom OpenOCD

The Zephyr SDK includes a bundled OpenOCD, but it may not have ESP32 support. To use the Espressif OpenOCD, specify the path when building:

# From the root of the zephyr repository
west build -b <board> samples/hello_world -- -DOPENOCD=/path/to/openocd -DOPENOCD_DEFAULT_PATH=/path/to/openocd/scripts
west debug

References