ESP32-DevKitC-WROOM

Overview

ESP32 is a series of low cost, low power system on a chip microcontrollers with integrated Wi-Fi & dual-mode Bluetooth. The ESP32 series employs a Tensilica Xtensa LX6 microprocessor in both dual-core and single-core variations. ESP32 is created and developed by Espressif Systems, a Shanghai-based Chinese company, and is manufactured by TSMC using their 40nm process. For more information, check ESP32-DevKitC-WROOM [1].

The features include the following:

  • 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

    • Temperature sensor

    • 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

  • Cryptographic hardware acceleration (RNG, ECC, RSA, SHA-2, AES)

  • 5uA deep sleep current

For more information, check the datasheet at ESP32 Datasheet [2] or the technical reference manual at ESP32 Technical Reference Manual [3].

Asymmetric Multiprocessing (AMP)

ESP32-DevKitC-WROOM 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.

Supported Features

Current Zephyr’s ESP32-DevKitC-WROOM board supports the following features:

Interface

Controller

Driver/Component

UART

on-chip

serial port

GPIO

on-chip

gpio

PINMUX

on-chip

pinmux

USB-JTAG

on-chip

hardware interface

SPI Master

on-chip

spi

Timers

on-chip

counter

Watchdog

on-chip

watchdog

TRNG

on-chip

entropy

LEDC

on-chip

pwm

MCPWM

on-chip

pwm

PCNT

on-chip

qdec

SPI DMA

on-chip

spi

TWAI

on-chip

can

ADC

on-chip

adc

DAC

on-chip

dac

Wi-Fi

on-chip

Bluetooth

on-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 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 esp_wrover_kit --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 esp32_devkitc_wroom/esp32/procpu samples/hello_world

The usual flash target will work with the esp32_devkitc_wroom board configuration. Here is an example for the Hello World application.

# From the root of the zephyr repository
west build -b esp32_devkitc_wroom/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! esp32_devkitc_wroom

Debugging

ESP32 support on OpenOCD is available at OpenOCD ESP32 [5].

On the ESP32-DevKitC-WROOM board, the JTAG pins are not run to a standard connector (e.g. ARM 20-pin) and need to be manually connected to the external programmer (e.g. a Flyswatter2):

ESP32 pin

JTAG pin

3V3

VTRef

EN

nTRST

IO14

TMS

IO12

TDI

GND

GND

IO13

TCK

IO15

TDO

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 esp32_devkitc_wroom/esp32/procpu samples/hello_world
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 esp32_devkitc_wroom/esp32/procpu samples/hello_world
west debug

Note on Debugging with GDB Stub

GDB stub is enabled on ESP32.

  • When adding breakpoints, please use hardware breakpoints with command hbreak. Command break uses software breakpoints which requires modifying memory content to insert break/trap instructions. This does not work as the code is on flash which cannot be randomly accessed for modification.

References