ESP32-S2-Saola

Overview

ESP32-S2-Saola is a small-sized ESP32-S2 based development board produced by Espressif. Most of the I/O pins are broken out to the pin headers on both sides for easy interfacing. Developers can either connect peripherals with jumper wires or mount ESP32-S2-Saola on a breadboard. For more information, check ESP32-S3-DevKitC [1].

Hardware

ESP32-S2 is a highly integrated, low-power, single-core Wi-Fi Microcontroller SoC, designed to be secure and cost-effective, with a high performance and a rich set of IO capabilities.

The features include the following:

  • RSA-3072-based secure boot

  • AES-XTS-256-based flash encryption

  • Protected private key and device secrets from software access

  • Cryptographic accelerators for enhanced performance

  • Protection against physical fault injection attacks

  • Various peripherals:

    • 43x programmable GPIOs

    • 14x configurable capacitive touch GPIOs

    • USB OTG

    • LCD interface

    • camera interface

    • SPI

    • I2S

    • UART

    • ADC

    • DAC

    • LED PWM with up to 8 channels

For more information, check the datasheet at ESP32-S2 Datasheet [2] or the technical reference manual at ESP32-S2 Technical Reference Manual [3].

Supported Features

Current Zephyr’s ESP32-S2-Saola 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

PCNT

on-chip

qdec

SPI DMA

on-chip

spi

ADC

on-chip

adc

DAC

on-chip

dac

Wi-Fi

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 esp32s2_saola --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 esp32s2_saola samples/hello_world

The usual flash target will work with the esp32s2_saola board configuration. Here is an example for the Hello World application.

# From the root of the zephyr repository
west build -b esp32s2_saola 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! esp32s2_saola

Debugging

ESP32-S2 support on OpenOCD is available at OpenOCD ESP32 [5].

The following table shows the pin mapping between ESP32-S2 board and JTAG interface.

ESP32 pin

JTAG pin

MTDO / GPIO40

TDO

MTDI / GPIO41

TDI

MTCK / GPIO39

TCK

MTMS / GPIO42

TMS

Further documentation can be obtained from the SoC vendor in JTAG debugging for ESP32-S2 [4].

Here is an example for building the Hello World application.

# From the root of the zephyr repository
west build -b esp32s2_saola 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 esp32s2_saola samples/hello_world
west debug

References