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:
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 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