Adafruit Feather ESP32S2

Overview

The Adafruit Feather ESP32-S2 boards are ESP32-S2 development boards in the Feather standard layout, sharing peripheral placement with other devices labeled as Feathers or FeatherWings. The board is equipped with an ESP32-S2 mini module, a LiPo battery charger, a fuel gauge, a USB-C and SparkFun Qwiic [10]-compatible STEMMA QT [11] connector for the I2C bus.

Hardware

  • ESP32-S2 mini module, featuring the 240MHz Tensilica processor

  • 320KB SRAM, 4MB flash + 2MB PSRAM

  • USB-C directly connected to the ESP32-S2 for USB

  • LiPo connector and built-in battery charging when powered via USB-C

  • LC709203F or MAX17048 fuel gauge for battery voltage and state-of-charge reporting

  • Built-in NeoPixel indicator RGB LED

  • STEMMA QT connector for I2C devices, with switchable power for low-power mode

Note

  • The Adafruit ESP32-S2 Feather with BME280 Sensor [7] is the same board as the Adafruit ESP32-S2 Feather [6] but with an already equipped BME280 Sensor, but is not stated as a separate board, instead the BME280 needs to be added via a devicetree overlay. All boards, except the Adafruit ESP32-S2 Feather with BME280 Sensor [7] have a space for it, but will not be shipped with.

  • As of May 31, 2023 - Adafruit has changed the battery monitor chip from the now-discontinued LC709203F to the MAX17048. Check the back silkscreen of your Feather to see which chip you have.

  • For the MAX17048 and LC709203F a driver in zephyr exists and is supported, but needs to be added via a devicetree overlay.

  • For the Adafruit ESP32-S2 Feather [6] there are two different Revisions rev B and rev C. The rev C board has revised the power circuitry for the NeoPixel and I2C QT port. Instead of a transistor the rev C has a LDO regulator. To enable the NeoPixel and I2C QT port on rev B boards GPIO7 (i2c_reg) needs to be set to LOW and on rev C boards it needs to be set HIGH.

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 adafruit_feather_esp32s2 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.

Note

USB-OTG is until now not supported. To see a serial output a FTDI-USB-RS232 or similar needs to be connected to the RX/TX pins on the feather connector.

Connections and IOs

The Adafruit ESP32-S2 Feather [6] User Guide has detailed information about the board including pinouts and the schematic.

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 adafruit_feather_esp32s2 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>

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

espressif-flash-4M

Board with 4MB of flash

espressif-flash-8M

Board with 8MB of flash

espressif-flash-16M

Board with 16MB of flash

espressif-flash-32M

Board with 32MB of flash

espressif-flash-64M

Board with 64MB of flash

espressif-flash-128M

Board with 128MB of flash

PSRAM memory size

espressif-psram-2M

Board with 2MB of PSRAM

espressif-psram-4M

Board with 4MB of PSRAM

espressif-psram-8M

Board with 8MB of PSRAM

PSRAM utilization

espressif-psram-reloc

Relocate flash to PSRAM

espressif-psram-wifi

Wi-Fi buffers in PSRAM

To apply a board variant, use the -S flag with west build:

west build -b <board> -S espressif-flash-32M -S espressif-psram-4M samples/hello_world

Note

These snippets are only 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 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

Testing the On-Board-LED

There is a sample available to verify that the LEDs on the board are functioning correctly with Zephyr:

Rev B

# From the root of the zephyr repository
west build -b adafruit_feather_esp32s2@B samples/basic/blinky
west flash

Rev C

# From the root of the zephyr repository
west build -b adafruit_feather_esp32s2@C samples/basic/blinky
west flash

Testing the NeoPixel

There is a sample available to verify that the NeoPixel on the board are functioning correctly with Zephyr:

Rev B

# From the root of the zephyr repository
west build -b adafruit_feather_esp32s2@B samples/drivers/led/led_strip
west flash

Rev C

# From the root of the zephyr repository
west build -b adafruit_feather_esp32s2@C samples/drivers/led/led_strip
west flash

Testing the Fuel Gauge

There is a sample available to verify that the MAX17048 or LC709203F fuel gauge on the board are functioning correctly with Zephyr

Note

As of May 31, 2023 Adafruit changed the battery monitor chip from the now-discontinued LC709203F to the MAX17048.

Rev B

For the Rev B a devicetree overlay for the LC709203F fuel gauge already exists in the samples/drivers/fuel_gauge/boards folder.

# From the root of the zephyr repository
west build -b adafruit_feather_esp32s2@B samples/drivers/fuel_gauge
west flash

Rev C

For the Rev C a devicetree overlay for the MAX17048 fuel gauge already exists in the samples/drivers/fuel_gauge/boards folder.

# From the root of the zephyr repository
west build -b adafruit_feather_esp32s2@C samples/drivers/fuel_gauge
west flash

For the LC709203F a devicetree overlay needs to be added to the build. The overlay can be added via the --extra-dtc-overlay argument and should most likely includes the following:

/ {
   aliases {
      fuel-gauge0 = &lc709203f;
   };
};

&i2c0 {
   lc709203f: lc709203f@0b {
      compatible = "onnn,lc709203f";
      status = "okay";
      reg = <0x0b>;
      power-domains = <&i2c_reg>;
      apa = "500mAh";
      battery-profile = <0x01>;
   };
};

# From the root of the zephyr repository
west build -b adafruit_feather_esp32s2@C --extra-dtc-overlay="boards/name_of_your.overlay" samples/drivers/fuel_gauge
west flash

Testing Wi-Fi

There is a sample available to verify that the Wi-Fi on the board are functioning correctly with Zephyr:

Note

The Prerequisites must be met before testing Wi-Fi.

Rev B

# From the root of the zephyr repository
west build -b adafruit_feather_esp32s2@B samples/net/wifi/shell
west flash

Rev C

# From the root of the zephyr repository
west build -b adafruit_feather_esp32s2@C samples/net/wifi/shell
west flash

References