The ESP32S3 DevKit is a development board for the ESP32-S3 SoC from Espressif, based on a ESP32-S3-WROOM-1 module.



  • ESP32-S3-WROOM-1 Module

  • USB-to-UART bridge via micro USB port

  • Power LED

  • EN and BOOT buttons (BOOT accessible to user)

  • SPI FLASH (size varies according to model

Serial Console

UART0 is, by default, the serial console. It connects to the on-board CP2102 converter and is available on the USB connector USB CON8 (J1).

It will show up as /dev/ttyUSB[n] where [n] will probably be 0.

Buttons and LEDs

Board Buttons

There are two buttons labeled Boot and EN. The EN button is not available to software. It pulls the chip enable line that doubles as a reset line.

The BOOT button is connected to IO0. On reset it is used as a strapping pin to determine whether the chip boots normally or into the serial bootloader. After reset, however, the BOOT button can be used for software input.

Board LEDs

There are several on-board LEDs for that indicate the presence of power and USB activity. None of these are available for use by software.


ESP32-S3 has two I2S peripherals accessible using either the generic I2S audio driver or a specific audio codec driver (CS4344 bindings are available at the moment). The generic I2S audio driver enables the use of both the receiver module (RX) and the transmitter module (TX) without using any specific codec. Also, it’s possible to use the I2S character device driver to bypass the audio subsystem and write directly to the I2S peripheral.

The following configurations use the I2S peripheral::


All of the configurations presented below can be tested by running the following commands:

$ ./tools/ esp32s3-devkit:<config_name>
$ make flash ESPTOOL_PORT=/dev/ttyUSB0 -j

Where <config_name> is the name of board configuration you want to use, i.e.: nsh, buttons, wifi… Then use a serial console terminal like picocom configured to 115200 8N1.


This configuration uses the I2S0 peripheral and an externally connected audio codec to play an audio file streamed over an HTTP connection while connected to a Wi-Fi network.

Audio Codec Setup

The CS4344 audio codec is connected to the following pins:

ESP32-S3 Pin

CS4344 Pin




Master Clock



Serial Clock



Left Right Clock (Word Select)



Serial Data In on CS4344. (DOUT on ESP32-S3)

Simple HTTP server

Prepare a PCM-encoded (.wav) audio file with 16 or 24 bits/sample (sampled at 16~48kHz). This file must be placed into a folder in a computer that could be accessed on the same Wi-Fi network the ESP32 will be connecting to.

Python provides a simple HTTP server. cd to the audio file folder on the PC and run:

$ python3 -m http.server
Serving HTTP on port 8000 (

Look for your PC IP address and test playing the prepared audio on your browser:


After successfully built and flashed, connect the board to the Wi-Fi network:

nsh> wapi psk wlan0 mypasswd 3
nsh> wapi essid wlan0 myssid 1
nsh> renew wlan0

Once connected, open NuttX’s player and play the file according to the filename and the IP address of the HTTP server:

nsh> nxplayer
nxplayer> play


This configuration shows the use of the buttons subsystem. It can be used by executing the buttons application and pressing on any of the available board buttons:

nsh> buttons
buttons_main: Starting the button_daemon
buttons_main: button_daemon started
button_daemon: Running
button_daemon: Opening /dev/buttons
button_daemon: Supported BUTTONs 0x01
nsh> Sample = 1
Sample = 0


This configuration sets the CoreMark benchmark up for running on the maximum number of cores for this system. It also enables some optimization flags and disables the NuttShell to get the best possible score.


As the NSH is disabled, the application will start as soon as the system is turned on.


Development environment ready for C++ applications. You can check if the setup was successful by running cxxtest:

nsh> cxxtest
Test ofstream ================================
printf: Starting test_ostream
printf: Successfully opened /dev/console
cout: Successfully opened /dev/console
Writing this to /dev/console
Test iostream ================================
Hello, this is only a test
Print an int: 190
Print a char: d
Test std::vector =============================
v1=1 2 3
Hello World Good Luck
Test std::map ================================
Test C++17 features ==========================
File /proc/meminfo exists!
Invalid file! /invalid
File /proc/version exists!


This is a test for the GPIO driver. Three GPIOS are defined: 1) GPIO15 is set as an output, 2) GPIO18 as input and, 3) GPIO21 as an input triggered by a rising edge.

This example also builds the EXAMPLES_GPIO application from the nuttx-apps.

To write to the GPIO (GPIO 15, as defined by the board implementation):

nsh> gpio -o 1 /dev/gpio0
nsh> gpio -o 0 /dev/gpio0

To read from the GPIO (GPIO 18, as defined by the board implementation):

nsh> gpio /dev/gpio1
Driver: /dev/gpio1
  Input pin:     Value=1

Finally, we can use the interrupt pin (GPIO21) to send a signal when the interrupt fires:

nsh> gpio -w 14 /dev/gpio2
Driver: /dev/gpio2
  Interrupt pin: Value=0
  Verify:        Value=1

The pin is configured to trigger an interrupt on the rising edge, so after issuing the above command, connect it to 3.3V.


This configuration can be used to scan and manipulate I2C devices. You can scan for all I2C devices using the following command:

nsh> i2c dev 0x00 0x7f


This is identical to the nsh configuration except that (1) NuttX is built as PROTECTED mode, monolithic module and the user applications are built separately and, as a consequence, (2) some features that are only available in the FLAT build are disabled.

Protected Mode support for ESP32-S3 relies on the World Controller (WC) and Permission Control (PMS) peripherals for implementing isolation between Kernel and Userspace.

By working together with the MMU and Static MPUs of the ESP32-S3, the WC/PMS is able to restrict the application access to peripherals, on-chip memories (Internal ROM and Internal SRAM) and off-chip memories (External Flash and PSRAM).


The World Controller and Permission Control do not prevent the application from accessing CPU System Registers.


This configuration is the same as the nsh configuration, but it generates the application image in a format that can be used by MCUboot. It also makes the make bootloader command to build the MCUboot bootloader image using the Espressif HAL.


Basic NuttShell configuration (console enabled in UART0, exposed via USB connection by means of CP2102 converter, at 115200 bps).


This configuration uses the I2S1 peripheral as an I2S receiver and the I2S0 peripheral as an I2S transmitter. The idea is to capture an I2S data frame using an I2S peripheral and reproduce the captured data on the other.

Receiving data on I2S1

The I2S1 will act as a receiver (in slave mode, i.e., waiting for the BCLK and WS signals from the transmitter), capturing data from DIN, which needs to be connected to an external source as follows:

ESP32-S3 Pin

Signal Pin




Bit Clock (SCLK)



Word Select (LRCLK)



Data IN

Transmitting data on I2S0

The I2S0 will act as a transmitter (in master mode, i.e., providing the BCLK and WS signals), replicating the data captured on I2S1. The pinout for the transmitter is as follows:

ESP32 Pin

Signal Pin




Master Clock



Bit Clock (SCLK)



Word Select (LRCLK)



Data Out


The audio codec CS4344 can be connected to the transmitter pins to reproduce the captured data if the receiver’s source is a PCM-encoded audio data.


The nxlooper application captures data from the audio device with input capabilities (the I2S1 in this example) and forwards the audio data frame to the audio device with output capabilities (the I2S0 in this example).

After successfully built and flashed, run on the boards’ terminal:

nsh> nxlooper
nxlooper> loopback


loopback command default arguments for the channel configuration, data width and sample rate are, respectively, 2 channels, 16 bits/sample and 48KHz. These arguments can be supplied to select different audio formats, for instance:

nxlooper> loopback 2 16 44100


This config demonstrate the use of oneshot timers present on the ESP32-S3. To test it, just run the oneshot example:

nsh> oneshot
Opening /dev/oneshot
Maximum delay is 4294967295999999
Starting oneshot timer with delay 2000000 microseconds


This config tests the PSRAM driver over SPIRAM interface in quad mode. You can use the mm command to test the PSRAM memory:

nsh> mm
      Total space allocated from system = 8803232
      Number of non-inuse chunks        = 2
      Largest non-inuse chunk           = 8388592
      Total allocated space             = 9672
      Total non-inuse space             = 8793560
(0)Allocating 5011 bytes


(31)Releasing memory at 0x3fc8c088 (size=24 bytes)
      Total space allocated from system = 8803232
      Number of non-inuse chunks        = 2
      Largest non-inuse chunk           = 8388592
      Total allocated space             = 9672
      Total non-inuse space             = 8793560


Similar to the `psram_quad` configuration but using the SPIRAM interface in octal mode.


This configuration demonstrates the use of PWM through a LED connected to GPIO2. To test it, just execute the pwm application:

nsh> pwm
pwm_main: starting output with frequency: 10000 duty: 00008000
pwm_main: stopping output


This configuration shows the use of the ESP32-S3’s True Random Number Generator with entropy sourced from Wi-Fi and Bluetooth noise. To test it, just run rand to get 32 randomly generated bytes:

nsh> rand
Reading 8 random numbers
Random values (0x3ffe0b00):
0000  98 b9 66 a2 a2 c0 a2 ae 09 70 93 d1 b5 91 86 c8  ..f......p......
0010  8f 0e 0b 04 29 64 21 72 01 92 7c a2 27 60 6f 90  ....)d!r..|.'`o.


This configuration demonstrates the use of the RTC driver through alarms. You can set an alarm, check its progress and receive a notification after it expires:

nsh> alarm 10
alarm_daemon started
alarm_daemon: Running
Opening /dev/rtc0
Alarm 0 set in 10 seconds
nsh> alarm -r
Opening /dev/rtc0
Alarm 0 is active with 10 seconds to expiration
nsh> alarm_daemon: alarm 0 received


Another NSH configuration, similar to nsh, but also enables SMP operation. It differs from the nsh configuration only in these additional settings:

SMP is enabled:


The apps/testing/smp test is included:



This config tests the external SPI that comes with the ESP32-S3 module connected through SPI1.

By default a SmartFS file system is selected. Once booted you can use the following commands to mount the file system:

nsh> mksmartfs /dev/smart0
nsh> mount -t smartfs /dev/smart0 /mnt

Note that mksmartfs is only needed the first time.


With this configuration you can run these commands to be able to connect your smartphone or laptop to your board:

nsh> ifup wlan1
nsh> dhcpd_start wlan1
nsh> wapi psk wlan1 mypasswd 3
nsh> wapi essid wlan1 nuttxap 1

In this case, you are creating the access point nuttxapp in your board and to connect to it on your smartphone you will be required to type the password mypasswd using WPA2.


Please refer to ESP32 Wi-Fi SoftAP Mode for more information.

The dhcpd_start is necessary to let your board to associate an IP to your smartphone.


This configuration enables the support for tickless scheduler mode.


This config test the general use purpose timers. It includes the 4 timers, adds driver support, registers the timers as devices and includes the timer example.

To test it, just run the following:

nsh> timer -d /dev/timerx

Where x in the timer instance.


This config is an example to use toywasm.

This example uses littlefs on the SPI flash to store wasm modules.

Note: This example assumes a board with 32MB flash. To use a smaller one, tweak the –img-size option and CONFIG_ESP32S3_STORAGE_MTD_SIZE.

Note: To use flash larger than 4MB, you need to install a custom bootloader.

  1. Create a littlefs image which contains wasm modules. is used in the following example:

    % python3 \
      --img-filename ..../littlefs.bin \
      --img-size 31981568 \
      --block-size 4096 \
      --prog-size 256 \
      --read-size 256 \
      --name-max 32 \
      --disk-version 2.0 \
  2. Build a NuttX binary as usual with this config.

  3. Write the NuttX binary and the filesystem image to the board:

    % \
      -c esp32s3 \
      -p /dev/tty.SLAB_USBtoUART \
      -b 921600 \
      write_flash \
      -fs detect \
      -fm dio \
      -ff 40m \
      0x10000 nuttx.bin \
      0x180000 ..../littlefs.bin
  4. Mount the filesystem and run a wasm module on it:

    nsh> mount -t littlefs /dev/esp32s3flash /mnt
    nsh> toywasm --print-stats --wasi /mnt/....


This configuration enables the support for the TWAI (Two-Wire Automotive Interface) driver. You can test it by connecting TWAI RX and TWAI TX pins which are GPIO0 and GPIO2 by default to a external transceiver or connecting TWAI RX to TWAI TX pin by enabling the Device Drivers -> CAN Driver Support -> CAN loopback mode option and running the can example:

nsh> can
nmsgs: 0
min ID: 1 max ID: 2047
Bit timing:
  Baud: 1000000
  TSEG1: 15
  TSEG2: 4
    SJW: 3
  ID:    1 DLC: 1


Basic NuttShell configuration console enabled over USB Device (USB CDC/ACM).

Before using this configuration, please confirm that your computer detected that USB JTAG/serial interface used to flash the board:

usb 3-5.2.3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
usb 3-5.2.3: Product: USB JTAG/serial debug unit
usb 3-5.2.3: Manufacturer: Espressif
usb 3-5.2.3: SerialNumber: XX:XX:XX:XX:XX:XX
cdc_acm 3-5.2.3:1.0: ttyACM0: USB ACM device

Then you can run the configuration and compilation procedure:

$ ./tools/ esp32s3-devkit:usbnsh
$ make flash ESPTOOL_PORT=/dev/ttyACM0 -j8

Then run the minicom configured to /dev/ttyACM0 115200 8n1 and press <ENTER> three times to force the nsh to show up:

NuttShell (NSH) NuttX-12.1.0
nsh> ?
help usage:  help [-v] [<cmd>]

    .         break     dd        exit      ls        ps        source    umount
    [         cat       df        false     mkdir     pwd       test      unset
    ?         cd        dmesg     free      mkrd      rm        time      uptime
    alias     cp        echo      help      mount     rmdir     true      usleep
    unalias   cmp       env       hexdump   mv        set       truncate  xd
    basename  dirname   exec      kill      printf    sleep     uname

Builtin Apps:
    nsh  sh
nsh> uname -a
NuttX 12.1.0 38a73cd970 Jun 18 2023 16:58:46 xtensa esp32s3-devkit


Enables Wi-Fi support. You can define your credentials this way:

$ make menuconfig
-> Application Configuration
    -> Network Utilities
        -> Network initialization (NETUTILS_NETINIT [=y])
            -> WAPI Configuration

Or if you don’t want to keep it saved in the firmware you can do it at runtime:

nsh> wapi psk wlan0 mypasswd 3
nsh> wapi essid wlan0 myssid 1
nsh> renew wlan0


Please refer to ESP32 Wi-Fi Station Mode for more information.


This config test the watchdog timers. It includes the 2 MWDTS, adds driver support, registers the WDTs as devices and includes the watchdog example.

To test it, just run the following:

nsh> wdog -i /dev/watchdogx

Where x is the watchdog instance.

To test the XTWDT(/dev/watchdog3) an interrupt handler needs to be implemented because XTWDT does not have system reset feature. To implement an interrupt handler WDIOC_CAPTURE command can be used. When interrupt rises, XTAL32K clock can be restored with WDIOC_RSTCLK command.