ESP32-S31

[中文]

Note

This document is automatically translated using AI. Please excuse any detailed errors. The official English version is still in progress.

ESP32-S31 Chip/Module Startup Conditions

  • The operating voltage range of the ESP32-S31 chip is 3.0 V ~ 3.6 V; when using a single power supply, it is recommended that the power supply voltage is 3.3 V, and the output current needs to reach 600 mA or more.

  • The operating voltage range of the ESP32-S31 module is 3.0 V ~ 3.6 V; when using a single power supply, it is recommended that the power supply voltage is 3.3 V, and the output current needs to reach 600 mA or more.

  • The CHIP_PU (EN) pin of the ESP32-S31 is the chip’s boot pin. When CHIP_PU (EN) is at a high level, the chip is enabled; when it is at a low level, the chip is turned off. Note: The CHIP_PU pin must not be left floating. When the ESP32-S3 is powered by a 3.3V system power supply, the CHIP_PU (EN) pin must be at a high level.

Hardware Connection

ESP32-S31 supports two firmware download methods: UART0 and USB.

  • When downloading firmware based on ESP32-S31 via UART0, users need to prepare:

    • 3.3V Power Supply

    • Serial debugging tool

    • Dupont wire

    When downloading firmware using the UART0 pin, the following wiring conditions must be met to satisfy the hardware requirements for chip power supply, power-on startup, and entering download mode.

    ESP32-S31

    3.3V External Power Supply

    Serial debugging tool

    3V3

    VDD

    GND

    GND

    GND

    EN

    VDD

    GPIO61 (pull down, default is weak pull-up)

    GND

    GPIO60 (pull up or float, default is weak pull-up)

    VDD

    TXD0 (GPIO58)

    RXD

    RXD0 (GPIO59)

    TXD

  • When downloading firmware based on ESP32-S31 via USB, users need to prepare:

    • 3.3V Power Supply

    • USB cable

    • Dupont wire

    When downloading firmware using the USB HS OTG pin, the following wiring conditions must be met to satisfy the hardware requirements for chip power supply, power-on startup, and entering download mode.

    ESP32-S31

    3.3V External Power Supply

    USB cable

    3V3

    VDD

    GND

    GND

    GND

    EN

    VDD

    GPIO61 (pull down, default is weak pull-up)

    GND

    GPIO60 (pull up or float, default is weak pull-up)

    VDD

    USB_DM

    USB_D- (White)

    USB_DP

    USB_D+ (Green)

    When downloading firmware using the USB_SERIAL_JTAG pin, the following wiring conditions must be met to satisfy the hardware requirements for chip power supply, power-on startup, and entering download mode.

    ESP32-S31

    3.3V External Power Supply

    USB cable

    3V3

    VDD

    GND

    GND

    GND

    EN

    VDD

    GPIO61 (pull down, default is weak pull-up)

    GND

    GPIO60 (pull up or float, default is weak pull-up)

    VDD

    GPIO13

    USB_D- (White)

    GPIO14

    USB_D+ (Green)

  • When testing with the ESP32-S31 Development Board, you can directly use a USB Type-C cable to connect to the USB-UART interface on the development board for firmware download. If you are downloading firmware via the USB interface for the first time, you need to manually pull down the GPIO61 pin, that is, hold down the Boot button and then power on, to manually enter the download mode.

Chip Power-On Startup Log

After powering on the ESP32-S31 chip/module, you can use the PC-side serial debugging software (such as XCOM) to view the UART0 serial output when the chip is powered on to confirm whether the chip has entered download mode. If the chip enters download mode upon power-up, UART0 will print the following log:

ESP-ROM:esp32s31-20251218
Build:Dec 18 2025
rst:0x1 (POWERON),boot:0x69 (DOWNLOAD(USB/UART0/SPI))
waiting for download

Note

  • After powering on the ESP32-S31 chip/module, if you do not see the log printing, you can trigger the log printing by pulling down and then pulling up the CHIP_PU (EN) pin for a hardware reset restart.

  • In addition, you can also view the chip power-on startup log to determine the strapping pin level state at power-on. For detailed instructions, please refer to: ESP32-S31 Boot Log instructions.

In terms of software, Espressif provides a PC-side Flash download tool, which can directly download firmware (.bin) to Flash. For usage instructions, refer to the Flash Download Tool User Guide.

After the firmware download is complete, if you want to run the burned firmware, you can pull up GPIO61 (default is high level) based on the aforementioned hardware wiring, and then pull down and pull up the CHIP_PU (EN) pin for hardware reset and restart, allowing the chip to re-enter the Flash boot mode. Finally, use the serial debugging software to view the UART0 log printout to check the firmware running status.

References

Official Documentation: