Hardware Design

  • hardware
  • design

What special precautions should be taken in the peripheral design of ESP32-S3?

  • Make sure GPIO45 is not pulled high by external circuitry during power-up.
  • In the R8 variants of ESP32-S3, the internal octal PSRAM uses GPIO33 to GPIO37, so those pins cannot be used for other functions.
  • CHIP_PU must be delayed by 50 us during power-up. An external RC delay circuit is therefore required. A recommended starting point is 10 KΩ for the resistor and 1 uF for the capacitor.

What special precautions should be taken in the peripheral design of ESP32?

  • Make sure GPIO12 is not pulled high by external circuitry during power-up.
  • If the ESP32 has internal or external PSRAM, GPIO16 requires a pull-up resistor.
  • CHIP_PU must be delayed by 50 us during power-up, so an external RC delay circuit is required. A recommended starting point is 10 KΩ for the resistor and 1 uF for the capacitor.

What special precautions should be taken in the peripheral design of ESP32-S2?

  • Make sure GPIO45 is not pulled high by external circuitry during power-up.
  • CHIP_PU must be delayed by 50 us during power-up, so an external RC delay circuit is required. A recommended starting point is 10 KΩ for the resistor and 1 uF for the capacitor.

When flashing firmware on a brand-new module over USB, why does the PC repeatedly detect the USB serial port connecting and disconnecting?

This usually happens because the new module has never been flashed before, so the flash does not contain a valid firmware image and the module cannot boot normally. In this state, the internal timer periodically resets the module every few seconds. Each reset reinitializes the USB Serial JTAG peripheral, so on the PC the USB serial port appears to connect, disconnect, and reconnect repeatedly.

For first-time USB flashing, pull the BOOT pin low before powering up so that the module enters download mode. The firmware can then be flashed normally. After flashing is complete, the USB serial port will stop reconnecting repeatedly.

What hardware design considerations are important when connecting an ESP32 module to Ethernet?

When an ESP32 module is connected to Ethernet, the RMII interface uses fixed pins. Among them, GPIO0 serves both as the BOOT pin and as the RMII TX_CLK pin.

If the module and the PHY chip power up at the same time, GPIO0 may be pulled low, causing the module to enter download mode. Therefore, the power-up sequence between the ESP32 module and the PHY chip must be considered carefully.

It is recommended to use an ESP32 GPIO to control the PHY enable pin so that the PHY is not powered at exactly the same time as the module.