[嵌入式]The hardware conditions for the ESP32-C3 chip to enter the “ Download Mode“

The ESP32-C3 downloads firmware via UART0 (U0TXD (GPIO21) and U0RXD (GPIO20)) by default. Please refer to the 《ESP32-C3 Datasheet》.

• On the Windows environment, you can use the “Flash Download Tool” to download the firmware (The bin file).

• On the Ubuntu environment, you can use the “ esptool ” to download the firmware (The bin file). For example:

  esptool.py -p /dev/ttyUSB1 -b 460800 --before default_reset --after hard_reset write_flash --flash_mode dio --flash_size detect --flash_freq 40m 0x1000 /home/caiguanhong/Documents/test_version_bbe4b67/bootloader.bin 0x8000 /home/caiguanhong/Documents/test_version_bbe4b67/partition-table.bin 0x10000 /home/caiguanhong/Documents/test_version_bbe4b67/ssc.bin
  

1 The following hardware conditions must be met for the ESP32-C3 chip to start:

• The ESP32-C3 chip working voltage range is 3.0 V ~ 3.6 V; If you use a single power supply, the recommended voltage of the power supply for ESP32-C3 family is 3.3 V, and its recommended output current is 500 mA or more. Please refer to the 《ESP32-C3 Hardware Design Guidelines》.
  

• If using the ESP32-C3 series Chips , you need require an external 40 MHz crystal oscillator for chip startup. If using the ESP32-C3 series modules , there is no longer need to external starting crystal oscillator. The hardware working conditions of ESP32-C3 chip can refer to the《ESP32--C3--MINI-1 Datasheet》.

  
  
  

2 The following pins level requirements must be met when the ESP32-C3 series chips need enter the download mode :

VDD -> 3V3           （The Power Supply）
GND -> GND           （"Common ground" with power supply）
GPIO2 -> Pull Up     （Controls the SPI Flash startup mode）
GPIO8 -> Pull Up     （Start `Download Mode`）
GPIO9 -> Pull Down   （ Enter the `Download Dode`）
CHIP_EN -> Pull Up   （Enables the Chip， Do not leave the `CHIP_EN` pin floating）
TXD0 、RXD0          （Correct Connection）

【Note】

• The strapping combination of GPIO8 = 0 and GPIO9 = 0 is invalid and will trigger unexpected behavior.
  
  

• Please refer to the 《ESP32-C3 Datasheet》 about " Srtapping Pins " instructions.

3 Power-on Sequence

• The Chip_EN pin can be enabled only after the power supply reaches 50 us after 2.8 V.That is when VDD reaches 2.8 V, EN cannot exceed 0.7 V. Please refer to the 《ESP32-C3 Hardware Design Guidelines》 about " 2.2.1 Power-on Sequence " .

4 If the download fails, Please refer to the following methods for troubleshooting:

• After the serial port tool is powered on, please pull down the Chip_EN pin and reset it , the serial port will print logs. If print the “waiting for Download” logs , it proves that the chip is in download mode.

  ESP-ROM:esp32c3-20200918
  Build:Sep 18 2020
  rst:0x1 (POWERON),boot:0x4 (DOWNLOAD(USB/UART0/1))
  waiting for download
  

• After entering the download mode, if the COM port is in waiting for Power-on synchronization state on the “Flash Download Tool” , please check whether the COM port is correctly selected or occupied. And whether the UART0 download interface is correctly connected.
  

5 【Introductions】

• If you want to use ESP32-C3 module to design hardware automatic download circuit, please refer to the " ESP32-C3-DevKitM-1 Schematic Diagram ".
• For more hardware design references , please refer to the 《ESP32-C3 Hardware Design Guidelines》.
• If your computer environment does not recognize ESP32-C3 devices, Please refer to the "Establish Serial Connection with ESP32-C3" guide.