The hardware conditions for the ESP32-C2 chip to enter the “ Download Mode“

ESP32-C2 downloads firmware via U0TXD(GPIO20)and U0RXD(GPIO19) by default. Please refer to the ESP32-C2

• On the Windows environment, you can use the Flash download tool to download the firmware (The bin file).
  
  
  

  • Run flash_download_tool.exe
    

  • Choose ChipType as ESP32-C2, LoadMode as UART, then press OK.
    

  1. Click to select the .bin file to be flashed.
  2. Enter the download address offset for the firmware to be flashed.
  3. Choose the COM port to which the development board is connected.
  4. Click “Start” at the bottom-left corner to begin the flashing process.

The green progress bar below will show the flashing progress, and it will be fully loaded when flashing is complete.

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

  esptool.py -p /dev/ttyUSB0 write_flash 0x0 bootloader.bin 0x8000 partition-table.bin 0x10000 ssc.bin
  

esptool command instructions can be found in the “Esptool.py Documentation”

1、The following pins level requirements must be met when the ESP32-C2 series chips need enter the download mode:

VDD -> 3V3 					（The Power Supply）
GND -> GND 					（"Common ground" with power supply）
GPIO8 -> pull up			（default floating）
GPIO9 -> pull down 			（default pull up）
EN -> pull up				（Enables the Chip， Do not leave the `EN` pin floating）
TXD0 -> RX
RXD0 -> TX

After ensuring the correct wiring connections, you can proceed with the firmware programming

Note:

• The strapping combination of GPIO8 = 0 and GPIO9 = 0 is invalid and will trigger unexpected behavior.
• After powering up the chip/module, you can verify whether it has entered Download Boot mode by using the UART0 serial port.

• Please refer to the 《ESP32-C2 Datasheet》 about "2.4 Strapping Pins
  " instructions.
  

2、The following hardware conditions must be met for the ESP32-C2 chip to start:

• The ESP32-C2 chip working voltage range is 3.0 V ~ 3.6 V；f you use a single power supply, the recommended voltage of the power supply for ESP32-C2 family is 3.3 V, and its recommended output current is 500 mA or more.

• When using ESP32-C2 series Chips, you need require an external 26 MHz crystal oscillator for chip startup. If using the ESP32-C2 series modules , there is no longer need to external starting crystal oscillator. The hardware working conditions of ESP32-C2 chip can refer to the《ESP8684-MINI-1》 page 2

• For more hardware design details, please refer to the 《ESP8684 Series Hardware Design Guidelines》.

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3、Power­on Sequence:

• The Chip_EN pin can be enabled only after the power supply reaches 50 us after 2.8 V. So when VDD reaches 2.8V, the voltage at EN must not exceed 0.7V. Please refer to the ESP32-C2 Datasheet about "2.3 Power Scheme"

• For hardware design reference on "Power-up Timing and System Reset", please refer to the 《ESP8684 Series Hardware Design Guidelines》
  

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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:esp8684-api2-20220127
  Build:Jan 27 2022
  rst:0x1 (POWERON),boot:0x4 (DOWNLOAD(UART0))
  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.

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Note:

• If you want to use ESP32-C2 module to design hardware automatic download circuit, please refer to the ESP8684-DevKitM-1 Schematics Diagram
• For more hardware design references , please refer to the 《ESP8684 Series Hardware Design Guidelines》
• If your computer environment does not recognize ESP32-C2 devices, Please refer to the Establish Serial Connection with ESP32-C2" guide (It applies to all ESP chips)