Hardware Connection

[中文]

This document introduces what hardware you need to prepare and how to connect them in order to download AT firmware, send AT commands, and receive AT responses.

The commands supported by each series of AT firmware vary, and its compatibility with modules or chips also differs. For more information, refer to ESP-AT Firmware Differences.

If you don’t want to use the default AT pin, you can refer to the How to Set AT Port Pins document to change the pin.

What You Need

List of Components Required for ESP-AT Testing

Component	Function
ESP32-C2 board	Slave MCU.
USB cable (ESP32-C2 board to PC)	Download/Log output connection.
PC	Act as Host MCU. Download firmware to Slave MCU.
USB cable (PC to serial port converter)	AT command/response connection.
USB to serial port converter	Convert between USB signals and TTL signals.
Jumper wires (serial port converter to ESP32-C2 board)	AT command/response connection.

Connection of Components for ESP-AT Testing

Note:

• The official default AT Binary Lists only supports 26 MHz crystal oscillator. If your crystal oscillator of ESP32-C2 is 40 MHz, please refer to Compile ESP-AT Project Locally document to compile ESP32-C2 AT firmware, and configurate in the step 5:

  python build.py menuconfig -> Component config -> Hardware Settings -> Main XTAL Config -> Main XTAL frequency -> 40 MHz
  

• In the above picture, four jump wires are used to connect the ESP32-C2 board and USB to serial converter. If you do not use hardware flow control, two wires connecting TX/RX and a simpler converter will be enough.

• If you use an ESP32-C2 module instead of a development board and flash firmware via UART, you need to reserve the UART pins (refer to https://www.espressif.com/sites/default/files/documentation/esp8684_datasheet_en.pdf > Section Pin Description for more details) and one of the following conditions needs to be met:

  • Reserve the Strapping pins (refer to https://www.espressif.com/sites/default/files/documentation/esp8684_datasheet_en.pdf > Section Strapping Pins for more details), and enter the download mode by controlling the Strapping pin level.

  • Enter the download mode by sending AT+RST=1,1 command.

ESP32-C2-4MB/ESP32-C2-4MB-G2 Series

ESP32-C2-4MB/ESP32-C2-4MB-G2 series refer to the module or board that has a built-in ESP32-C2/ESP8684 chip with a 4 MB flash, such as ESP32-C2 MINI series device and ESP32-C2 WROOM series device.

ESP32-C2-4MB/ESP32-C2-4MB-G2 AT uses two UART ports: UART0 is used to download firmware and log output; UART1 is used to send AT commands and receive AT responses. Both UART0 and UART1 use 115200 baud rate for communication by default. When a 26 MHz crystal oscillator (XTAL) is used, the ROM-stage log is output via UART0 (TX: GPIO20) at 74880 baud. If the XTAL is changed to 40 MHz, the log output switches to 115200 baud.

ESP32-C2-4MB/ESP32-C2-4MB-G2 Series Hardware Connection Pinout

Function of Connection	ESP32-C2 Board or Module Pins	Other Device Pins
Download/Log output 1	UART0 GPIO19 (RX) GPIO20 (TX)	PC TX RX
AT command/response 2	UART1 GPIO6 (RX) GPIO7 (TX) GPIO5 (CTS) GPIO4 (RTS)	USB to serial converter TX RX RTS CTS

Note 1: Connection between individual pins of the ESP32-C2 board and the PC is already established internally on the ESP32-C2 board. You only need to provide USB cable between the board and PC.

Note 2: Connection between CTS/RTS is optional, depending on whether you want to use hardware flow control.

ESP32-C2-4MB/ESP32-C2-4MB-G2 Series Hardware Connection

If you want to connect your device directly with ESP32-C2 module rather than the ESP32-C2 board that integrates it, please refer to the corresponding module datasheet for more details.

ESP32-C2-2MB/ESP32-C2-2MB-G2 Series

ESP32-C2-2MB/ESP32-C2-2MB-G2 series refers to the module or board that has a built-in ESP32-C2/ESP8684 chip with a 2 MB flash.

ESP32-C2-2MB/ESP32-C2-2MB-G2 AT uses two UART ports: UART0 is used to download firmware and log output; UART1 is used to send AT commands and receive AT responses. Both UART0 (GPIO8, used to output log) and UART1 use 115200 baud rate for communication by default. When a 26 MHz crystal oscillator (XTAL) is used, the ROM-stage log is output via UART0 (TX: GPIO20) at 74880 baud. If the XTAL is changed to 40 MHz, the log output switches to 115200 baud.

ESP32-C2-2MB/ESP32-C2-2MB-G2 Series Hardware Connection Pinout

Function of Connection	ESP32-C2 Board or Module Pins	Other Device Pins
Download/Log output 1	UART0 GPIO19 (RX) GPIO20 (TX)	PC TX RX
AT command/response 2	UART1 GPIO6 (RX) GPIO7 (TX) GPIO19 (CTS) GPIO20 (RTS)	USB to serial converter TX RX RTS CTS
Log output	UART0 GPIO8 (TX)	USB to serial converter RX

Note 1: Connection between individual pins of the ESP32-C2 board and the PC is already established internally on the ESP32-C2 board. You only need to provide USB cable between the board and PC.

Note 2: Connection between CTS/RTS is optional, depending on whether you want to use hardware flow control.

ESP32-C2-2MB/ESP32-C2-2MB-G2 Series Hardware Connection

If you want to connect your device directly with ESP32-C2 module rather than the ESP32-C2 board that integrates it, please refer to the corresponding module datasheet for more details.

ESP32-C2-2MB-BLE/ESP32-C2-2MB-BLE-G2 Series

ESP32-C2-2MB-BLE/ESP32-C2-2MB-BLE-G2 series has the same hardware connection as the ESP32-C2-4MB/ESP32-C2-4MB-G2 series, with the only difference being the supported software features.

The AT firmware for this series is not released. You can choose one of the following ways to obtain the AT firmware for this series:

• Refer to the documentation How to Download the Latest Temporary Version of AT Firmware from GitHub, and download the esp32c2-2mb-ble-at/esp32c2-2mb-ble-g2-at firmware.

• Compile ESP-AT Project Locally, and in the third step of the environment installation, select Platform name as PLATFORM_ESP32C2 and Module name as ESP32-C2-2MB-BLE/ESP32-C2-2MB-BLE-G2.

ESP32-C2-2MB-NO-OTA-G2 Series

ESP32-C2-2MB-NO-OTA-G2 series has the same hardware connection as the ESP32-C2-4MB/ESP32-C2-4MB-G2 series, with the only difference being the supported software features.

The AT firmware for this series is not released. You can choose one of the following ways to obtain the AT firmware for this series:

• Refer to the documentation How to Download the Latest Temporary Version of AT Firmware from GitHub, and download the esp32c2-2mb-no-ota-g2-at firmware.

• Compile ESP-AT Project Locally, and in the third step of the environment installation, select Platform name as PLATFORM_ESP32C2 and Module name as ESP32C2-2MB-NO-OTA-G2.

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