AT FAQ

[中文]

AT Firmware

There is no released firmware for my module. Where can I get the firmware for it?

If there is no released fimware for your module in the AT Binary Lists chapter, please consider the following options:

How to get the source code of AT firmware?

ESP-AT firmware is partially open-source. See esp-at for the open-source repository.

Does the AT firmware shipped in modules support flow control?

AT Commands and Responses

What is the reason why AT prompts busy?

  • The “busy” prompt indicates that the previous command is being executed, and the system cannot respond to the current input. The processing mechanism of the AT commands is serial, i.e. one command at a time.

  • Any input through serial ports is considered to be a command input, so the system will also prompt “busy” or “ERROR” when there is any extra invisible character input.

    • Serial input AT+GMR (change character CR LF) (space character), because AT+GMR (change character CR LF) is already a complete AT command, the system will execute the command. At this time, if the system has not completed the AT+GMR operation, it has received the following space character, which will be regarded as a new command input, and the system will prompt “busy”. But if the system has completed the AT+GMR operation, and then receives the following space character, the space character will be regarded as an error command, and the system will prompt “ERROR”.

    • After the MCU sends AT+CIPSEND and receives the busy p.. response, the MCU needs to resend the data. Because busy p.. represents the previous command is being executed, the current input is invalid. It is recommended to wait for the response of the last AT command before the MCU sends a new command again.

Why does the ESP-AT firmware always return the following message after the I powered up the device and sent the first command?

ERR CODE:0x010b0000
busy p...

  • This message means that the previous command is being executed.

  • Normally only “busy p…” is displayed. The ERR CODE is displayed because the error code prompt is enabled.

  • If you receive this message after sending the first command on power-up, the possible reasons are: the command is followed by the unnecessary newline/space/other symbols; or two or more AT commands are sent in succession.

What commands are supported by the default ESP-AT firmware on different modules, and from which version are they supported?

  • To learn what commands are supported by the default ESP-AT firmware on different modules, please refer to ESP-AT Firmware Differences.

  • To learn from which version a command is supported and what issues are fixed in each version, please refer to release notes.

When the host MCU sends an AT command to the ESP32-C3 device, there is no response. What is the reason?

A terminator (“ATrn”) must be added after an AT command when the host MCU sending AT commands to an ESP32-C3 device. Please see Check Whether AT Works.

Do AT commands support ESP-WIFI-MESH?

Currently, AT commands do not support ESP-WIFI-MESH.

Does AT support websocket commands?

Can AT command set Bluetooth LE transmit power?

Yes, the AT+RFPOWER command can set Bluetooth LE transmit power. ESP32-C3 Wi-Fi and Bluetooth LE share the same antenna.

How to support commands that are not supported by the default firmware but can be supported after configuring and compiling the ESP-AT project?

For example, if you need to support the WPA2 Enterprise function on the ESP32-C3 series, configure and compile the firmware by yourself. Open the WPA2 Enterprise function in menuconfig when compiling: ./build.py menuconfig > Component config > AT > [*]AT WPA2 Enterprise command support.

How to handle special characters in AT commands?

Please refer to the escape character syntax described in the AT Command Types section.

Can the serial port baudrate be modified in AT Commands? (Default: 115200)

Yes, you can use either of the two ways below to modify it:

After ESP32-C3 enters the passthrough mode using AT commands, can ESP32-C3 give a message if the connected hotspot is disconnected?

  • Yes, you can configure it with AT+SYSMSG, i.e., set AT+SYSMSG=4. In this way, the serial port will report “WIFI DISCONNECTrn” when the connected hotspot is disconnected.

  • Note that this command is added after AT v2.1.0. It is not available for v2.1.0 and earlier versions.

How to set ADV broadcast parameters after it exceeds 32 bytes?

The AT+BLEADVDATA command supports up to 32 bytes of ADV broadcast parameters. If you need to set a bigger parameter, please use command AT+BLESCANRSPDATA.

Hardware

How to view the error log of AT firmware?

  • For ESP32-C3, the error log is output through the download port. By default, UART0 is GPIO21 and GPIO20.

  • See Hardware Connection for more details.

The UART1 communication pin used by ESP-AT on the ESP32-C3 module is inconsistent with the default UART1 pin described in the ESP32-C3 module’s datasheet?

  • ESP32-C3 supports IO matrix. When compiling ESP-AT, you can configure UART1 pins in menuconfig, so they may be inconsistent with the pins described in the module datasheet.

  • See factory_param_data.csv for more details.

Performance

How long does it take for the AT to connect to Wi-Fi?

  • In an office scenario, the connection time is 5 seconds. However, in actual practice, Wi-Fi connection time depends on the router performance, network environment, module antenna performance, etc.

  • The maximum timeout time can be set by the <jap_timeout> parameter of AT+CWJAP.

Is it possible to change the TCP send window size in AT firmware?

  • Currently, it cannot be changed by AT commands, but you can configure and compile the ESP-AT project to generate a new firmware.

  • You can configure the menuconfig parameter: Component config > LWIP > TCP > Default send buffer size.

How to test and optimize the throughput of ESP32-C3 AT?

  • Many factors are affecting the AT throughput test. It is recommended to use the iperf example in esp-idf for testing. While testing, please use the passthrough mode, adjust the data length to 1460 bytes, and send data continuously.

  • If the test rate does not meet your requirements, please refer to How to Improve ESP-AT Throughput Performance.

Other

What interfaces of ESP32-C3 chips can be used to transmit AT commands?

  • ESP32-C3 can transmit AT commands through UART and SPI.

  • The default firmware uses UART for transmission. If you need SDIO or SPI interface to transmit AT commands, you can configure it through ./build.py menuconfig -> Component config -> AT when compiling the ESP-AT project by yourself.

  • See AT through SDIO , AT through SPI , or AT through socket for more details.

How do I specify the TLS protocol version for ESP32-C3 AT?

When compiling the esp-at project, you can disable the unwanted versions in the ./build.py menuconfig -> Component config -> mbedTLS.

How to modify the number of TCP connections in AT?

  • At present, the maximum number of TCP connections of the AT default firmware is 5.

  • The ESP32-C3 AT supports a maximum of 16 TCP connections, which can be configured in menuconfig as follows:

    • ./build.py menuconfig—> Component config—> AT—> (16)AT socket maximum connection number

    • ./build.py menuconfig—> LWIP—> (16)Max number of open sockets

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