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MCU + Universal TCP_AT Module Porting (FreeRTOS)

Last updated: 2021-08-20 18:31:34

    For MCUs that have no network communication capabilities, the "MCU + communication module" combination is often used. Communication modules (including Wi-Fi/2G/4G/NB-IoT) generally provide serial port-based AT instruction protocols for MCUs to communicate over the network. For this scenario, the C-SDK encapsulates the AT-socket network layer, where the core protocol and service layer don't need to be ported. This document describes how to port C-SDK for connection to IoT Hub in the target environment of MCU (FreeRTOS) + universal TCP AT module.

    SDK Download

    Download the latest version of the device C-SDK.

    SDK Feature Configuration

    Use the general TCP module to compile and configure the options as follows:

    Name Configuration Description
    BUILD_TYPE debug/release Set as needed
    EXTRACT_SRC ON Enable code extraction
    COMPILE_TOOLS gcc/MSVC Set as needed and ignore in case of IDE
    PLATFORM Linux/Windows Set as needed and ignore in case of IDE
    FEATURE_OTA_COMM_ENABLED ON/OFF Set as needed
    FEATURE_AUTH_MODE KEY Key authentication is recommended for resource-constrained devices
    FEATURE_AUTH_WITH_NOTLS ON/OFF Enable TLS as needed
    FEATURE_EVENT_POST_ENABLED ON/OFF Enable event reporting as needed
    FEATURE_AT_TCP_ENABLED ON Whether to enable TCP feature in AT module
    FEATURE_AT_UART_RECV_IRQ ON Whether to enable receipt interruption feature in AT module
    FEATURE_AT_OS_USED ON Whether to enable multithreaded feature in AT module
    FEATURE_AT_DEBUG OFF The AT module debugging feature is disabled by default, and it needs to be enabled during debugging

    Code Extraction

    1. Run the following command on Linux:
      mkdir build
      cd build
      cmake ..
      
    2. You can find the relevant code files in output/qcloud_iot_c_sdk with the following directory hierarchy:
      qcloud_iot_c_sdk
      ├── include
      │   ├── config.h
      │   ├── exports
      ├── platform
      └── sdk_src
       └── internal_inc
      
      Note:

      • include directory: contains the SDK APIs and variable parameters, where config.h is the compilation macros generated according to the compilation options.
      • platform directory: contains platform-related code, which can be modified and adapted according to the specific conditions of the device.
      • sdk_src directory: contains the SDK core logic and protocol-related code, which generally don't need to be modified, where internal_inc is the header file used internally by the SDK.
    3. You can copy qcloud_iot_c_sdk to the compilation and development environment of your target platform and then modify the compilation options as needed.

    HAL Porting

    Please refer to Overview to port first.
    For network HAL APIs, the AT_Socket framework provided by the SDK has been selected through the above compilation options. The SDK will call the at_socket API of network_at_tcp.c. You don't need to port the at_socket layer, but you need to implement the AT serial port driver and AT module driver. For the AT module driver, you only need to implement the driver API of the driver structure at_device_op_t in at_device of the AT framework. You can refer to the supported modules in the at_device directory.
    Currently, the SDK provides underlying API implementation for the Wi-Fi module ESP8266, which is widely used in the IoT field, for reference when you port to other communication modules.

    Business Logic Development

    You can refer to the routines in the SDK's samples directory for development.

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