14. Tencent cloud IOT device side learning - data template application development

The main purpose of this series is to record the learning notes of Tencent cloud Internet of things device , And on the device side SDK Make a supplementary explanation .

brief introduction

Data template related concepts , Please see the Data template

Data template function implementation , Please see the Data template function and implementation

The following describes how to develop applications based on data templates , It mainly includes Data template coding 、 Downlink data processing 、 Uplink data reporting .

Please refer to the source code ：

https://github.com/xyfancy/iot-hub-device-c-sdk/tree/master/app/data_template

Data template coding

The core idea ： Convert the data template definition to the corresponding C Code data type , such as Integer type ->int, Provide general interface according to Indexes visit （ The implementation is in beta edition , Subsequently, the script is used for automatic generation ）.

Source code ：data_template_config.c and data_template_config.h

Take the lamp switch attribute as an example ：

1. initialization

Properties include ：

• type： Corresponding data template type
• key： For the keyword corresponding to the attribute
• value： Value storage space
• need_report： Whether it is necessary to report , When the value changes , The escalation platform is required for synchronization （ Specially ： If it is only a downstream attribute , And the platform is not used to save the status , There is no need to report ）

struct DataTemplateProperty {
    DataTemplatePropertyType  type;
    const char*               key;
    DataTemplatePropertyValue value;
    int                       need_report;
};

According to the definition of data template on the console , Initialize switch properties ：

• type ： Boolean type
• keyword ：power_switch
• value ： You can use C In language int Storage , Where the value uses Joint type , Users need to select members according to the data template type .
• Report or not ： Because the switch can be modified manually when it is offline , Therefore, it is necessary to report during initialization ）

sg_usr_data_template_property[USR_PROPERTY_INDEX_POWER_SWITCH].value.value_bool = 0;
sg_usr_data_template_property[USR_PROPERTY_INDEX_POWER_SWITCH].key              = "power_switch";
sg_usr_data_template_property[USR_PROPERTY_INDEX_POWER_SWITCH].type             = DATA_TEMPLATE_TYPE_BOOL;
sg_usr_data_template_property[USR_PROPERTY_INDEX_POWER_SWITCH].need_report      = 1;

2. Interface call

By indexing data templates , Access the corresponding data template through the index

typedef enum {
    USR_PROPERTY_INDEX_POWER_SWITCH = 0, //  Switch index 
    USR_PROPERTY_INDEX_COLOR,
    USR_PROPERTY_INDEX_BRIGHTNESS,
    USR_PROPERTY_INDEX_NAME,
    USR_PROPERTY_INDEX_POSITION,
    USR_PROPERTY_INDEX_POWER,
} UsrPropertyIndex;

// initialization 
void usr_data_template_init(void);
// Get the data template value of non structure type 
DataTemplatePropertyValue usr_data_template_property_value_get(UsrPropertyIndex index);
// Set the data template value of non structure type 
void usr_data_template_property_value_set(UsrPropertyIndex index, DataTemplatePropertyValue value);
// Get the data template value of the structure type 
DataTemplatePropertyValue usr_data_template_property_struct_value_get(UsrPropertyIndex struct_index,
                                                                      int              property_index);
// Set the data template value of the structure type 
void usr_data_template_property_struct_value_set(UsrPropertyIndex struct_index, int property_index,
                                                 DataTemplatePropertyValue value);
// Get the data template value of the input parameter in the behavior                                                  
DataTemplatePropertyValue usr_data_template_action_input_value_get(UsrActionIndex index, int property_index);

//  Through analysis control perhaps get_status in control In the news params Set the corresponding properties 
void usr_data_template_property_parse(UtilsJsonValue params);
//  Report all the attributes that need to be reported ,need_report by 1
int usr_data_template_property_report(void* client, char* buf, int buf_len);
//  Report the incident , Here, the user can construct json, More flexibility 
void usr_data_template_event_post(void* client, char* buf, int buf_len, UsrEventIndex id, const char* params);
//  Through analysis action The input parameters in the message set the corresponding properties 
int usr_data_template_action_parse(UtilsJsonValue action_id, UtilsJsonValue params, UsrActionIndex* index);
//  Response to action 
int usr_data_template_action_reply(void* client, char* buf, int buf_len, UsrActionIndex index,
                                   UtilsJsonValue client_token, int code, const char* response);

Downlink data processing

Source code ：data_template_app.c

Downlink data mainly includes ：

1. control news ： Set the property value in the callback , Then read the attribute value for processing
   1. method_control_callback->usr_data_template_property_parse->usr_data_template_property_value_get
2. action news ： Set the input parameter attribute value in the callback , Then read the attribute value for processing
   1. method_action_callback->usr_data_template_action_parse->usr_data_template_action_input_value_get
3. get_status news ： Set... In callback control The attribute value of the message , Then read the attribute value for processing
   1. method_get_status_reply_callback->usr_data_template_property_parse->usr_data_template_property_value_get
4. Reply to various messages ：
   1. If you need to implement QOS1 quality , Please establish a queue implementation in the application layer （ It depends on the business , Different business requirements have different requirements for retransmission and timeout time , Typical examples are summarized based on business experience ）.
   2. If it is QOS0 quality , All replies can be ignored directly （ Most data collection messages can be handled this way ）.

Uplink data reporting

Source code ：data_template_app.c

The online data mainly includes ：

1. report news ： Setting property values （need_reoprt Set as 1）, Then call the interface to report all need_report by 1 Properties of
   1. usr_data_template_property_value_set->usr_data_template_property_report
2. control_reply news ： Call the interface in the callback to reply directly , It's OK not to reply , It depends on the business
   1. method_control_callback->IOT_DataTemplate_PropertyControlReply
3. action_reply news ： Reply according to the result in the call , Because of the clouds API There is a timeout limit , So the reply must be immediate , If you can't complete the action , Please reply by attribute reporting .
   1. method_action_callback->usr_data_template_action_reply
4. event Report ： Call interface , To remodel oneself json Report ,sdk Examples are provided in . This is more flexible and simple
   1. usr_data_template_event_post

matters needing attention

The method provided in this paper is designed to summarize the previous business , There are the following restrictions , Please modify according to the business ：

1. By default, all attributes are passed usr_data_template_property_value_set It will be set after setting need_report by 1, And in the call usr_data_template_property_report I'll report it later . If you do not need to report the attribute , You can filter by attribute index .
2. usr_data_template_property_parse Can parse json And set all the properties , If multiple attributes are required to take effect together , Please integrate these attributes into the structure or string type , Or modify the implementation of the interface , Judge against the index .
3. All replies will not be processed , For some special scenes （ Weak net ）, The application layer implements QOS1, At present, there are few project demands .