SimDatabase

A MySQL/WebAPI(JSON) extension for Simulink.

MySQL block

The MySQL database block connects to a MySQL server in order to request the desired output data, this is achieved by a custom CMEX S-Function written in C using the MySQL Connector C API version 6.1.11.

The block can interpret a predefined format of SQL entry:

date	time	data
YYYY-MM-DD	hh:mm:ss	N1=v1;N2=v2;N3=v3; …
...	...	...

This way a specified number of vs can be extracted from the database for the given Ns based on the time interval.

The precision required for the simulation is, currently, achieved by linear interpolation, which can be turned off.

The connection and the query take a long time compared to the other operations. To solve this problem the block saves the results in a unique file and only uses the database when this file does not exist, otherwise reads the data from the file, which takes significantly less time.

WebAPI (JSON) block

The WebAPI (JSON) block connects to a TCP/IP server in order to request the desired output data in the form of a JSON response. The block implements a TCP/IP client and uses DaveGamble's cJSON library to parse the response.

An example of a request:

http://127.0.0.1/api/api.php?startDate=2019-05-
17&startTime=06:00:00&endDate=2019-05-
17&endTime=20:30:00&sensors=TW,I

An example of a response (if the query was successful):

{
    "data":[
        {
            "date":"2018-04-17",
            "time":"06:00:00",
            "TW":20.98,
            "I":53.33
        },
        {
            "date":"2018-04-17",
            "time":"06:40:00",
            "TW":21.95,
            "I":103.33
        }
    ]
}

An example of a response (if the query was unsuccessful):

{
    "error": "startTime is needed"
}

The precision required for the simulation is, currently, achieved by linear interpolation, which can be turned off.

The connection and the query take a long time compared to the other operations. To solve this problem the block saves the results in a unique file and only uses the database when this file does not exist, otherwise reads the data from the file, which takes significantly less time.

Requirements

• MATLAB (>= R2018b) + Simulink (trial can do the trick)
• Visual Studio 2017 Community Edition (free)

Compilation

Setup mex with the mex -setup command in MATLAB. Run sfun/sql/compile.m or sfun/webjson/compile.m.

Usage

Use the database example example/sql/sim_test.sql to setup the database. In order to use the JSON block, an example implementation of the API can be found in example/webjson, it is called api. It uses the previously installed database scheme.

Notes

• Compiled with MS Visual Studio 2017 Community.
• Tested on Windows 10 x64.