fmi4c is a C library that enables import of Functional Mockup Units (FMUs) from FMI 1.0, FMI 2.0 and FMI 3.0.

All kinds of FMUs (model exchange, co-simulation and scheduled execution) are supported.

The library is intended to be lightweight, easy to implement and to have an intuitive interface.

Features

• Import FMUs for FMI 1.0 (co-simulation and model exchange)
• Import FMUs for FMI 2.0 (co-simulation and model exchange)
• Import FMUs for FMI 3.0 (co-simulation, model exchange and scheduled execution)
• Placeholder functions for all API functions, to prevent crash when calling functions not available in FMU

Third Party Dependencies

Dependencies have been chosen to minimize implementation effort and to make the code easy to understand.

• ezxml
• zlib (optional)
• minizip (optional)

API Example

Below is a simplified example on how to load and simulate an FMI 3.0 FMU for co-simulation. More detailed examples are available in the source code for the test executable.

#include <stdio.h>
#include "fmi4c.h"

int main(int argc, char *argv[])
{
    if(argc < 2) {
        printf("Too few arguments.\n");
        exit(1);
    }

    fmiHandle *fmu = loadFmu(fmuPath, "myfmu");

    if(!fmu) {
        printf("Failed to load FMU\n");
        exit(1);
    }

    if(getFmiVersion(fmu) == fmiVersion3 && fmi3SupportsCoSimulation(fmu)) {
        if(!fmi3InstantiateCoSimulation(fmu, ...)) {
            printf("Failed to instantiate FMU\n");
            exit(1);
        }
        fmi3Status status;
        status = fmi3EnterInitializationMode(fmu, ...);
        if(status != fmi3OK) {
            printf("Enter initialization mode failed\n");
            exit(1);
        }
        status = fmi3ExitInitializationMode(fmu);

        double tstart = 0;
        double tend = 1;
        double stepsize = 0.001;
        for(double time=tstart; time <= tend; time+=stepsize) {
            status = fmi3SetFloat64(fmu, ...);
            status = fmi3DoStep(fmu, time, stepsize, ...);
            status = fmi3GetFloat64(fmu, ...);
        }
      
        status = fmi3Terminate(fmu);
        fmi3FreeInstance(fmu);
    }
    
    return 0;
}