Current status of tunable parameters

[diegoferigo]

Despite the code generated with Simulink Coder supports tunable parameters, the ones coming from the block masks are not accessible. Refer to the Operation selected from the drop-down menu of the SignalMath block of the example:

blockfactory/example/matlab/AutogenerationExample_grt_rtw/AutogenerationExample.cpp

Lines 104 to 107 in a05e6d0

	params.storeParameter<std::string>(
	"Addition",
	blockfactory::core::ParameterMetadata(
	blockfactory::core::ParameterType::STRING, 2.0, 1.0, 1.0, "Operation"));

In line 105 it is hardcoded, and cannot be changed.

Instead, for what concern parameters that come from the workspace (and constants present in the Simulink Model are analogous), they are stored in a static struct:

blockfactory/example/matlab/AutogenerationExample_grt_rtw/AutogenerationExample.h

Lines 75 to 80 in a05e6d0

	struct P_AutogenerationExample_T_
	{
	real_T Constant_Value[5]; /* Expression: [1 2 3 4 5]
	* Referenced by: '<Root>/Constant'
	*/
	};

blockfactory/example/matlab/AutogenerationExample_grt_rtw/AutogenerationExample.cpp

Lines 390 to 400 in a05e6d0

	AutogenerationExampleModelClass::AutogenerationExampleModelClass()
	{
	static const P_AutogenerationExample_T AutogenerationExample_P_temp = {
	/* Expression: [1 2 3 4 5]
	* Referenced by: '<Root>/Constant'
	*/
	{1.0, 2.0, 3.0, 4.0, 5.0}}; /* Modifiable parameters */
	/* Initialize tunable parameters */
	AutogenerationExample_P = AutogenerationExample_P_temp;
	}

Despite they can be changed during runtime (the symbol is static), it's basically impossible to know what is the index of the parameter you want to access. In this case there's only one, but if there were more, the cpp will contain a curly braces initialization for all of them. It would be great having a way to access these parameters e.g. by name (and I mean string, not name of the variable like P_AutogenerationExample_T_.Constant_Value in this case), but the approach used by the coder does not allow it.

cc @traversaro

[diegoferigo]

Also related to robotology/whole-body-controllers#26

[traversaro]

Are we generating the C API to access the parameters, as described in https://github.com/Kvixen/Simulix#exporting-your-model-from-simulink ? Relevant matlab docs: https://it.mathworks.com/help/rtw/ug/data-interchange-using-the-c-api.html .

[diegoferigo]

I remember I tried them but I had no luck even with them.