Data Interchange Using the C API and External Mode

I need change the parameters during HIL (hardware in the loop) execution without Matlab. I have seen the "Data Interchange Using the C API" but due to my requeriments I can't clear the external mode. When I select both occurs this error:

Error: Simulink Coder does not support both External Mode and the C API at the same time.

Are there any manner to generate a C-file with the information of the parameters that appears in "Data Interchange Using the C API" (rtModelParameters, rtDataAddrMap, rtDataTypeMap, rtDimensionMap, rtFixPtMap) to access them?.

I have seen the files "capilib.tlc" and "capi.tlc" but they are very cumbersome.

Thanks in advance.