The problem is very subtle. I used the option --preproc_includes to diagnose it. This option shows you how the include files nest each other. I built Driver_eQEP.c with --preproc_includes and tweaked the resulting .pp file a bit to produce this ...
..\Driver_eQEP.h ..\Config.h C:/ti/controlSUITE/device_support/f28m35x/v201/F28M35x_common/include/DSP28x_Project.h C:/ti/controlSUITE/device_support/f28m35x/v201/F28M35x_headers/include/F28M35x_Device.h C:\ti\controlSUITE\device_support\f28m35x\v201\F28M35x_headers\include\F28M35x_Adc.h // many controlSUITE lines snipped here ..\defines.h ..\Driver_eQEP.h C:/ti_ccs55/ccsv5/tools/compiler/c2000_6.2.0/include/math.h C:/ti_ccs55/ccsv5/tools/compiler/c2000_6.2.0/include/linkage.h ..\main.h ..\Config.h ..\Filters.h ..\Config.h ..\Periph_Config_C28.h // error comes from here!!! ..\Config.h ..\Driver_eQEP.h
When the enumerated type eQEP_Index_Pin_State_Type is seen on line 18 of Periph_Config_C28.h, the #include Driver_eQEP.h from line 8 of Driver_eQEP.c of has not finished processing. The compiler has yet to see the line which defines eQEP_Index_Pin_State_Type. That happens after the processing of Periph_Config_C28.h is complete.
Thanks and regards,
-George