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GHDL c interfaces and extensions.

1. Based on the example, I created a makefile and changed some of the source code to run in a standalone mode. I have also found this page to be helpful.


2. The example is very simple. The c code is merely driving four variables of std_ulogic type.


3. I modified the c code main function to simply drive constant data, and not from a real parallel port:
   
   
   void lecture_boutons(char boutons[4]) {
     unsigned int u= SULV_0 | (SULV_1 << 8) | (SULV_Z << 16) | (SULV_X << 24);
     *(int*)boutons = u;
   }
   
   I have also created a procedure that has an in variable i.e. data is passed from VHDL to c.
   
   --VHDL
   procedure read_v (v: in std_ulogic);
     attribute foreign of read_v :
       procedure is "VHPIDIRECT read_v";
   
   
   //C
   char glb;
   
   void read_v(char v) {
     glb=v;
   }
   
   -> code



4. The makefile has a few steps. First the c code is compiled, next comes vhdl analysis and last elaboration and execution file.
   Parts of the makefile are shown below:
   
   all : boutons_c.o test_boutons
   
   .PHONY : all
   test_boutons : work-obj93.cf
     $(GG) $(EFLAGS) -Wl,boutons_c.o test_boutons
   
   .PHONY : boutons_c.o
   boutons_c.o : boutons.c
     $(CC) $(CFLAGS) boutons.c -o boutons_c.o
   
   .PHONY : work-obj93.cf
   work-obj93.cf : boutons.vhdl
     $(GG) $(AFLAGS) boutons.vhdl
   
   .PHONY: cleanall
   cleanall :
     $(shell `find . -maxdepth 1 -name "*.o" -exec rm -f {} \;`)
   

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