`timescale 1ns / 1ps
module ADC_peripheral(  clk, reset, ADC_EOC, ADC_CS, ADC_CSTART,
                        ADC_SCLK,  ADC_SDIN, ADC_SDOUT, we2, 
                        rdBus2, wrBus2, addr2);
                        			
    input   clk, reset, ADC_EOC;
    input   [7:0] rdBus2;
    output  we2, ADC_CS, ADC_CSTART, ADC_SCLK;
    output  [7:0]   wrBus2;
    output  [8:0]   addr2;
    inout   ADC_SDIN, ADC_SDOUT; 

    reg  we2=0, nSample=0;
    reg  [7:0]   wrBus2;
    reg  [8:0]   addr2;
    reg  [7:0]   auto_count=0;
    reg  [4:0]   w_st2=0;
    reg  [3:0]   SPI_in_data=0;
    reg  [9:0]   SPI_out_data;
    reg  SPI_rd = 0;
    reg  SPI_wr = 0;
    reg  [7:0]   buffer_rd1; 
    reg  [3:0]   ADC_cmd;
    
    assign ADC_CSTART = 1'b1;

    // SPI comunication module instantiation
    reg ADC_SCLK_buffer = 0;
    reg ADC_SDIN_buffer = 0;
    reg busy = 0;

    reg [3:0] in_buffer=0;
    reg [9:0] out_buffer;
    reg [7:0] clkcount = 0;
    reg [7:0] clkdiv = 255;
    reg [4:0] count = 0;

    assign ADC_CS = ~busy;

    always@(SPI_rd or out_buffer or busy or clkdiv)
    begin
        SPI_out_data = 10'bx; 
        if(SPI_rd)
            begin SPI_out_data = out_buffer; end
    end

    always@(negedge clk)
    begin
        if(!busy)
        begin
            if(SPI_wr)
                begin in_buffer = SPI_in_data; busy = 1; end
        end
	    else
	    begin
            clkcount = clkcount + 1;
            if(clkcount >= clkdiv)
            begin
                clkcount = 0;
                // Send the ADC CMD on first 4 rising edge of SCLK
                if((count % 2) == 0)
                begin
                    ADC_SDIN_buffer = in_buffer[3];
                    in_buffer = in_buffer << 1;
                end
                // We generate 10 cicles of SCLK
                if(count > 0 && count < 21)
                begin
                    ADC_SCLK_buffer = ~ADC_SCLK_buffer;
                end
                count = count + 1;
                if(count > 21)
                begin
                    count = 0;
                    busy = 0;
                end
            end
	    end
    end

    always@(posedge ADC_SCLK_buffer)
    begin
        out_buffer = out_buffer << 1;
        out_buffer[0] = ADC_SDOUT;
    end

    assign ADC_SCLK = ADC_SCLK_buffer;
    assign ADC_SDIN = ADC_SDIN_buffer;
      
    // 	State Machine for control ADC comunication
    always @(posedge clk)
    if(reset) 
        {we2, SPI_wr, SPI_rd, w_st2, auto_count, SPI_in_data} <= 0;
    else begin
        case (w_st2)
             0: begin addr2 <= 0; w_st2 <= 1; end
             1: begin 
                    ADC_cmd <= rdBus2[3:0];
                    if (rdBus2[7:4] == 5)
                        // Send command without read samples
                        begin addr2<= 2; w_st2 <= 2; nSample <= 1; end
                    else if (rdBus2[7:4] == 6)
                        // Read: Stop when buffer full
                        begin addr2<= 2; w_st2 <= 2; nSample <= 0; end
                    else if (rdBus2[7:4] == 9)
                        // Set clkdiv on SPI controller
                        begin addr2<= 1; w_st2 <= 10; end 
                    else                      
                        begin w_st2 <= 0; end
                end
		     2: begin
			        if (rdBus2[7:0] == 0)
			            begin auto_count<=0; w_st2 <= 0; end 
			        else begin
				        //Send data to ADC
				        buffer_rd1<=rdBus2; 
				        auto_count<=auto_count+1;
				        SPI_in_data <= ADC_cmd[3:0]; 
				        SPI_wr <= 1; w_st2 <= 3;
			        end
			    end
		     3: begin 
			        SPI_wr <= 0;
			        //Wait for complete convertion
			        if(!ADC_EOC || ADC_CS) begin 
				        buffer_rd1<=buffer_rd1-1;
				        SPI_rd <=1; 
				        if(nSample)	
				            w_st2<= 8; 
				        else
				            w_st2<= 4; 
			        end 
			    end
		     4: begin 
		            //Write data on BRAM  (LOW)
		            wrBus2 <= SPI_out_data[7:0]; 
		            addr2 <= 2+2*auto_count;
				    we2 <= 1; w_st2 <= 5; 
			    end
		     5: begin we2 <= 0; w_st2 <= 6; end	
		     6: begin 
		            //Write data on BRAM  (HI)
		            wrBus2 <= SPI_out_data[9:8]; 
		            addr2 <= 3+2*auto_count; 
				    we2 <= 1; w_st2 <= 7; 
			    end
		     7: begin we2 <= 0; w_st2 <= 8; end	
		     8: begin
                    SPI_rd <=0; 			        
                    //Update Buffer Size value
		            wrBus2 <= buffer_rd1; 
		            addr2 <= 2;
			        we2 <= 1; w_st2 <= 9;    
			    end
		     9: begin we2 <= 0; w_st2 <= 0; end
		        
		        //Sent clock divider for speed on SPI comunication
		    10: begin clkdiv = rdBus2;  w_st2 <= 0; end 			 
        endcase
      end
    endmodule