万源归宗：单片机与FPGA演义第一回

只看该作者 · 2010-6-15 14:19

本帖最后由 cll 于 2010-6-16 13:59 编辑

本人是一名电子爱好者，93年用51 2000年学用FPGA及ARM到现在,在这里聊一些经验感想，供大伙解闷.
话说武术最高境界--万源归宗，当代也有一位电子宗师，他用74LS系列做了一台计算机，带MMU,移植了GCC,配操作系统，看官想知道他是谁呢，后文中会一一解说，以此作为开头，单片机与FPGA万源归宗。
第一式：有招胜无招

Bresenham画线算法单片机程序如下：
int BresenhamLine ( int x1 , int y1 , int x2 , int y2 , int c)
{
int dx , dy ;
int tx , ty ;
int inc1 , inc2 ;
int d , iTag ;
int x , y ;
putpixel ( x1 , y1 , c ) ;
if ( x1 == x2 && y1 == y2 )
  return 1 ;
iTag = 0 ;
dx = abs ( x2 - x1 );
dy = abs ( y2 - y1 );
if ( dx < dy )
{
  iTag = 1 ;
  Swap ( & x1 , & y1 );
  Swap ( & x2 , & y2 );
  Swap ( & dx , & dy );
}
tx = ( x2 - x1 ) > 0 ? 1 : -1 ;
ty = ( y2 - y1 ) > 0 ? 1 : -1 ;
x = x1 ;
y = y1 ;
inc1 = 2 * dy ;
inc2 = 2 * ( dy - dx );
d = inc1 - dx ;
while ( x != x2 )
{
  if ( d < 0 )
d += inc1 ;
  else
  {
y += ty ;
d += inc2 ;
  }
  if ( iTag )
putpixel ( y , x , c ) ;
  else
putpixel ( x , y , c ) ;
  x += tx ;
}
return 0;
}
Swap ( int * a , int * b )
{
int tmp ;
tmp = * a ;
* a = * b ;
* b = tmp ;

}

FPGA实现如下verilog HDL :
module line
(
input[31 :0] page_address,
input clk_i,
input rstn_i,
input load_i,
input ack_i,
input signed  [15:0] sx,
input signed  [15:0] sy,
input signed  [15:0] ex,
input signed  [15:0] ey,
input[23:0] f_color_i,
input[23:0] b_color_i,
input[7 :0] data_i,

output[23 :0] data_o,
output[23 :0] addr_o,
output       pset_start_o,
output reg line_over_o
);
reg[23: 0]  addr;
reg[7 :0] rdata_i;
reg signed [15:0] x;
reg signed [15:0] y;
reg signed [15  :0] xsign;
reg signed [15  :0] ysign;

reg signed [16  :0] delta_x;
reg signed [16  :0] delta_y;
reg [16  :0] rdelta_x;
reg [16  :0] rdelta_y;
reg signed [16  :0] i;
reg signed [16  :0] e;
reg  change;
reg [3:0]state;
reg pset_load;
wire  over_o;
// Declare states
parameter S0 = 0, S1 = 1, S2 = 2, S3 = 3,S4 = 4, S5 = 5,S6 =6, S7=7,S40 = 8;
// Determine the next state synchronously, based on the
// current state and the input
always @ (posedge clk_i or negedge rstn_i) begin
  if (! rstn_i)
begin
   line_over_o <= 1'b0;
   rdata_i <= 8'd0;
   addr <= 24'd0;
         xsign <= 16'd0;
         ysign <= 16'd0;
         delta_x <= 17'd0;
         delta_y <= 17'd0;
         i    <= 17'd0;
         e    <= 17'd0;

         pset_load <= 1'b0;
state <= S0;
end
  else
case (state)
S0:
   if(load_i)
   begin
   line_over_o <= 1'b1;

   x    <= sx;
   y    <= sy;
   delta_x <= ex - sx;
   delta_y <= ey - sy;
   state <= S1;
   end
   else
      begin
   line_over_o <= 1'b0;
   state <= S0;
   end
S1:
   begin
   if(delta_x < 0 ) begin rdelta_x <= (~ delta_x )+ 1'b1; xsign<= -1; end
   else          begin rdelta_x <=  delta_x ;       xsign <= 1;  end
   if(delta_y < 0 ) begin rdelta_y <= (~ delta_y )+ 1'b1; ysign <= -1; end
   else          begin rdelta_y <=  delta_y ;       ysign <= 1;  end

   state <= S2;

   end
S2:
   begin
               if(rdelta_x < rdelta_y)
               begin
      delta_x <= rdelta_y;
      delta_y <= rdelta_x;
      change  <= 1'b1;
      end
   else
   begin
      delta_x <= rdelta_x;
      delta_y <= rdelta_y;
      change  <= 1'b0;
   end
   state <= S3;
   end
S3:
   begin
   e       <= ( delta_y * 2 ) - delta_x;
   i       <= 17'd1;
      rdata_i  <= data_i;
   state <= S4;
   end
S4:
   begin
   addr    <=( ( y * 1024 ) + x ) + page_address[23 :0];
   pset_load <= 1'b1;
   state    <= S40;
   end
S40:
   begin
   if(over_o == 1'b1 )
   begin
      pset_load <= 1'b0;
      state <= S5;
   end
   else
      state <= S40;
   end
S5:
   begin
   if( e >= 0 )
   begin
      if(change == 1'b1) x <= x + xsign;
      else             y <= y + ysign;
      e <= e + ( delta_x * 2);
      state <= S5;
   end
   else
      state <= S6;
   end

S6:
   begin
   if( change == 1'b1) y <= y + ysign;
   else                x <= x + xsign;
   e <= e + ( delta_y * 2);
   state <= S7;
   end

S7:
   begin
   if(i < delta_x )
   begin
      i    <= i + 1'b1;
      state <= S4;
   end
   else
   begin
      line_over_o <= 1'b0;
      state <= S0;
   end
   end

endcase
end

endmodule
verilog程序是我做VGA卡的其中的模块.
心中有招,刀剑棍棒皆可用，无论单片机,FPGA或是74LS,本回就此停住。

单片机,dsp ,cpu,都是有限状态机的特例,就数字电路来讲,只是其中的一部分,由此而来,统称的类mcu,cpu等
都有其特定的长处与短处,软件的东西可以硬件做,硬件的东西可以软件模拟,南拳北腿,内外兼修,方能登堂入室
具体的列子在第二式:内外兼修分解。