帮朋友写了个比较简单的SPI MASTER 电路，现在公布源代码，以便初学者学习之用；
1. 源代码
module SPI_MASTER(
input clk , //the FPGA input clock
input rst_n , //the FPGA asynchronous reset
input spi_sdi , //the SPI read input
output reg spi_sdo , //the SPI write output
output reg spi_sck , //the SPI clock
output reg spi_cs //the SPI chip selection
);
//---------------------------------------------
// the following localparam need to configure to
// fit defferent scenarios
//---------------------------------------------
localparam CFG_REG0 = 32'h0123_4567; //the CFG reg0
localparam CFG_REG1 = 32'h5555_5555; //the CFG reg0
localparam CFG_REG2 = 32'hAAAA_AAAA; //the CFG reg0
localparam CNT = 16'd31 ; //the frequncy of spi_sck=clk/(CNT+1);
localparam WR_CTRL = 3'b111 ; //bit0:cfg_reg0 write enable
//bit1:cfg_reg1 write enable
//bit2:cfg_reg2 write enable
localparam RD_CTRL = 3'b111 ; //bit0:cfg_reg0 read enable
//bit1:cfg_reg1 read enable
//bit2:cfg_reg2 read enable
//---------------------------------------------
// the following localparam don't need configuration
//---------------------------------------------
localparam CNT_DIV2 = (CNT>>1) ; //the div clock trun around counter
localparam SPI_IDLE = 3'd0 ;
localparam SPI_TAG = 3'd1 ;
localparam SPI_ADDR = 3'd3 ;
localparam SPI_WDATA = 3'd2 ;
localparam SPI_TURN = 3'd7 ;
localparam SPI_RDATA = 3'd6 ;
//---------------------------------------------
// REG defination
//---------------------------------------------
integer i ;
reg [15:0] clock_cnt ;
reg spi_sck_raw ;
reg [5:0] spi_fsm_ctrl ;
reg [2:0] idx ;
reg [5:0] spi_fsm_start_idx;
reg [3:0] spi_cur_st ;
reg [3:0] spi_next_st ;
reg [4:0] fns_cnt ;
reg [4:0] fns_cnt_next ;
reg [31:0] spi_sdo_raw0 ;
reg [31:0] spi_sdo_raw1 ;
reg [31:0] rback_reg0 ;
reg [31:0] rback_reg1 ;
reg [31:0] rback_reg2 ;
//---------------------------------------------
// WIRE defination
//---------------------------------------------
wire ck_rise ;
wire ck_fall ;
wire ck_jmp ;
wire spi_fsm_start ;
wire spi_fsm_start ;
wire addr_fns ;
wire wdata_fns ;
wire rdata_fns ;
wire trun_fns ;
//---------------------------------------------
// MAIN FUNCTION
//---------------------------------------------
always@(posedge clk or negedge rst_n) begin
if(rst_n==1'b0)
clock_cnt<=16'b0;
else if(spi_next_st!=SPI_IDLE) begin
if(clock_cnt>=CNT)
clock_cnt<=16'b0;
else
clock_cnt<=clock_cnt+1'b1;`
end
else
clock_cnt<=16'b0;
end
//spi clock keep 0 when there is no traction.
assign ck_rise=clock_cnt==CNT ;
assign ck_fall=clock_cnt==CNT_DIV2 ;
assign ck_jmp =ck_rise | ck_fall ;
always@(posedge clk or negedge rst_n) begin
if(rst_n==1'b0)
spi_sck<=1'b0;
else if(spi_cur_st==SPI_IDLE && spi_next_st!=SPI_IDLE || ck_jmp)
spi_sck<=~spi_sck;
else if(spi_cur_st!=SPI_IDLE && spi_next_st==SPI_IDLE)
spi_sck<=1'b0;
end
//chip selection keep 0 when there is no traction.
always@(posedge clk or negedge rst_n) begin
if(rst_n==1'b0)
spi_cs<=1'b0;
else if(spi_next_st==SPI_IDLE)
spi_cs<=1'b0;
else
spi_cs<=1'b1;
end
//the FSM ctrl:ctrl the SPI_FSM to run;
always@(posedge clk or negedge rst_n) begin
if(rst_n==1'b0) begin
spi_fsm_ctrl<={READ_CTRL,WRITE_CTRL};
idx <=3'b0;
end
else if(spi_fsm_ctrl!=6'b0) begin
for(i=5;i>=0;i=i-1) begin
if(spi_fsm_ctrl[i])
idx<=i;
end
if(spi_fsm_done) begin
spi_fsm_ctrl<=spi_fsm_ctrl & (~spi_fsm_start_idx);
end
end
end
assign spi_fsm_start=(spi_fsm_ctrl!=6'b0) && (idx!=3'd0);
always@(*) begin
spi_fsm_start_idx =6'b0;
spi_fsm_start_idx[idx]=1'b1;
end
//the FSM;
always@(posedge clk or negedge rst_n) begin
if(rst_n==1'b0)
spi_cur_st<=SPI_IDLE;
else
spi_cur_st<=spi_next_st;
end
always@(*) begin
spi_next_st=spi_cur_st;
case(spi_cur_st)
SPI_IDLE: if(spi_fsm_start) begin
spi_next_st=SPI_TAG;
end
SPI_TAG : if(ck_rise) begin
spi_next_st=SPI_ADDR;
end
SPI_ADDR: if(ck_rise&&addr_fns) begin
if(spi_fsm_start_idx[2:0]!=3'b0)
spi_next_st=SPI_WDATA;
else
spi_next_st=SPI_TURN;
end
SPI_WDATA:if(ck_rise&&wdata_fns) begin
spi_next_st=SPI_IDLE;
end
SPI_TRUN: if(ck_rise&&turn_fns) begin
spi_next_st=SPI_RDATA;
end
SPI_RDATA:if(ck_rise&&rdata_fns) begin
spi_next_st=SPI_IDLE;
end
endcase
end
always@(*) begin
fns_cnt_next=fns_cnt;
if(spi_cur_st!=spi_next_st)
fns_cnt_next=5'd0;
else if(spi_next_st!=IDLE && ck_rise)
fns_cnt_next=fns_cnt_next+1'b1;
end
always@(posedge clk or negedge rst_n) begin
if(rst_n==1'b0)
fns_cnt<=5'd0;
else
fns_cnt<=fns_cnt_next;
end
assign addr_fns =spi_cur_st==SPI_ADDR & fns_cnt==5'd7 ;
assign wdata_fns=spi_cur_st==SPI_WDATA & fns_cnt==5'd31;
assign rdata_fns=spi_cur_st==SPI_RDATA & fns_cnt==5'd31;
assign turn_fns =spi_cur_st==SPI_TRUN & fns_cnt==5'd1 ;
always@(*) begin
case(spi_fsm_start_idx[2:0])
3'b010 : spi_sdo_raw0=CFG_REG1;
3'b100 : spi_sdo_raw0=CFG_REG2;
default: spi_sdo_raw0=CFG_REG0;
endcase
spi_sdo_raw1=spi_sdo_raw0<<fns_cnt_next;
end
always@(posedge clk or negedge rst_n) begin
if(rst_n==1'b0)
spi_sdo<=1'd0;
else if(spi_next_st=SPI_WDATA)
spi_sdo<=spi_sdo_raw1[31];
else
fns_sdo<=1'b0;
end
//store the read back data to 3 regs;
always@(posedge clk or negedge rst_n) begin
if(rst_n==1'b0) begin
rback_reg0<=32'd0;
rback_reg0<=32'd0;
rback_reg0<=32'd0;
end
else if(spi_cur_st=SPI_RDATA && ck_fall) begin
if(spi_fsm_start_idx[5:3]==3'b001)
rback_reg0<={rback_reg0[30:0],spi_sdi};
if(spi_fsm_start_idx[5:3]==3'b010)
rback_reg1<={rback_reg1[30:0],spi_sdi};
if(spi_fsm_start_idx[5:3]==3'b100)
rback_reg2<={rback_reg2[30:0],spi_sdi};
end
end
endmodule
2.使用方法
使用前需要更改以下CODE：
//---------------------------------------------
// the following localparam need to configure to
// fit defferent scenarios
//---------------------------------------------
localparam CFG_REG0 = 32'h0123_4567; //the CFG reg0
localparam CFG_REG1 = 32'h5555_5555; //the CFG reg0
localparam CFG_REG2 = 32'hAAAA_AAAA; //the CFG reg0
localparam CNT = 16'd31 ; //the frequncy of spi_sck=clk/(CNT+1);
localparam WR_CTRL = 3'b111 ; //bit0:cfg_reg0 write enable
//bit1:cfg_reg1 write enable
//bit2:cfg_reg2 write enable
localparam RD_CTRL = 3'b111 ; //bit0:cfg_reg0 read enable
//bit1:cfg_reg1 read enable
//bit2:cfg_reg2 read enable
- CNT为SPI传输时钟相对模块工作时钟的分频系数；
- CFG_REG0/CFG_REG1/CFG_REG2为要写入slave中3个32bit寄存器的内容；
- WR_CTRL/RD_CTRL控制写入哪些寄存器和读出哪些寄存器；
- 默认的流程为先写后读。
小结
可用其他软件接口代替localparam定义；
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