FPGA——spi代码篇
一、FPGA 开发SPI基础
为了避免每次SPI驱动重写，直接参数化，尽量一劳永逸。SPI master有啥用呢，你发现各种外围芯片的配置一般都是通过SPI配置的，只不过有三线和四线。SPI slave有什么用呢，当外部主机（cpu）要读取FPGA内部寄存器值，那就很有用了，FPGA寄存器就相当于RAM，cpu通过SPI寻址读写数据。代码仅供参考，勿做商业用途。
二、SPI三线，四线区别
三线制指的是CS，CLK，MOMI，是半双工方式；四线制指的是 CS，CLK，MOSI和MISO，是全双工方式。
三、SPI代码构思
1. SPI salve
1.支持三线SPI或者四线SPI。通过define切换。
2.支持指令长度、帧长自定义。
3.工作时钟可自定义，大于SPI clk的2倍。
用户只需修改：（1）几线SPI。（2）单帧长度。（3）指令长度。（4）寄存器开辟。
注意：指令最高bit表示读写，低写高读，其余bit表示地址。指令接着为数据端，两者位宽之和即为SPI单帧长。
//`define SPI_LINE //是否是三线SPI
`define SPI_FRAME_WIDTH 16 //SPI一帧长度为16
`define SPI_INS_WIDTH 8 //SPI指令长
`timescale 1ns/1ps
module spi_slave
(
input i_clk , //work clk
input i_rst_n ,
input i_spi_clk , //SPI clk
input i_spi_cs , //SPI cs
`ifdef SPI_LINE //条件编译
inout io_spi_sdio
`else
input i_spi_mosi , //SPI mosi
output o_spi_miso //SPI miso
`endif
);
//位宽计算函数
function integer clogb2 (input integer depth);
begin
for (clogb2=0; depth>0; clogb2=clogb2+1)
depth = depth >>1;
end
endfunction
reg r_cs = 1'b1; //打一拍
always @(posedge i_clk)
begin
r_cs <= i_spi_cs;
end
reg [1:0] r_spi_clk_edge = 2'b00; //SPI clk边沿检测
always @(posedge i_clk)
begin
r_spi_clk_edge <= {r_spi_clk_edge[0],i_spi_clk};
end //always
reg [clogb2(`SPI_FRAME_WIDTH-1)-1:0] r_spi_cnt = 'd0;
always @(posedge i_clk)
begin
if (r_cs) //cs为高则归零
r_spi_cnt <= 'd0;
else if (r_spi_clk_edge == 2'b10) //下降沿才计数
r_spi_cnt <= r_spi_cnt + 'd1;
end
指令锁存
reg [`SPI_INS_WIDTH-1:0] r_ins = 'd0;
always @(posedge i_clk)
begin
if ((~r_cs) && (r_spi_clk_edge == 2'b01)) //上升沿锁存数据
begin
if ((r_spi_cnt >= 0) && (r_spi_cnt <= `SPI_INS_WIDTH-1))
`ifdef SPI_LINE //条件编译
r_ins <= {r_ins[`SPI_INS_WIDTH-2:0],io_spi_sdio};
`else
r_ins <= {r_ins[`SPI_INS_WIDTH-2:0],i_spi_mosi};
`endif
end
end
数值写入
reg [`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-1:0] r_data_rx = 'd0;
always @(posedge i_clk)
begin
if ((~r_cs) && (r_spi_clk_edge == 2'b01)) //上升沿锁存数据
begin
if (r_spi_cnt >= `SPI_INS_WIDTH)
`ifdef SPI_LINE
r_data_rx <= {r_data_rx[`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-2:0],io_spi_sdio};
`else
r_data_rx <= {r_data_rx[`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-2:0],i_spi_mosi};
`endif
end
end
用户寄存器定义
reg [`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-1:0] r_reg0 = 'd0;
reg [`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-1:0] r_reg1 = 'd0;
reg [`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-1:0] r_reg2 = 'd0;
reg [`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-1:0] r_reg3 = 'd0;
always @(posedge i_clk,negedge i_rst_n)
begin
if (~i_rst_n)
begin
r_reg0 <= 'd0;
r_reg1 <= 'd0;
r_reg2 <= 'd0;
r_reg3 <= 'd0;
end
else if ((~r_ins[`SPI_INS_WIDTH-1]) && (r_spi_cnt == (`SPI_FRAME_WIDTH-1)) && (~r_cs) && (r_spi_clk_edge == 2'b01))
begin
`ifdef SPI_LINE
case (r_ins[`SPI_INS_WIDTH-2:0])
'd0:begin r_reg0 <= {r_data_rx[`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-2:0],io_spi_sdio}; end
'd1:begin r_reg1 <= {r_data_rx[`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-2:0],io_spi_sdio}; end
'd2:begin r_reg2 <= {r_data_rx[`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-2:0],io_spi_sdio}; end
'd3:begin r_reg3 <= {r_data_rx[`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-2:0],io_spi_sdio}; end
endcase
`else
case (r_ins[`SPI_INS_WIDTH-2:0])
'd0:begin r_reg0 <= {r_data_rx[`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-2:0],i_spi_mosi}; end
'd1:begin r_reg1 <= {r_data_rx[`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-2:0],i_spi_mosi}; end
'd2:begin r_reg2 <= {r_data_rx[`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-2:0],i_spi_mosi}; end
'd3:begin r_reg3 <= {r_data_rx[`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-2:0],i_spi_mosi}; end
endcase
`endif
end
end
寄存器值读出
reg [`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-1:0] r_data_tx = 'd0;
always @(posedge i_clk)
begin
if (r_ins[`SPI_INS_WIDTH-1] && (~r_cs) && (r_spi_clk_edge == 2'b10))
begin
if (r_spi_cnt == (`SPI_INS_WIDTH-1))
begin
case (r_ins[`SPI_INS_WIDTH-2:0])
'd0:begin r_data_tx <= r_reg0; end
'd1:begin r_data_tx <= r_reg1; end
'd2:begin r_data_tx <= r_reg2; end
'd3:begin r_data_tx <= r_reg3; end
endcase
end
else
r_data_tx <= {r_data_tx[`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-2:0],1'b0};
end
end
读取输出
`ifdef SPI_LINE
assign io_spi_sdio = (r_ins[`SPI_INS_WIDTH-1]) ? (((r_spi_cnt>=`SPI_INS_WIDTH) && (r_spi_cnt<`SPI_FRAME_WIDTH)) ? r_data_tx[`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-1] : 1'bz) : 1'bz;
`else
assign o_spi_miso = ((r_spi_cnt>=`SPI_INS_WIDTH) && (r_spi_cnt<`SPI_FRAME_WIDTH)) ? r_data_tx[`SPI_FRAME_WIDTH-`SPI_INS_WIDTH-1] : 1'b0;
`endif
endmodule // end the spi_slave model2.SPI master
spi master内部仅仅封装SPI驱动，写入值读出控制由上层控制，这部分逻辑很simple，不赘述。用户只需给入SPI帧及控制使能即可。
用户只需修改parameter参数：（1）单帧长；（2）指令长；（3）数据长；（4）工作时钟；（5）SPI clk。
实现不使用状态机，采用线性序列计数法。
//`define SPI_LINE //是否是三线SPI
`timescale 1ns/1ps
module spi_master
#(parameter p_spi_frame_width = 16, //SPI单帧长度
parameter p_spi_ins_width = 8 , //指令长度
parameter p_spi_data_width = 8 //读出数据长度
)
(
input i_clk , //系统时钟
input i_rst_n ,
input i_flag , //检测到flag的上升沿则启动一次传输,一个时钟周期即可
input [p_spi_frame_width-1:0] i_spi_data ,
output o_spi_cs ,
output o_spi_clk ,
`ifdef SPI_LINE //条件编译
inout io_spi_sdio ,
`else
input i_spi_miso , //SPI miso
output o_spi_mosi , //SPI mosi
`endif
output o_transfer_done , //单次传输完成
output [p_spi_data_width-1:0] o_spi_data //读取数据
);
parameter p_clk_fre = 200; //XXM时钟频率
parameter p_spi_clk_fre = 0.5*1000; //SPI 时钟速率,表示1M
parameter p_clk_div = p_clk_fre * 1000/p_spi_clk_fre/2-1;
parameter p_spi_cnt_max = p_spi_frame_width*2-1;
parameter p_spi_ins_max = p_spi_ins_width*2-1;
//位宽计算函数
function integer clogb2 (input integer depth);
begin
for (clogb2=0; depth>0; clogb2=clogb2+1)
depth = depth >>1;
end
endfunction
//把最大值赋值给线型，直接用p_clk_div仿真有问题，但实际上板是可以的
wire [clogb2(p_clk_div)-1:0] w_clk_div;
assign w_clk_div = p_clk_div;
时钟分频
reg [clogb2(p_clk_div)-1:0] r_cnt_div = 'd0;
always @(posedge i_clk)
begin
if (r_cnt_div == w_clk_div)
r_cnt_div <= 'd0;
else
r_cnt_div <= r_cnt_div + 'd1;
end //always
wire w_clk_en; //分频时钟使能
assign w_clk_en = (r_cnt_div == w_clk_div) ? 1'b1 : 1'b0;
reg [1:0] r_flag_edge = 2'b00;
reg [clogb2(p_spi_cnt_max)-1:0] r_spi_cnt = 'd0;
always @(posedge i_clk) //flag边沿检测
begin
r_flag_edge <= {r_flag_edge[0],i_flag};
end
//flag信号展宽到低速时钟域
reg r_flag_enlarge = 1'b0;
always @(posedge i_clk)
begin
if (r_flag_edge == 2'b01) //上升沿拉高
r_flag_enlarge <= 1'b1;
else if (r_spi_cnt == p_spi_ins_max) //足够长的高电平才拉低
r_flag_enlarge <= 1'b0;
end
reg [1:0] r_flag_enlarge_edge = 2'b00;
always @(posedge i_clk)
begin
if (w_clk_en)
r_flag_enlarge_edge <= {r_flag_enlarge_edge[0],r_flag_enlarge};
end
reg r_cs = 1'b1;
always @(posedge i_clk)
begin
if (w_clk_en)
begin
if (r_flag_enlarge_edge == 2'b01) //检测到需要进行SPI操作
r_cs <= 1'b0;
else if (r_spi_cnt == p_spi_cnt_max) //计数到最大值表示一次SPI完成
r_cs <= 1'b1;
end
end
always @(posedge i_clk)
begin
if (w_clk_en)
begin
if(~r_cs) //在操作区间计数
r_spi_cnt <= r_spi_cnt + 'd1;
else
r_spi_cnt <= 'd0;
end
end
数据传输段
reg [p_spi_frame_width-1:0] r_data = 'd0;
always @(posedge i_clk)
begin
if (w_clk_en)
begin
if (r_flag_enlarge_edge == 2'b01) //上升沿刷入
r_data <= i_spi_data;
else if (r_spi_cnt[0] == 1'b1) //数据移动
r_data <= {r_data[p_spi_frame_width-2:0],1'b1};
end
end
数据读取段
reg [p_spi_data_width-1:0] r_data_read = 'd0;
always @(posedge i_clk)
begin
if (w_clk_en)
begin
if (i_spi_data[p_spi_frame_width-1] && (r_spi_cnt > p_spi_ins_max) && (r_spi_cnt[0] == 1'b0)) //是读
`ifdef SPI_LINE
r_data_read <= {r_data_read[p_spi_data_width-2:0],io_spi_sdio};
`else
r_data_read <= {r_data_read[p_spi_data_width-2:0],i_spi_miso};
`endif
end
end
SPI输出段
assign o_spi_cs = r_cs;
assign o_spi_clk = r_cs ? 1'b0 : r_spi_cnt[0];
SPI SDIO的输入输出切换
`ifdef SPI_LINE
assign io_spi_sdio = (i_spi_data[p_spi_frame_width-1]) ? (((r_spi_cnt >= 'd0) && (r_spi_cnt <= p_spi_ins_max)) ? r_data[p_spi_frame_width-1] : 1'bz ) : r_data[p_spi_frame_width-1];
`else
assign o_spi_mosi = r_data[p_spi_frame_width-1];
`endif
assign o_transfer_done = ((~r_cs) && (r_spi_cnt == p_spi_cnt_max)) ? 1'b1:1'b0;
assign o_spi_data = r_data_read;
endmodule // end the spi_master model3.前仿真代码
`define DATA 8'ha5
//`define SPI_LINE
timeunit 1ns;
timeprecision 1ps;
module top;
parameter p_sim_end_time = 1000000; //ns
logic l_clk = 1'b0;
always #2.5 l_clk = ~l_clk;
复位
logic l_rst_n = 1'b0;
initial begin
#100 l_rst_n = 1'b1;
end
wire io_sdio;
wire o_spi_cs;
wire o_spi_clk;
wire o_transfer_done;
wire [7:0] o_spi_data;
多个数据操作模式
reg r_flag = 1'b0;
reg [1:0] r_first_cnt = 2'b00;
always @(posedge l_clk,negedge l_rst_n)
begin
if (~l_rst_n)
r_first_cnt <= 2'b00;
else if (r_first_cnt == 2'd3)
r_first_cnt <= r_first_cnt;
else
r_first_cnt <= r_first_cnt + 2'd1;
end
reg [1:0] r_transfer_done_edge = 2'b00;
always @(posedge l_clk)
begin
r_transfer_done_edge <= {r_transfer_done_edge[0],o_transfer_done};
end
reg [3:0] r_transfer_cnt = 4'd0;
always @(posedge l_clk)
begin
if ((r_first_cnt == 2'd2) && (r_transfer_cnt < `TRANSFER_NUMBER))
r_flag <= 1'b1;
else if ((r_transfer_done_edge == 2'b10) && (r_transfer_cnt < `TRANSFER_NUMBER-1))
r_flag <= 1'b1;
else
r_flag <= 1'b0;
end
always @(posedge l_clk)
begin
if (r_transfer_done_edge == 2'b10)
r_transfer_cnt <= r_transfer_cnt + 'd1;
end
reg [15:0] r_in_data = 16'd0;
always @(*)
begin
if (~l_rst_n) //仿真不执行此段仿真会有问题
r_in_data = 16'h0000;
else
begin
case(r_transfer_cnt)
4'd0:begin r_in_data = {8'h00,8'h43}; end
4'd1:begin r_in_data = 16'h0132; end
4'd2:begin r_in_data = 16'h0245; end
4'd3:begin r_in_data = 16'h0367; end
4'd4:begin r_in_data = 16'h8000; end
4'd5:begin r_in_data = 16'h8100; end
4'd6:begin r_in_data = 16'h8200; end
4'd7:begin r_in_data = 16'h8300; end
default:begin r_in_data = 16'h0000; end
endcase
end
end
wire w_spi_miso;
wire w_spi_mosi;
spi_master inst_spi_master (
.i_clk (l_clk),
.i_rst_n (),
.i_flag (r_flag),
.i_spi_data (r_in_data),
.o_spi_cs (o_spi_cs),
.o_spi_clk (o_spi_clk),
`ifdef SPI_LINE
.io_spi_sdio (io_sdio),
`else
.i_spi_miso (w_spi_miso),
.o_spi_mosi (w_spi_mosi),
`endif
.o_transfer_done (o_transfer_done),
.o_spi_data (o_spi_data)
);
spi_slave inst_spi_slave (
.i_clk (l_clk),
.i_rst_n (l_rst_n),
.i_spi_clk (o_spi_clk),
.i_spi_cs (o_spi_cs),
`ifdef SPI_LINE
.io_spi_sdio (io_sdio)
`else
.i_spi_mosi (w_spi_mosi),
.o_spi_miso (w_spi_miso)
`endif
);
initial begin
#p_sim_end_time $stop;
end
endmodule