1 IIC通信协议简介
IIC通信协议基础知识学习：硬件设计基础----通信协议IIC
2 实验任务
设计IIC驱动模块，并进行仿真验证，观察仿真波形
3 实验设计
3.1 创建工程
新建工程，操作如图所示：
输入工程名和路径，如图：
选择创建RTL工程，如图：
直接点击Next：
继续点击Next：
添加芯片型号，操作如图：
工程创建完成：
3.2 设计输入
创建工程文件，操作如图所示：
创建iic_drive文件：
创建完成：
双击打开，输入代码如下：
module iic_drive(
//系统接口
input clk, //时钟信号，50MHZ
input rst_n, //复位信号，低电平有效
//IIC时序控制接口
input i2c_exec , //IIC触发执行信号
input bit_ctrl , //字地址位控制(16b/8b)
input i2c_rh_wl , //IIC读写控制信号
input [15:0] i2c_addr , //IIC器件内地址
input [ 7:0] i2c_data_w , //IIC要写的数据
output reg [ 7:0] i2c_data_r , //IIC读出的数据
output reg i2c_done , //IIC一次操作完成
output reg i2c_ack , //IIC应答标志 0:应答 1:未应答
//IIC物理接口
output reg scl , //IIC的SCL时钟信号
inout sda , //IIC的SDA信号
//user interface
output reg dri_clk //驱动IIC操作的驱动时钟
);
parameter SLAVE_ADDR = 7'b1010000 ; //IIC从机地址
parameter CLK_FREQ = 26'd50_000_000; //模块输入的时钟频率
parameter I2C_FREQ = 18'd250_000; //IIC_SCL的时钟频率 ,250k
//状态机定义
localparam st_idle = 8'b0000_0001; //空闲状态
localparam st_sladdr = 8'b0000_0010; //发送器件地址(slave address)
localparam st_addr16 = 8'b0000_0100; //发送16位字地址
localparam st_addr8 = 8'b0000_1000; //发送8位字地址
localparam st_data_wr = 8'b0001_0000; //写数据(8 bit)
localparam st_addr_rd = 8'b0010_0000; //发送器件地址读
localparam st_data_rd = 8'b0100_0000; //读数据(8 bit)
localparam st_stop = 8'b1000_0000; //结束IIC操作
//reg 定义
reg sda_dir ; //IIC数据(SDA)方向控制
reg sda_out ; //SDA输出信号
reg st_done ; //状态结束
reg wr_flag ; //写标志
reg [ 6:0] cnt ; //计数
reg [ 7:0] cur_state ; //状态机当前状态
reg [ 7:0] next_state; //状态机下一状态
reg [15:0] addr_t ; //地址
reg [ 7:0] data_r ; //读取的数据
reg [ 7:0] data_wr_t ; //IIC需写的数据的临时寄存
reg [ 9:0] clk_cnt ; //分频时钟计数
//wire 定义
wire sda_in ; //SDA输入信号
wire [8:0] clk_divide ; //模块驱动时钟的分频系数
//SDA控制
assign sda = sda_dir ? sda_out : 1'bz ; //SDA数据输出或高阻
assign sda_in = sda ; //SDA数据输入
assign clk_divide = (CLK_FREQ/I2C_FREQ) >> 2'd2 ; //模块驱动时钟的分频系数
//生成IIC的SCL的四倍频率的驱动时钟用于驱动IIC的操作
always @(posedge clk or negedge rst_n) begin
if(!rst_n) begin
dri_clk <= 1'b0;
clk_cnt <= 10'd0;
end
else if(clk_cnt == clk_divide[8:1] - 1'd1) begin
clk_cnt <= 10'd0;
dri_clk <= ~dri_clk;
end
else
clk_cnt <= clk_cnt + 1'b1;
end
//(三段式状态机)同步时序描述状态转移
always @(posedge dri_clk or negedge rst_n) begin
if(!rst_n)
cur_state <= st_idle;
else
cur_state <= next_state;
end
//组合逻辑判断状态转移条件
always @(*) begin
next_state = st_idle;
case(cur_state)
st_idle: begin //空闲状态
if(i2c_exec) begin
next_state = st_sladdr;
end
else
next_state = st_idle;
end
st_sladdr: begin
if(st_done) begin
if(bit_ctrl) //判断是16位还是8位字地址
next_state = st_addr16;
else
next_state = st_addr8 ;
end
else
next_state = st_sladdr;
end
st_addr16: begin //写16位字地址
if(st_done) begin
next_state = st_addr8;
end
else begin
next_state = st_addr16;
end
end
st_addr8: begin //8位字地址
if(st_done) begin
if(wr_flag==1'b0) //读写判断
next_state = st_data_wr;
else
next_state = st_addr_rd;
end
else begin
next_state = st_addr8;
end
end
st_data_wr: begin //写数据(8 bit)
if(st_done)
next_state = st_stop;
else
next_state = st_data_wr;
end
st_addr_rd: begin //写地址以进行读数据
if(st_done) begin
next_state = st_data_rd;
end
else begin
next_state = st_addr_rd;
end
end
st_data_rd: begin //读取数据(8 bit)
if(st_done)
next_state = st_stop;
else
next_state = st_data_rd;
end
st_stop: begin //结束I2C操作
if(st_done)
next_state = st_idle;
else
next_state = st_stop ;
end
default: next_state= st_idle;
endcase
end
//时序电路描述状态输出
always @(posedge dri_clk or negedge rst_n) begin
//复位初始化
if(!rst_n) begin
scl <= 1'b1;
sda_out <= 1'b1;
sda_dir <= 1'b1;
i2c_done <= 1'b0;
i2c_ack <= 1'b0;
cnt <= 1'b0;
st_done <= 1'b0;
data_r <= 1'b0;
i2c_data_r<= 1'b0;
wr_flag <= 1'b0;
addr_t <= 1'b0;
data_wr_t <= 1'b0;
end
else begin
st_done <= 1'b0 ;
cnt <= cnt +1'b1 ;
case(cur_state)
st_idle: begin //空闲状态
scl <= 1'b1;
sda_out <= 1'b1;
sda_dir <= 1'b1;
i2c_done<= 1'b0;
cnt <= 7'b0;
if(i2c_exec) begin
wr_flag <= i2c_rh_wl ;
addr_t <= i2c_addr ;
data_wr_t <= i2c_data_w;
i2c_ack <= 1'b0;
end
end
st_sladdr: begin //写地址(器件地址和字地址)
case(cnt)
7'd1 : sda_out <= 1'b0; //开始IIC
7'd3 : scl <= 1'b0;
7'd4 : sda_out <= SLAVE_ADDR[6]; //传送器件地址
7'd5 : scl <= 1'b1;
7'd7 : scl <= 1'b0;
7'd8 : sda_out <= SLAVE_ADDR[5];
7'd9 : scl <= 1'b1;
7'd11: scl <= 1'b0;
7'd12: sda_out <= SLAVE_ADDR[4];
7'd13: scl <= 1'b1;
7'd15: scl <= 1'b0;
7'd16: sda_out <= SLAVE_ADDR[3];
7'd17: scl <= 1'b1;
7'd19: scl <= 1'b0;
7'd20: sda_out <= SLAVE_ADDR[2];
7'd21: scl <= 1'b1;
7'd23: scl <= 1'b0;
7'd24: sda_out <= SLAVE_ADDR[1];
7'd25: scl <= 1'b1;
7'd27: scl <= 1'b0;
7'd28: sda_out <= SLAVE_ADDR[0];
7'd29: scl <= 1'b1;
7'd31: scl <= 1'b0;
7'd32: sda_out <= 1'b0; //0:写
7'd33: scl <= 1'b1;
7'd35: scl <= 1'b0;
7'd36: begin
sda_dir <= 1'b0;
sda_out <= 1'b1;
end
7'd37: scl <= 1'b1;
7'd38: begin //从机应答
st_done <= 1'b1;
if(sda_in == 1'b1) //高电平表示未应答
i2c_ack <= 1'b1; //拉高应答标志位
end
7'd39: begin
scl <= 1'b0;
cnt <= 1'b0;
end
default : ;
endcase
end
st_addr16: begin
case(cnt)
7'd0 : begin
sda_dir <= 1'b1 ;
sda_out <= addr_t[15]; //传送字地址
end
7'd1 : scl <= 1'b1;
7'd3 : scl <= 1'b0;
7'd4 : sda_out <= addr_t[14];
7'd5 : scl <= 1'b1;
7'd7 : scl <= 1'b0;
7'd8 : sda_out <= addr_t[13];
7'd9 : scl <= 1'b1;
7'd11: scl <= 1'b0;
7'd12: sda_out <= addr_t[12];
7'd13: scl <= 1'b1;
7'd15: scl <= 1'b0;
7'd16: sda_out <= addr_t[11];
7'd17: scl <= 1'b1;
7'd19: scl <= 1'b0;
7'd20: sda_out <= addr_t[10];
7'd21: scl <= 1'b1;
7'd23: scl <= 1'b0;
7'd24: sda_out <= addr_t[9];
7'd25: scl <= 1'b1;
7'd27: scl <= 1'b0;
7'd28: sda_out <= addr_t[8];
7'd29: scl <= 1'b1;
7'd31: scl <= 1'b0;
7'd32: begin
sda_dir <= 1'b0;
sda_out <= 1'b1;
end
7'd33: scl <= 1'b1;
7'd34: begin //从机应答
st_done <= 1'b1;
if(sda_in == 1'b1) //高电平表示未应答
i2c_ack <= 1'b1; //拉高应答标志位
end
7'd35: begin
scl <= 1'b0;
cnt <= 1'b0;
end
default : ;
endcase
end
st_addr8: begin
case(cnt)
7'd0: begin
sda_dir <= 1'b1 ;
sda_out <= addr_t[7]; //字地址
end
7'd1 : scl <= 1'b1;
7'd3 : scl <= 1'b0;
7'd4 : sda_out <= addr_t[6];
7'd5 : scl <= 1'b1;
7'd7 : scl <= 1'b0;
7'd8 : sda_out <= addr_t[5];
7'd9 : scl <= 1'b1;
7'd11: scl <= 1'b0;
7'd12: sda_out <= addr_t[4];
7'd13: scl <= 1'b1;
7'd15: scl <= 1'b0;
7'd16: sda_out <= addr_t[3];
7'd17: scl <= 1'b1;
7'd19: scl <= 1'b0;
7'd20: sda_out <= addr_t[2];
7'd21: scl <= 1'b1;
7'd23: scl <= 1'b0;
7'd24: sda_out <= addr_t[1];
7'd25: scl <= 1'b1;
7'd27: scl <= 1'b0;
7'd28: sda_out <= addr_t[0];
7'd29: scl <= 1'b1;
7'd31: scl <= 1'b0;
7'd32: begin
sda_dir <= 1'b0;
sda_out <= 1'b1;
end
7'd33: scl <= 1'b1;
7'd34: begin //从机应答
st_done <= 1'b1;
if(sda_in == 1'b1) //高电平表示未应答
i2c_ack <= 1'b1; //拉高应答标志位
end
7'd35: begin
scl <= 1'b0;
cnt <= 1'b0;
end
default : ;
endcase
end
st_data_wr: begin //写数据(8 bit)
case(cnt)
7'd0: begin
sda_out <= data_wr_t[7]; //IIC写8位数据
sda_dir <= 1'b1;
end
7'd1 : scl <= 1'b1;
7'd3 : scl <= 1'b0;
7'd4 : sda_out <= data_wr_t[6];
7'd5 : scl <= 1'b1;
7'd7 : scl <= 1'b0;
7'd8 : sda_out <= data_wr_t[5];
7'd9 : scl <= 1'b1;
7'd11: scl <= 1'b0;
7'd12: sda_out <= data_wr_t[4];
7'd13: scl <= 1'b1;
7'd15: scl <= 1'b0;
7'd16: sda_out <= data_wr_t[3];
7'd17: scl <= 1'b1;
7'd19: scl <= 1'b0;
7'd20: sda_out <= data_wr_t[2];
7'd21: scl <= 1'b1;
7'd23: scl <= 1'b0;
7'd24: sda_out <= data_wr_t[1];
7'd25: scl <= 1'b1;
7'd27: scl <= 1'b0;
7'd28: sda_out <= data_wr_t[0];
7'd29: scl <= 1'b1;
7'd31: scl <= 1'b0;
7'd32: begin
sda_dir <= 1'b0;
sda_out <= 1'b1;
end
7'd33: scl <= 1'b1;
7'd34: begin //从机应答
st_done <= 1'b1;
if(sda_in == 1'b1) //高电平表示未应答
i2c_ack <= 1'b1; //拉高应答标志位
end
7'd35: begin
scl <= 1'b0;
cnt <= 1'b0;
end
default : ;
endcase
end
st_addr_rd: begin //写地址以进行读数据
case(cnt)
7'd0 : begin
sda_dir <= 1'b1;
sda_out <= 1'b1;
end
7'd1 : scl <= 1'b1;
7'd2 : sda_out <= 1'b0; //重新开始
7'd3 : scl <= 1'b0;
7'd4 : sda_out <= SLAVE_ADDR[6]; //传送器件地址
7'd5 : scl <= 1'b1;
7'd7 : scl <= 1'b0;
7'd8 : sda_out <= SLAVE_ADDR[5];
7'd9 : scl <= 1'b1;
7'd11: scl <= 1'b0;
7'd12: sda_out <= SLAVE_ADDR[4];
7'd13: scl <= 1'b1;
7'd15: scl <= 1'b0;
7'd16: sda_out <= SLAVE_ADDR[3];
7'd17: scl <= 1'b1;
7'd19: scl <= 1'b0;
7'd20: sda_out <= SLAVE_ADDR[2];
7'd21: scl <= 1'b1;
7'd23: scl <= 1'b0;
7'd24: sda_out <= SLAVE_ADDR[1];
7'd25: scl <= 1'b1;
7'd27: scl <= 1'b0;
7'd28: sda_out <= SLAVE_ADDR[0];
7'd29: scl <= 1'b1;
7'd31: scl <= 1'b0;
7'd32: sda_out <= 1'b1; //1:读
7'd33: scl <= 1'b1;
7'd35: scl <= 1'b0;
7'd36: begin
sda_dir <= 1'b0;
sda_out <= 1'b1;
end
7'd37: scl <= 1'b1;
7'd38: begin //从机应答
st_done <= 1'b1;
if(sda_in == 1'b1) //高电平表示未应答
i2c_ack <= 1'b1; //拉高应答标志位
end
7'd39: begin
scl <= 1'b0;
cnt <= 1'b0;
end
default : ;
endcase
end
st_data_rd: begin //读取数据(8 bit)
case(cnt)
7'd0: sda_dir <= 1'b0;
7'd1: begin
data_r[7] <= sda_in;
scl <= 1'b1;
end
7'd3: scl <= 1'b0;
7'd5: begin
data_r[6] <= sda_in ;
scl <= 1'b1 ;
end
7'd7: scl <= 1'b0;
7'd9: begin
data_r[5] <= sda_in;
scl <= 1'b1 ;
end
7'd11: scl <= 1'b0;
7'd13: begin
data_r[4] <= sda_in;
scl <= 1'b1 ;
end
7'd15: scl <= 1'b0;
7'd17: begin
data_r[3] <= sda_in;
scl <= 1'b1 ;
end
7'd19: scl <= 1'b0;
7'd21: begin
data_r[2] <= sda_in;
scl <= 1'b1 ;
end
7'd23: scl <= 1'b0;
7'd25: begin
data_r[1] <= sda_in;
scl <= 1'b1 ;
end
7'd27: scl <= 1'b0;
7'd29: begin
data_r[0] <= sda_in;
scl <= 1'b1 ;
end
7'd31: scl <= 1'b0;
7'd32: begin
sda_dir <= 1'b1;
sda_out <= 1'b1;
end
7'd33: scl <= 1'b1;
7'd34: st_done <= 1'b1; //非应答
7'd35: begin
scl <= 1'b0;
cnt <= 1'b0;
i2c_data_r <= data_r;
end
default : ;
endcase
end
st_stop: begin //结束IIC操作
case(cnt)
7'd0: begin
sda_dir <= 1'b1; //结束IIC
sda_out <= 1'b0;
end
7'd1 : scl <= 1'b1;
7'd3 : sda_out <= 1'b1;
7'd15: st_done <= 1'b1;
7'd16: begin
cnt <= 1'b0;
i2c_done <= 1'b1; //向上层模块传递IIC结束信号
end
default : ;
endcase
end
endcase
end
end
endmodule
如图所示：
3.3 分析与综合
对设计进行分析，操作如图：
分析后的设计，Vivado自动生成顶层原理图，如图：
对设计进行综合，操作如图：
综合完成后，弹出窗口如下，直接关闭：
3.4 约束输入
创建约束文件，操作如图所示：
创建约束文件，输入文件名：
双击打开，输入约束代码：
set_property -dict {PACKAGE_PIN U18 IOSTANDARD LVCMOS33} [get_ports sys_clk]
set_property -dict {PACKAGE_PIN J15 IOSTANDARD LVCMOS33} [get_ports sys_rst_n]
如图所示：
3.5 设计实现
点击 Flow Navigator 窗口中的 Run Implementation，如图所示：
点击OK：
完成后，关闭即可：
3.6 功能仿真
创建TestBench，操作如图所示：
创建激励文件，输入文件名：
创建完成：
双击打开，输入TestBench(激励)代码：
`timescale 1ns/1ns //定义仿真时间单位1ns和仿真时间精度为1ns
module tb_iic_drive;
//parameter define
parameter T = 20; //时钟周期为20ns
parameter IIC_WR_CYCYLE = 10_000;
parameter SLAVE_ADDR = 7'b1010000 ; //EEPROM从机地址
parameter CLK_FREQ = 26'd50_000_000; //模块输入的时钟频率
parameter I2C_FREQ = 18'd250_000; //IIC_SCL的时钟频率
//reg define
reg sys_clk; //时钟信号
reg sys_rst_n; //复位信号
reg i2c_exec ;
reg bit_ctrl ;
reg i2c_rh_wl ;
reg [15:0] i2c_addr ;
reg [7:0] i2c_data_w;
reg [3:0] flow_cnt ;
reg [13:0] delay_cnt ;
//wire define
wire [7:0] i2c_data_r;
wire i2c_done ;
wire i2c_ack ;
wire scl ;
wire sda ;
wire dri_clk ;
//给输入信号初始值
initial begin
sys_clk = 1'b0;
sys_rst_n = 1'b0; //复位
#(T+1) sys_rst_n = 1'b1; //在第21ns的时候复位信号信号拉高
end
//50Mhz的时钟，周期则为1/50Mhz=20ns,所以每10ns，电平取反一次
always #(T/2) sys_clk = ~sys_clk;
always @(posedge dri_clk or negedge sys_rst_n) begin
if(!sys_rst_n) begin
i2c_exec <= 1'b0;
bit_ctrl <= 1'b0;
i2c_rh_wl <= 1'b0;
i2c_addr <= 1'b0;
i2c_data_w <= 1'b0;
flow_cnt <= 1'b0;
delay_cnt <= 1'b0;
end
else begin
case(flow_cnt)
'd0 : flow_cnt <= flow_cnt + 1'b1;
'd1 : begin
i2c_exec <= 1'b1; //拉高触发信号
bit_ctrl <= 1'b1; //地址位选择信号 1: 16位
i2c_rh_wl <= 1'b0; //写操作
i2c_addr <= 16'h0555; //写地址
i2c_data_w <= 8'hAA; //写数据
flow_cnt <= flow_cnt + 1'b1;
end
'd2 : begin
i2c_exec <= 1'b0;
flow_cnt <= flow_cnt + 1'b1;
end
'd3 : begin
if(i2c_done)
flow_cnt <= flow_cnt + 1'b1;
end
'd4 : begin
delay_cnt <= delay_cnt + 1'b1;
if(delay_cnt == IIC_WR_CYCYLE - 1'b1)
flow_cnt <= flow_cnt + 1'b1;
end
'd5 : begin
i2c_exec <= 1'b1;
bit_ctrl <= 1'b1;
i2c_rh_wl <= 1'b1; //读操作
i2c_addr <= 16'h0555;
i2c_data_w <= 8'hAA;
flow_cnt <= flow_cnt + 1'b1;
end
'd6 : begin
i2c_exec <= 1'b0;
flow_cnt <= flow_cnt + 1'b1;
end
'd7 : begin
if(i2c_done)
flow_cnt <= flow_cnt + 1'b1;
end
default:;
endcase
end
end
pullup(sda);
//例化
iic_drive #(
.SLAVE_ADDR (SLAVE_ADDR), //EEPROM从机地址
.CLK_FREQ (CLK_FREQ ), //模块输入的时钟频率
.I2C_FREQ (I2C_FREQ ) //IIC_SCL的时钟频率
) u_iic_drive(
.clk (sys_clk),
.rst_n (sys_rst_n),
.i2c_exec (i2c_exec ),
.bit_ctrl (bit_ctrl ),
.i2c_rh_wl (i2c_rh_wl ),
.i2c_addr (i2c_addr ),
.i2c_data_w (i2c_data_w),
.i2c_data_r (i2c_data_r),
.i2c_done (i2c_done ),
.i2c_ack (i2c_ack ),
.scl (scl ),
.sda (sda ),
.dri_clk (dri_clk )
);
endmodule
如图所示：
开始进行仿真，操作如下：
开始仿真：
仿真波形如图：
致谢领航者ZYNQ开发板，开启FPGA学习之路！
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