FPGA模块——IIC协议（FPGA做主机操作24C64）
- EEPROM（24C64）
- 向器件写数据时序
- 向器件读数据时序
- IIC协议
- FPGA主机代码
- IIC驱动
EEPROM（24C64）
掉电不丢失，采用固定的读写协议。数据的稳定性和可重复擦写性突出
电路设计，可以配置24C64的地址
从器件进行开漏输出：输出低电平，输出高阻态来让上拉电路拉高给主机
传输的器件地址格式
发送字（寄存器）地址：
有16位，24C64实际用到13位寄存器地址
向器件写数据时序
单次写的协议：
连续写的协议：
向器件读数据时序
从当前地址读：
从当任意地址读：
要先向器件进行虚写命令，再进行读命令。
从任意地址连续读：
不读了主机FPGA进行非应答
IIC协议
当SCL和SDA为高，SDA突然拉低的时候，是起始信号（下降沿）。
当SCL为高时，SDA突然拉高，是结束信号（上升沿）。高位在前
重点是：SCL在低电平期间SDA可以进行数据变化，而SCL在高电平期间，SDA的数据要保持稳定。
FPGA主机代码
为了可适配性，iic用的都是用指定地址单次写（任意地址单次写）。
1.写：器件地址+写命令（8位）以及字节地址（8/16位）
2.写数据（8位）
指定地址单次读（任意地址单次读）：
1.虚写：器件地址+写命令以及字节地址（8/16位）
2.发送器件地址+读命令（8位）
3.进行读数据（8位）
IIC驱动
使用三段式状态机：
//1.同步时序描述状态转移， 把下个状态给当前状态。
always @(posedge dri_clk or negedge rst_n)
//2.组合逻辑判断状态转移条件。（哪个信号变化了要转状态）
always @(*)
//3.时序电路描述状态输出，写每个状态里面要输出什么。
always @(posedge dri_clk or negedge rst_n)
module i2c_dri
#(
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
)
(
input clk ,
input rst_n ,
//i2c interface
input i2c_exec , //I2C触发执行信号
input bit_ctrl , //字地址位控制(16b/8b)
input i2c_rh_wl , //I2C读写控制信号
input [15:0] i2c_addr , //I2C器件内地址
input [ 7:0] i2c_data_w , //I2C要写的数据
output reg [ 7:0] i2c_data_r , //I2C读出的数据
output reg i2c_done , //I2C一次操作完成
output reg i2c_ack , //I2C应答标志 0:应答 1:未应答
output reg scl , //I2C的SCL时钟信号
inout sda , //I2C的SDA信号
//user interface
output reg dri_clk //驱动I2C操作的驱动时钟
);
//localparam define
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I2C操作
//reg define
reg sda_dir ; //I2C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 ; //I2C需写的数据的临时寄存
reg [ 9:0] clk_cnt ; //分频时钟计数
//wire define
wire sda_in ; //SDA输入信号
wire [8:0] clk_divide ; //模块驱动时钟的分频系数
//*****************************************************
//** main code
//*****************************************************
//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I2C的SCL的四倍频率的驱动时钟用于驱动i2c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] - 9'd1)) begin
clk_cnt <= 10'd0;
dri_clk <= ~dri_clk;
end
else
clk_cnt <= clk_cnt + 10'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 <= 7'b0;
st_done <= 1'b0;
data_r <= 8'b0;
i2c_data_r<= 8'b0;
wr_flag <= 1'b0;
addr_t <= 16'b0;
data_wr_t <= 8'b0;
end
else begin
st_done <= 1'b0 ;
cnt <= cnt +7'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I2C
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 <= 7'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 <= 7'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 <= 7'b0;
end
default : ;
endcase
end
st_data_wr: begin //写数据(8 bit)
case(cnt)
7'd0: begin
sda_dir <= 1'b1;
sda_out <= data_wr_t[7]; //I2C写8位数据
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 <= 7'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 <= 7'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 <= 7'b0;
i2c_data_r <= data_r;
end
default : ;
endcase
end
st_stop: begin //结束I2C操作
case(cnt)
7'd0: begin
sda_dir <= 1'b1; //结束I2C
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 <= 7'b0;
i2c_done <= 1'b1; //向上层模块传递I2C结束信号
end
default : ;
endcase
end
endcase
end
end
endmodule
