基于FPGA的MCP4725驱动程序

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我是靠谱客的博主笨笨蜗牛，这篇文章主要介绍基于FPGA的MCP4725驱动程序，现在分享给大家，希望可以做个参考。

基于FPGA的MCP4725驱动程序

芯片资料
MCP4725是低功耗、高精度、单通道的12位缓冲电压输出数模转换器（Digital-to-Analog Convertor，DAC)，具有非易失性存储器（EEPROM)。用户可以使用I2C接口命令将DAC输入和配置数据烧写到非易失性存储器（EEPROM)。非易失性存储器功能使得DAC器件在断电期间仍能保持DAC输入代码，且DAC输出在上电后立即可用。

                                                    图1.MCP4725功能框图
      MCP4725具有外部A0地址位选择引脚。此A0引脚可连接用户应用电路板的VDD或VSS。MCP4725具有2线型IIC兼容串行接口，可用于标准（100 kHz）、快速（400 kHz）或高速（3.4 MHz）模式。
图2.MCP4725封装类型
   Vout：模拟输出电压；
   Vss：参考地；
   VDD：电源电压；3.7~5.5V
   SDA：IIC串行数据；
   SCL：IIC串行时钟输入
   A0：地址位选择引脚；该引脚可连接到VSS或VDD ，或由数字逻辑电平有效驱动。该引脚的逻辑状态决定了I2 C地址位的A0位。
2. 输出电压计算
在这里插入图片描述
      例如当我们输入0x400，即十进制数1024，电源电压接入为5V，那么输出电压Vout=5*1024/4096=1.25V。
3. 工作原理
      当器件连接到I2C总线时，器件作为从器件工作。使用I2C接口命令，主器件可以读/写DAC输入寄存器或EEPROM。MCP4725器件地址包含4个固定位(1100 =器件代码)和3个地址位(A2、A1和A0)。A2和A1位是在出厂前硬连线的，而A0位由A0引脚的逻辑状态决定。A0引脚可连接到VDD或VSS，或由数字逻辑电平有效驱动。写命令用于将配置位和DAC输入代码装载到DAC寄存器，或写入器件的EEPROM。通过使用3个写命令类型位(C2、C1和C0)定义写命令类型。
在这里插入图片描述
      当C2=0,C1=0 时，为快速模式，此命令用于更改DAC寄存器，EEPROM不受影响；当C2=0,C1=1,C0=0 时，为写DAC寄存器模式，即将配置位和数据代码装载到DAC寄存器；当C2=0,C1=1,C0=1 时，为写DAC寄存器和更新EEPROM模式,将配置位和数据代码装载到DAC寄存器并且写入EEPROM中。本次主要使用写DAC寄存器模式和写DAC寄存器和更新EEPROM模式，如下图所示。
在这里插入图片描述
      第一个字节为器件寻址，A2和A1已经被厂家设置为0，A0由自己控制(默认为0，即接地)，因此第一个字节为0x60；第二个字节为写数据地址，PD0和PD1都为0时为正常模式，因此第二个字节为0x60；第三个字节和第四个字节的高4位组成12位数据输入，由我们自己定义输入。
4. IIC串行通信
      MCP4725器件使用2线IIC串行接口，该接口可在标准、快速或高速模式下工作。在总线上发送数据的器件定义为发送器，而接收数据的器件定义为接收器。总线必须由主器件控制，主器件产生串行时(SCL)信号、控制总线访问权并产生启动条件和停止条件。MCP4725器件作为从器件工作。主器件和从器件都可以作为发送器或接收器工作，但是由主器件决定激活哪种模式。通信由主器件（单片机）发起，它发送启动位，随后是从地址字节。发送的第一个字节始终为从地址字节，它包含器件代码、地址位和R/W位。MCP4725器件的器件代码为1100。当器件接收到读命令(R/W = 1)时，发送DAC输入寄存器和EEPROM的内容。下图给出了IIC通信时序要求。
在这里插入图片描述
      在本次设计中，SCL时钟输入频率选择为250KHz，FPGA工作时钟为50MHz，上电等待20ms后开始IIC数据写入。采用模块化设计，分为IIC驱动设计，MCP4725初始化设计，顶层模块。
5. 代码模块

5.1 IIC驱动模块

复制代码

module i2c_dri
    #(// slave address（器件地址）
      parameter   SLAVE_ADDR =  7'b1100000  ,
      parameter   CLK_FREQ   = 26'd50_000_000,   //  时钟频率(CLK_FREQ)
      parameter   I2C_FREQ   = 18'd250_000       // I2C的SCL时钟频率
     )(
          //global clock
          input                clk        ,      // 时钟
          input                rst_n      ,      // 复位信号

//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        [15:0]  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          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    [15:0]  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

//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) >> 3;   // 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'b1;
        clk_cnt <= 10'd0;
    end
    else if(clk_cnt == clk_divide - 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;
        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;
                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;               // 从机应答
                        sda_out <= 1'b1;
                    end
                    7'd37: scl     <= 1'b1;
                    7'd38: st_done <= 1'b1;
                    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;               // 从机应答
                        sda_out <= 1'b1;
                    end
                    7'd33: scl     <= 1'b1;
                    7'd34: st_done <= 1'b1;
                    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;               // 从机应答
                        sda_out <= 1'b1;
                    end
                    7'd33: scl     <= 1'b1;
                    7'd34: st_done <= 1'b1;
                    7'd35: begin
                        scl <= 1'b0;
                        cnt <= 1'b0;
                    end
                    default :  ;
                endcase
            end
            st_data_wr: begin                          // 写数据(12 bit)
                case(cnt)
                    7'd0: begin
                        sda_out <= data_wr_t[15];       // I2C写2次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[14];
                    7'd5 : scl <= 1'b1;
                    7'd7 : scl <= 1'b0;
                    7'd8 : sda_out <= data_wr_t[13];
                    7'd9 : scl <= 1'b1;
                    7'd11: scl <= 1'b0;
                    7'd12: sda_out <= data_wr_t[12];
                    7'd13: scl <= 1'b1;
                    7'd15: scl <= 1'b0;
                    7'd16: sda_out <= data_wr_t[11];
                    7'd17: scl <= 1'b1;
                    7'd19: scl <= 1'b0;
                    7'd20: sda_out <= data_wr_t[10];
                    7'd21: scl <= 1'b1;
                    7'd23: scl <= 1'b0;
                    7'd24: sda_out <= data_wr_t[9];
                    7'd25: scl <= 1'b1;
                    7'd27: scl <= 1'b0;
                    7'd28: sda_out <= data_wr_t[8];
                    7'd29: scl <= 1'b1;
                    7'd31: scl <= 1'b0;
                    7'd32: begin
                        sda_dir <= 1'b0;               // 从机应答
                        sda_out <= 1'b1;
                    end
                    7'd33: scl <= 1'b1;
              
                    7'd35: scl  <= 1'b0;
                    7'd36: sda_out <= data_wr_t[7];
					     7'd37: scl <= 1'b1;
					     
					     7'd39: scl  <= 1'b0;
					     7'd40: sda_out <= data_wr_t[6];
					     7'd41: scl <= 1'b1;
		              
						  7'd43: scl  <= 1'b0;
					     7'd44: sda_out <= data_wr_t[5];
					     7'd45: scl <= 1'b1;
						
				        7'd47: scl  <= 1'b0;
					     7'd48: sda_out <= data_wr_t[4];
					     7'd49: scl <= 1'b1;
						  
						  7'd51: scl  <= 1'b0;
					     7'd52: sda_out <= data_wr_t[3];
					     7'd53: scl <= 1'b1;
						  
						  7'd55: scl  <= 1'b0;
					     7'd56: sda_out <= data_wr_t[2];
					     7'd57: scl <= 1'b1;
						  
						  7'd59: scl  <= 1'b0;
					     7'd60: sda_out <= data_wr_t[1];
					     7'd61: scl <= 1'b1;
						  
						  7'd63: scl  <= 1'b0;
					     7'd64: sda_out <= data_wr_t[0];
					     7'd65: scl <= 1'b1;
						  
						  7'd67: scl <= 1'b0;
                    7'd68: begin
                        sda_dir <= 1'b0;               // 从机应答
                        sda_out <= 1'b1;
                    end
                    7'd69: scl <= 1'b1;
                    7'd70: st_done <= 1'b1;
                    7'd71: 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;               // 从机应答
                        sda_out <= 1'b1;
                    end
                    7'd37: scl     <= 1'b1;
                    7'd38: st_done <= 1'b1;
                    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;              // 非应答
                        sda_out <= 1'b1;
                    end
                    7'd33: scl     <= 1'b1;
                    7'd34: st_done <= 1'b1;
                    7'd35: begin
                        scl <= 1'b0;
                        cnt <= 1'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      <= 1'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

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module i2c_dri
    #(// slave address（器件地址）
      parameter   SLAVE_ADDR =  7'b1100000  ,
      parameter   CLK_FREQ   = 26'd50_000_000,   //  时钟频率(CLK_FREQ)
      parameter   I2C_FREQ   = 18'd250_000       // I2C的SCL时钟频率
     )(
          //global clock
          input                clk        ,      // 时钟
          input                rst_n      ,      // 复位信号

          //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        [15:0]  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          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    [15:0]  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



//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) >> 3;   // 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'b1;
        clk_cnt <= 10'd0;
    end
    else if(clk_cnt == clk_divide - 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;
        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;
                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;               // 从机应答
                        sda_out <= 1'b1;
                    end
                    7'd37: scl     <= 1'b1;
                    7'd38: st_done <= 1'b1;
                    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;               // 从机应答
                        sda_out <= 1'b1;
                    end
                    7'd33: scl     <= 1'b1;
                    7'd34: st_done <= 1'b1;
                    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;               // 从机应答
                        sda_out <= 1'b1;
                    end
                    7'd33: scl     <= 1'b1;
                    7'd34: st_done <= 1'b1;
                    7'd35: begin
                        scl <= 1'b0;
                        cnt <= 1'b0;
                    end
                    default :  ;
                endcase
            end
            st_data_wr: begin                          // 写数据(12 bit)
                case(cnt)
                    7'd0: begin
                        sda_out <= data_wr_t[15];       // I2C写2次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[14];
                    7'd5 : scl <= 1'b1;
                    7'd7 : scl <= 1'b0;
                    7'd8 : sda_out <= data_wr_t[13];
                    7'd9 : scl <= 1'b1;
                    7'd11: scl <= 1'b0;
                    7'd12: sda_out <= data_wr_t[12];
                    7'd13: scl <= 1'b1;
                    7'd15: scl <= 1'b0;
                    7'd16: sda_out <= data_wr_t[11];
                    7'd17: scl <= 1'b1;
                    7'd19: scl <= 1'b0;
                    7'd20: sda_out <= data_wr_t[10];
                    7'd21: scl <= 1'b1;
                    7'd23: scl <= 1'b0;
                    7'd24: sda_out <= data_wr_t[9];
                    7'd25: scl <= 1'b1;
                    7'd27: scl <= 1'b0;
                    7'd28: sda_out <= data_wr_t[8];
                    7'd29: scl <= 1'b1;
                    7'd31: scl <= 1'b0;
                    7'd32: begin
                        sda_dir <= 1'b0;               // 从机应答
                        sda_out <= 1'b1;
                    end
                    7'd33: scl <= 1'b1;
              
                    7'd35: scl  <= 1'b0;
                    7'd36: sda_out <= data_wr_t[7];
					     7'd37: scl <= 1'b1;
					     
					     7'd39: scl  <= 1'b0;
					     7'd40: sda_out <= data_wr_t[6];
					     7'd41: scl <= 1'b1;
		              
						  7'd43: scl  <= 1'b0;
					     7'd44: sda_out <= data_wr_t[5];
					     7'd45: scl <= 1'b1;
						
				        7'd47: scl  <= 1'b0;
					     7'd48: sda_out <= data_wr_t[4];
					     7'd49: scl <= 1'b1;
						  
						  7'd51: scl  <= 1'b0;
					     7'd52: sda_out <= data_wr_t[3];
					     7'd53: scl <= 1'b1;
						  
						  7'd55: scl  <= 1'b0;
					     7'd56: sda_out <= data_wr_t[2];
					     7'd57: scl <= 1'b1;
						  
						  7'd59: scl  <= 1'b0;
					     7'd60: sda_out <= data_wr_t[1];
					     7'd61: scl <= 1'b1;
						  
						  7'd63: scl  <= 1'b0;
					     7'd64: sda_out <= data_wr_t[0];
					     7'd65: scl <= 1'b1;
						  
						  7'd67: scl <= 1'b0;
                    7'd68: begin
                        sda_dir <= 1'b0;               // 从机应答
                        sda_out <= 1'b1;
                    end
                    7'd69: scl <= 1'b1;
                    7'd70: st_done <= 1'b1;
                    7'd71: 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;               // 从机应答
                        sda_out <= 1'b1;
                    end
                    7'd37: scl     <= 1'b1;
                    7'd38: st_done <= 1'b1;
                    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;              // 非应答
                        sda_out <= 1'b1;
                    end
                    7'd33: scl     <= 1'b1;
                    7'd34: st_done <= 1'b1;
                    7'd35: begin
                        scl <= 1'b0;
                        cnt <= 1'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      <= 1'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

5.2 MCP4725初始化模块

复制代码

module MCP4725_init( 
 
    input                clk      ,   //时钟信号
    input                rst_n    ,   //复位信号，低电平有效
    
    input                i2c_done ,   //I2C寄存器配置完成信号
    output  reg          i2c_exec ,   //I2C触发执行信号   
    output  reg  [23:0]  i2c_data    //I2C要配置的地址与数据(高16位地址,低8位数据)
);

//reg define
reg   [14:0]   start_init_cnt;        //等待延时计数器

//scl配置成250khz,输入的clk为1Mhz,周期为1us,20000*1us = 20ms
//上电到开始配置IIC至少等待20ms
always @(posedge clk or negedge rst_n) begin
    if(!rst_n)
        start_init_cnt <= 15'd0;
    else if(start_init_cnt < 15'd20000)
        start_init_cnt <= start_init_cnt + 1'b1;                    
end

//i2c触发执行信号   
always @(posedge clk or negedge rst_n) begin
    if(!rst_n)
        i2c_exec <= 1'b0;
    else if(start_init_cnt == 15'd19999)
        i2c_exec <= 1'b1;

else
        i2c_exec <= 1'b0;
end

//配置寄存器地址与数据
always @(posedge clk or negedge rst_n) begin
    if(!rst_n)
        i2c_data <= 16'd0;
	 else 
	     i2c_data <= {8'h60,8'h40,8'h00} ;//第一个字节为模式控制（60:同步更新到EEPROM;40:只更新DAC寄存器），后面两个字节为输入数据，取高12位
	 
	 end
endmodule

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module MCP4725_init( 
 
    input                clk      ,   //时钟信号
    input                rst_n    ,   //复位信号，低电平有效
    
    input                i2c_done ,   //I2C寄存器配置完成信号
    output  reg          i2c_exec ,   //I2C触发执行信号   
    output  reg  [23:0]  i2c_data    //I2C要配置的地址与数据(高16位地址,低8位数据)
);




//reg define
reg   [14:0]   start_init_cnt;        //等待延时计数器



//scl配置成250khz,输入的clk为1Mhz,周期为1us,20000*1us = 20ms
//上电到开始配置IIC至少等待20ms
always @(posedge clk or negedge rst_n) begin
    if(!rst_n)
        start_init_cnt <= 15'd0;
    else if(start_init_cnt < 15'd20000)
        start_init_cnt <= start_init_cnt + 1'b1;                    
end



//i2c触发执行信号   
always @(posedge clk or negedge rst_n) begin
    if(!rst_n)
        i2c_exec <= 1'b0;
    else if(start_init_cnt == 15'd19999)
        i2c_exec <= 1'b1;

    else
        i2c_exec <= 1'b0;
end 



//配置寄存器地址与数据
always @(posedge clk or negedge rst_n) begin
    if(!rst_n)
        i2c_data <= 16'd0;
	 else 
	     i2c_data <= {8'h60,8'h40,8'h00} ;//第一个字节为模式控制（60:同步更新到EEPROM;40:只更新DAC寄存器），后面两个字节为输入数据，取高12位
	 
	 end
endmodule

5.3 顶层模块

复制代码

module MCP4725_CTRL(

input clk,
  input rst_n,
  
  output scl,
  inout sda

);

wire                  i2c_exec        ;  //I2C触发执行信号
  wire   [23:0]         i2c_data        ;  //I2C要配置的地址与数据(高8位地址,低16位数据)          
  wire                  i2c_done        ;  //I2C寄存器配置完成信号
  wire                  i2c_dri_clk     ;  //I2C操作时钟
  
  parameter  SLAVE_ADDR = 7'h60         ;  //MCP4725的器件地址7'h60
  parameter  BIT_CTRL   = 1'b0          ;  //字节地址为8位  0:8位 1:16位
  parameter  CLK_FREQ   = 26'd50_000_000;  //时钟频率 50MHz
  parameter  I2C_FREQ   = 18'd250_000   ;  //I2C的SCL时钟频率,250KHz

i2c_dri 
   #(
    .SLAVE_ADDR         (SLAVE_ADDR),       //参数传递
    .CLK_FREQ           (CLK_FREQ  ),              
    .I2C_FREQ           (I2C_FREQ  )                
    )   
   u_i2c_dri(   
    .clk                (clk       ),
    .rst_n              (rst_n     ),   
        
    .i2c_exec           (i2c_exec  ),   
    .bit_ctrl           (BIT_CTRL  ),   
    .i2c_rh_wl          (1'b0),             //固定为0，只用到了IIC驱动的写操作   
    .i2c_addr           (i2c_data[23:16]),   
    .i2c_data_w         (i2c_data[15:0]),   
    .i2c_data_r         (),   
    .i2c_done           (i2c_done  ),   
    .scl                (scl   ),   
    .sda                (sda   ),   
        
    .dri_clk            (i2c_dri_clk)       //I2C操作时钟
); 
  
MCP4725_init u_MCP4725_init( 
 
   .clk     (i2c_dri_clk),   //时钟信号
   .rst_n   (rst_n),   //复位信号，低电平有效
   .i2c_done(i2c_done),   //I2C寄存器配置完成信号
   .i2c_exec(i2c_exec),   //I2C触发执行信号   
   .i2c_data(i2c_data)   //I2C要配置的地址与数据(高8位地址,低16位数据)
);
  
  
  
endmodule

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module MCP4725_CTRL(

  input clk,
  input rst_n,
  
  output scl,
  inout sda

);

  wire                  i2c_exec        ;  //I2C触发执行信号
  wire   [23:0]         i2c_data        ;  //I2C要配置的地址与数据(高8位地址,低16位数据)          
  wire                  i2c_done        ;  //I2C寄存器配置完成信号
  wire                  i2c_dri_clk     ;  //I2C操作时钟
  
  parameter  SLAVE_ADDR = 7'h60         ;  //MCP4725的器件地址7'h60
  parameter  BIT_CTRL   = 1'b0          ;  //字节地址为8位  0:8位 1:16位
  parameter  CLK_FREQ   = 26'd50_000_000;  //时钟频率 50MHz
  parameter  I2C_FREQ   = 18'd250_000   ;  //I2C的SCL时钟频率,250KHz

  
 i2c_dri 
   #(
    .SLAVE_ADDR         (SLAVE_ADDR),       //参数传递
    .CLK_FREQ           (CLK_FREQ  ),              
    .I2C_FREQ           (I2C_FREQ  )                
    )   
   u_i2c_dri(   
    .clk                (clk       ),
    .rst_n              (rst_n     ),   
        
    .i2c_exec           (i2c_exec  ),   
    .bit_ctrl           (BIT_CTRL  ),   
    .i2c_rh_wl          (1'b0),             //固定为0，只用到了IIC驱动的写操作   
    .i2c_addr           (i2c_data[23:16]),   
    .i2c_data_w         (i2c_data[15:0]),   
    .i2c_data_r         (),   
    .i2c_done           (i2c_done  ),   
    .scl                (scl   ),   
    .sda                (sda   ),   
        
    .dri_clk            (i2c_dri_clk)       //I2C操作时钟
); 
  
MCP4725_init u_MCP4725_init( 
 
   .clk     (i2c_dri_clk),   //时钟信号
   .rst_n   (rst_n),   //复位信号，低电平有效
   .i2c_done(i2c_done),   //I2C寄存器配置完成信号
   .i2c_exec(i2c_exec),   //I2C触发执行信号   
   .i2c_data(i2c_data)   //I2C要配置的地址与数据(高8位地址,低16位数据)
);
  
  
  
endmodule

PS：IIC驱动程序是我在以前写的IIC单字节读写程序的基础上修改而来，从而实现两个字节的写入(这里可以再增加实现多个字节的写入，但要注意cnt的位宽)。MCP4725初始化程序中最后的 i2c_data <= {8’h60,8’h40,8’h00} ; 这一行大家可以根据自己的实际需求做更改，详细更改的内容自行参考芯片的数据手册。

6.验证
将工程编译好后的sof文件下载到EP4CE6F17C8器件中，连接好MCP4725各个引脚，电源接5V，输入的数据为1024，为4096的四分之一，因此输出电压应该为1.25V，利用万用表测量数据为1.25V，将模块断电再重新上电，再次测量也为1.25V，证明数据成功写入EEPROM中，验证成功。