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FPGA实现I2C通信方案

news 2025/8/17 7:07:07

总体系统架构图

I2C控制器模块划分

关键时序图

完整写操作时序（写24C02 EEPROM）

状态机定义

时钟生成（100kHz）

测试方案

测试用例

总体系统架构图

I2C控制器模块划分

时钟分频模块：生成I2C时钟
主状态机：控制通信流程
移位寄存器：数据串并转换
ACK检测：响应检测逻辑
仲裁逻辑：多主竞争处理
三态控制：双向IO管理

关键时序图

SCL _______/‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾\_______/‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾\_______
SDA _____/‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾\___

 起始SDA↓ while SCL=H     结束 ↑ SDA↑ while SCL=H

完整写操作时序（写24C02 EEPROM）

Start 地址+W ACK 数据 ACK Stop
SCL ___/‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾\___
| | A6 A5 A4 A3 A2 A1 A0 W | | D7 D6 ... D0 | | |
SDA ___/‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾\_
| S | 1 0 1 0 0 0 0 0 | ACK | 0 1 ... 1 | ACK | P |
↑ 从机地址(0x50) + 写(0) ↓ 数据(0x5F) ↓

3. 读操作时序

Start 地址+R ACK 数据 NACK Stop
SCL ___/‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾\___
| | A6 A5 A4 A3 A2 A1 A0 R | | D7 D6 ... D0 | | |
SDA ___/‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾\_
| S | 1 0 1 0 0 0 0 1 | ACK | 1 0 ... 1 | NACK| P |
↑ 从机地址(0x50) + 读(1) ↓ 数据(0xA5) ↑(主机释放)

Verilog实现核心代码

状态机定义

localparam [3:0]IDLE      = 4'd0,START     = 4'd1,ADDR      = 4'd2,ACK_ADDR  = 4'd3,WR_DATA   = 4'd4,ACK_WR    = 4'd5,RD_DATA   = 4'd6,ACK_RD    = 4'd7,STOP      = 4'd8,RESTART   = 4'd9;

三态控制逻辑

// SDA双向控制
assign sda_out = (sda_oe) ? shift_reg[7] : 1'bz;
assign sda = sda_out;// SCL时钟控制
assign scl_out = (scl_oe) ? scl_clk : 1'bz;
assign scl = scl_out;// 输入采样
always @(posedge sys_clk) beginsda_in <= sda;scl_in <= scl;
end

状态机片段（写操作）

case(state)IDLE:if (start) beginscl_oe <= 1;sda_oe <= 1;state <= START;endSTART:if (scl_high) beginsda_oe <= 0;  // 产生下降沿shift_reg <= {slv_addr, 1'b0}; // 地址+写bit_cnt <= 7;state <= ADDR;endADDR:if (scl_fall) beginif (bit_cnt > 0) beginshift_reg <= {shift_reg[6:0], 1'b0};bit_cnt <= bit_cnt - 1;end else beginsda_oe <= 0; // 释放SDAstate <= ACK_ADDR;endendACK_ADDR:if (scl_rise) beginif (!sda_in) begin // 检测ACKshift_reg <= tx_data;bit_cnt <= 7;state <= WR_DATA;end else beginstate <= STOP; // NACK处理endend...
endcase

时钟生成（100kHz）

// 系统时钟50MHz -> I2C 100kHz
parameter DIV_CNT = 250; // 50e6 / (100e3 * 2) = 250always @(posedge sys_clk or negedge rst_n) beginif (!rst_n) beginclk_cnt <= 0;scl_clk <= 1;end else beginif (clk_cnt == DIV_CNT-1) beginclk_cnt <= 0;scl_clk <= ~scl_clk; // 翻转SCLend else beginclk_cnt <= clk_cnt + 1;endend
end// 时钟边沿检测
assign scl_rise = (scl_in_prev == 0) && (scl_in == 1);
assign scl_fall = (scl_in_prev == 1) && (scl_in == 0);

测试方案

逻辑分析仪捕获波形

        +--------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
SCL     | START | BIT7| BIT6| BIT5| BIT4| BIT3| BIT2| BIT1| BIT0| ACK | ... |+--------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
SDA     |   ↓   | A6  | A5  | A4  | A3  | A2  | A1  | A0  | W/R |  ↓  | ... |+--------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+