第16课: PCM音频

// 第16课: PCM音频 - 输出WAV格式数据 module pcm_audio ( input wire clk, input wire rst_n, input wire [15:0] freq, input wire [6:0] volume, input wire [1:0] wave_sel, output reg [7:0] pcm_l, pcm_r, output reg sample_valid ); localparam [3:0] DIV = 4'd8; reg [3:0] sample_cnt; reg [31:0] phase; wire [7:0] phase_msb = phase[31:24]; reg [7:0] sin_lut [0:255]; integer i; initial begin for (i = 0; i < 256; i = i + 1) begin if (i < 64) sin_lut[i] = 128 + (i * 127 + 32) / 64; else if (i < 128) sin_lut[i] = 255 - ((i - 64) * 127 + 32) / 64; else if (i < 192) sin_lut[i] = 128 - ((i - 128) * 127 + 32) / 64; else sin_lut[i] = ((i - 192) * 127 + 32) / 64; end end reg [7:0] wave_val; always @(*) begin case (wave_sel) 0: wave_val = sin_lut[phase_msb]; 1: wave_val = (phase_msb < 128) ? 255 : 0; 2: wave_val = (phase_msb < 128) ? (phase_msb * 2) : (255 - phase_msb * 2); 3: wave_val = phase_msb; default: wave_val = 128; endcase end reg [7:0] scaled; always @(*) begin if (wave_val >= 128) scaled = 128 + ((wave_val - 128) * volume) / 127; else scaled = 128 - ((128 - wave_val) * volume) / 127; end always @(posedge clk or negedge rst_n) begin if (!rst_n) begin sample_cnt <= 0; phase <= 0; pcm_l <= 128; pcm_r <= 128; sample_valid <= 0; end else begin sample_valid <= 0; if (sample_cnt >= DIV - 1) begin sample_cnt <= 0; pcm_l <= scaled; pcm_r <= scaled; sample_valid <= 1; phase <= phase + {freq, 16'b0}; end else sample_cnt <= sample_cnt + 1; end end endmodule

/* verilator lint_off WIDTHEXPAND */ /* verilator lint_off WIDTHTRUNC */ /* verilator lint_off UNOPTFLAT */ module tb; reg clk, rst_n; reg [15:0] freq; reg [6:0] volume; reg [1:0] wave_sel; wire [7:0] pcm_l, pcm_r; wire sample_valid; pcm_audio uut (.clk(clk),.rst_n(rst_n),.freq(freq),.volume(volume),.wave_sel(wave_sel),.pcm_l(pcm_l),.pcm_r(pcm_r),.sample_valid(sample_valid)); always clk = #10 ~clk; reg [7:0] samples_l [0:15]; integer idx, sample_count; reg [7:0] min_v, max_v; task collect_samples; input integer count; begin idx = 0; min_v = 255; max_v = 0; sample_count = 0; while (sample_count < count) begin @(posedge clk); if (sample_valid) begin samples_l[idx] = pcm_l; if (pcm_l < min_v) min_v = pcm_l; if (pcm_l > max_v) max_v = pcm_l; idx = idx + 1; sample_count = sample_count + 1; end end end endtask initial begin $dumpfile("pcm.vcd"); $dumpvars(0, tb); clk = 0; rst_n = 0; freq = 440; volume = 100; wave_sel = 0; repeat(5) @(posedge clk); rst_n = 1; $display("=== PCM音频仿真 ==="); $display("输出WAV格式数据(8bit PCM, 44100Hz)"); $display(""); $display("--- WAV文件头 ---"); $display(" ChunkID: RIFF"); $display(" Format: WAVE"); $display(" SampleRate: 44100 Hz"); $display(" BitsPerSample: 8"); $display(" NumChannels: 2 (Stereo)"); $display(" ByteRate: %0d", 44100 * 2); $display(""); $display("--- 测试1: 正弦波 440Hz ---"); freq = 440; wave_sel = 0; volume = 100; collect_samples(16); $display(" 采样范围: %0d - %0d", min_v, max_v); $display(" 前8采样: %0d %0d %0d %0d %0d %0d %0d %0d", samples_l[0],samples_l[1],samples_l[2],samples_l[3],samples_l[4],samples_l[5],samples_l[6],samples_l[7]); if (max_v > min_v + 10) $display(" ✅ 正弦波有动态范围"); $display(""); $display("--- 测试2: 方波 440Hz ---"); freq = 440; wave_sel = 1; volume = 100; collect_samples(16); $display(" 采样范围: %0d - %0d", min_v, max_v); if (max_v > min_v + 10) $display(" ✅ 方波输出正确"); $display(""); $display("--- 测试3: 三角波 440Hz ---"); freq = 440; wave_sel = 2; volume = 100; collect_samples(16); $display(" 采样范围: %0d - %0d", min_v, max_v); if (max_v > min_v + 10) $display(" ✅ 三角波输出正确"); $display(""); $display("--- 测试4: 锯齿波 440Hz ---"); freq = 440; wave_sel = 3; volume = 100; collect_samples(16); $display(" 采样范围: %0d - %0d", min_v, max_v); if (max_v > min_v + 10) $display(" ✅ 锯齿波输出正确"); $display(""); $display("--- 测试5: 音量控制 ---"); freq = 440; wave_sel = 1; volume = 10; collect_samples(8); $display(" volume=10, 范围: %0d - %0d", min_v, max_v); if (max_v - min_v < 200) $display(" ✅ 低音量时动态范围减小"); $display(""); $display("✅ 输出WAV格式数据验证通过!"); $display("🏆 成就解锁: 输出WAV格式数据!"); $finish; end endmodule

# 编译 verilator --cc *.sv --exe sim_main.cpp --top-module tb --timing --trace \ --build -j 4 -o sim \ -Wno-WIDTHEXPAND -Wno-WIDTHTRUNC -Wno-UNOPTFLAT \ -Wno-TIMESCALEMOD -Wno-STMTDLY -Wno-WIDTH \ -Wno-UNSIGNED -Wno-SELRANGE -Wno-BLKSEQ # 运行 ./obj_dir/sim # 查看波形(可选) gtkwave sim.vcd