tdraudio: implement multiple channels

tridoracpu/tridoracpu.srcs/tdraudio.v

@@ -1,27 +1,23 @@
 `timescale 1ns / 1ps
 
-module tdraudio #(DATA_WIDTH=32) (
+// waveform generator module (only pulse wave for now)
+module wavegen #(DATA_WIDTH=32, CLOCK_DIV_WIDTH=22, AMP_WIDTH=16) (
         input wire clk,
         input wire reset,
-        input wire [3:0] reg_sel,
+        input wire [1:0] reg_sel,
         output wire [DATA_WIDTH-1:0] rd_data,
         input wire [DATA_WIDTH-1:0] wr_data,
         input wire rd_en,
         input wire wr_en,
 
-        output wire pdm_out,
+        output wire [AMP_WIDTH-1:0] amp_val,
-        output wire gain_sel,
+        output wire running
-        output wire shutdown_n
     );
 
-    localparam CLOCK_DIV_WIDTH = 22;
-    localparam AMP_WIDTH = 16;
-
     localparam TDRAU_REG_CTL = 0;  /* control register */
     localparam TDRAU_REG_CLK = 1;  /* clock divider register */
     localparam TDRAU_REG_AMP = 2;  /* amplitude (volume) register */
 
-    wire audio_out;
     reg channel_enable;
     reg [CLOCK_DIV_WIDTH-1:0] clock_div;
     reg [CLOCK_DIV_WIDTH-1:0] div_count;
@@ -29,12 +25,10 @@ module tdraudio #(DATA_WIDTH=32) (
     reg [AMP_WIDTH-1:0] amp_start;
     reg [AMP_WIDTH-1:0] amp_out;
 
-    reg [AMP_WIDTH:0] deltasigma_acc;
+    //assign rd_data = {{DATA_WIDTH-8-CLOCK_DIV_WIDTH{1'b0}}, div_count, {7{1'b0}}, channel_enable};
-
+    assign rd_data = {8'b0, amp_start, {7{1'b0}}, channel_enable};
-    assign pdm_out = audio_out;
+    assign amp_val = amp_out;
-    assign rd_data = {{DATA_WIDTH-8-CLOCK_DIV_WIDTH{1'b0}}, div_count, {7{1'b0}}, channel_enable};
+    assign running = channel_enable;
-    assign gain_sel = 1;  // gain select: 0 -> 12dB, 1 -> 6dB
-    assign shutdown_n = channel_enable;
 
     /* channel enable flag */
     always @(posedge clk)
@@ -101,6 +95,64 @@ module tdraudio #(DATA_WIDTH=32) (
             // because div_count will become zero
             amp_phase <= 1;
     end
+endmodule
+
+module tdraudio #(DATA_WIDTH=32) (
+        input wire clk,
+        input wire reset,
+        input wire [6:0] io_addr,
+        output wire [DATA_WIDTH-1:0] rd_data,
+        input wire [DATA_WIDTH-1:0] wr_data,
+        input wire rd_en,
+        input wire wr_en,
+
+        output wire pdm_out,
+        output wire gain_sel,
+        output wire shutdown_n
+    );
+
+    localparam CLOCK_DIV_WIDTH = 22;
+    localparam AMP_WIDTH = 16;
+
+    wire chan_sel = io_addr[6:2];
+    wire [1:0] reg_sel = io_addr[1:0];
+
+    wire [AMP_WIDTH-1:0] chan0_amp;
+    wire [DATA_WIDTH-1:0] chan0_rd_data;
+    wire chan0_running;
+    wire chan0_sel = chan_sel == 0;
+    wire chan0_rd_en = chan0_sel && rd_en;
+    wire chan0_wr_en = chan0_sel && wr_en;
+
+    wire [AMP_WIDTH-1:0] chan1_amp;
+    wire [DATA_WIDTH-1:0] chan1_rd_data;
+    wire chan1_running;
+    wire chan1_sel = chan_sel == 1;
+    wire chan1_rd_en = chan1_sel && rd_en;
+    wire chan1_wr_en = chan1_sel && wr_en;
+
+    wire running = chan0_running || chan1_running;
+
+    assign rd_data = chan0_sel ? chan0_rd_data :
+                        chan1_sel ? chan1_rd_data :
+                        {DATA_WIDTH{1'b1}};
+
+    wavegen chan0(clk, reset, reg_sel,
+        chan0_rd_data, wr_data,
+        chan0_rd_en, chan0_wr_en,
+        chan0_amp, chan0_running);
+
+    wavegen chan1(clk, reset, reg_sel,
+        chan1_rd_data, wr_data,
+        chan1_rd_en, chan1_wr_en,
+        chan1_amp, chan1_running);
+
+    reg [AMP_WIDTH:0] deltasigma_acc; // one extra bit
+    wire [AMP_WIDTH:0] amp_sum = chan0_amp + chan1_amp; // also one overflow bit here
+    wire [AMP_WIDTH-1:0] amp_sum_scaled = amp_sum[AMP_WIDTH:1]; // shifted right to scale down
+    assign gain_sel = 1;  // gain select: 0 -> 12dB, 1 -> 6dB
+
+    assign shutdown_n = running;
 
     /* delta-sigma DAC */
     always @(posedge clk)
@@ -108,10 +160,10 @@ module tdraudio #(DATA_WIDTH=32) (
         if(reset)
             deltasigma_acc <= 0;
         else
-        if (channel_enable)
+        if (running)
-            deltasigma_acc <= deltasigma_acc[AMP_WIDTH-1:0] + amp_out;
+            deltasigma_acc <= deltasigma_acc[AMP_WIDTH-1:0] + amp_sum_scaled;
     end
 
     /* 1-bit audio output */
-    assign audio_out = deltasigma_acc[AMP_WIDTH];
+    assign pdm_out = deltasigma_acc[AMP_WIDTH];
 endmodule

tridoracpu/tridoracpu.srcs/top.v

@@ -248,7 +248,7 @@ module top(
     assign tdraudio_wr_data = mem_write_data;
 
     tdraudio tdraudio0(`clock, ~rst,
-        mem_addr[3:0],
+        mem_addr[6:0],
         tdraudio_rd_data,
         tdraudio_wr_data,
         tdraudio_rd_en,