Added PWM modulator module and a testbench

Author: pConst

pwm_gen.sv

@@ -0,0 +1,89 @@
+//------------------------------------------------------------------------------
+// pwm_gen.sv
+// Konstantin Pavlov, pavlovconst@gmail.com
+//------------------------------------------------------------------------------
+
+// INFO ------------------------------------------------------------------------
+// PWM generator module
+//
+// - expecting 8-bit control signal input
+// - system clock is 100 MHz by default
+// - PWM clock is 1.5KHz by default
+
+
+/* --- INSTANTIATION TEMPLATE BEGIN ---
+
+pwm_gen #(
+  .CLK_HZ( 100_000_000 ),            // 100 MHz
+  .PWM_PERIOD_DIV( 16 )              // 100MHz/2^16= ~1.526 KHz
+
+  .MOD_WIDTH( 8 )                    // from 0 to 255
+) pwm1 (
+  .clk( clk ),
+  .nrst( nrst ),
+
+  .control(  ),
+  .pwm_out(  ),
+
+  .start_strobe(  ),
+  .busy(  )
+);
+
+--- INSTANTIATION TEMPLATE END ---*/
+
+module pwm_gen #( parameter
+  CLK_HZ = 100_000_000,
+  PWM_PERIOD_DIV = 16,                // must be > MOD_WIDTH
+  PWM_PERIOD_HZ = CLK_HZ / (2**PWM_PERIOD_DIV),
+
+  MOD_WIDTH = 8                       // modulation bitness
+)(
+  input clk,                          // system clock
+  input nrst,                         // negative reset
+
+  input [MOD_WIDTH-1:0] mod_setpoint, // modulation setpoint
+  output pwm_out,                     // active HIGH output
+
+  // status outputs
+  output start_strobe,                // period start strobe
+  output busy                         // busy output
+);
+
+
+// period generator
+logic [31:0] div_clk;
+clk_divider #(
+  .WIDTH( 32 )
+) cd1 (
+  .clk( clk ),
+  .nrst( nrst ),
+  .ena( 1'b1 ),
+  .out( div_clk[31:0] )
+);
+
+
+// optional setpoint inversion
+logic [MOD_WIDTH-1:0] mod_setpoint_inv;
+assign mod_setpoint_inv[MOD_WIDTH-1:0] = {MOD_WIDTH{1'b1}} - mod_setpoint[MOD_WIDTH-1:0];
+
+
+// pulse generator
+pulse_gen #(
+  .CNTR_WIDTH( MOD_WIDTH+1 )
+) pg1 (
+  .clk( div_clk[(PWM_PERIOD_DIV-1)-MOD_WIDTH] ),
+  .nrst( nrst ),
+
+  .start( 1'b1 ),
+  .cntr_max( {1'b0, {MOD_WIDTH{1'b1}} } ),
+  .cntr_low( {1'b0, mod_setpoint_inv[MOD_WIDTH-1:0] } ),
+
+  .pulse_out( pwm_out ),
+
+  .start_strobe( start_strobe ),
+  .busy( busy )
+);
+
+
+endmodule
+

pwm_gen_tb.sv

@@ -0,0 +1,136 @@
+//------------------------------------------------------------------------------
+// pwm_gen_tb.sv
+// Konstantin Pavlov, pavlovconst@gmail.com
+//------------------------------------------------------------------------------
+
+// INFO ------------------------------------------------------------------------
+// testbench for pwm_gen.sv module
+
+
+`timescale 1ns / 1ps
+
+module pwm_gen_tb();
+
+logic clk200;
+initial begin
+  #0 clk200 = 1'b0;
+  forever
+    #2.5 clk200 = ~clk200;
+end
+
+// external device "asynchronous" clock
+logic clk33;
+initial begin
+  #0 clk33 = 1'b0;
+  forever
+    #15.151 clk33 = ~clk33;
+end
+
+logic rst;
+initial begin
+  #0 rst = 1'b0;
+  #10.2 rst = 1'b1;
+  #5 rst = 1'b0;
+  //#10000;
+  forever begin
+    #9985 rst = ~rst;
+    #5 rst = ~rst;
+  end
+end
+
+logic nrst;
+assign nrst = ~rst;
+
+logic rst_once;
+initial begin
+  #0 rst_once = 1'b0;
+  #10.2 rst_once = 1'b1;
+  #5 rst_once = 1'b0;
+end
+
+logic nrst_once;
+assign nrst_once = ~rst_once;
+
+logic [31:0] DerivedClocks;
+clk_divider #(
+  .WIDTH( 32 )
+) cd1 (
+  .clk( clk200 ),
+  .nrst( nrst_once ),
+  .ena( 1'b1 ),
+  .out( DerivedClocks[31:0] )
+);
+
+logic [31:0] E_DerivedClocks;
+edge_detect ed1[31:0] (
+  .clk( {32{clk200}} ),
+  .nrst( {32{nrst_once}} ),
+  .in( DerivedClocks[31:0] ),
+  .rising( E_DerivedClocks[31:0] ),
+  .falling(  ),
+  .both(  )
+);
+
+logic [31:0] RandomNumber1;
+c_rand rng1 (
+  .clk( clk200 ),
+  .rst( 1'b0 ),
+  .reseed( rst_once ),
+  .seed_val( DerivedClocks[31:0] ^ (DerivedClocks[31:0] << 1) ),
+  .out( RandomNumber1[15:0] )
+);
+
+c_rand rng2 (
+  .clk( clk200 ),
+  .rst( 1'b0 ),
+  .reseed( rst_once ),
+  .seed_val( DerivedClocks[31:0] ^ (DerivedClocks[31:0] << 2) ),
+  .out( RandomNumber1[31:16] )
+);
+
+logic start;
+initial begin
+  #0 start = 1'b0;
+  #100 start = 1'b1;
+  #20 start = 1'b0;
+end
+
+// Modules under test ==========================================================
+
+localparam MOD_WIDTH = 5;
+
+logic [MOD_WIDTH-1:0] sp = '0;
+logic [31:0][MOD_WIDTH-1:0] sin_table =
+{ 5'd16, 5'd19, 5'd22, 5'd25, 5'd27, 5'd29, 5'd31, 5'd31,
+  5'd31, 5'd31, 5'd30, 5'd28, 5'd26, 5'd23, 5'd20, 5'd17,
+  5'd14, 5'd11, 5'd8,  5'd5,  5'd3,  5'd1,  5'd0,  5'd0,
+  5'd0,  5'd0,  5'd2,  5'd4,  5'd6,  5'd9,  5'd12, 5'd15};
+
+logic strobe;
+always_ff @(posedge clk200) begin
+  if( ~nrst_once ) begin
+    sp[MOD_WIDTH-1:0] <= '0;
+  end else begin
+    if( strobe ) begin
+      sp[MOD_WIDTH-1:0] <= sp[MOD_WIDTH-1:0] + 1'b1;
+    end
+  end
+end
+
+pwm_gen #(
+  .CLK_HZ( 200_000_000 ),
+  .PWM_PERIOD_DIV( MOD_WIDTH+1 ),     // MOD_WIDTH+1 is a minimum
+  .MOD_WIDTH( MOD_WIDTH )
+) pwm1 (
+  .clk( clk200 ),
+  .nrst( nrst_once ),
+
+  .mod_setpoint( sin_table[sp[MOD_WIDTH-1:0]][MOD_WIDTH-1:0] ),
+  .pwm_out(  ),
+
+  .start_strobe( strobe ),
+  .busy(  )
+);
+
+
+endmodule