EIE4-FYP/rtl/genSaw.sv

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`default_nettype none
module genSaw
( input var i_clk48
, input var i_rst48_n
, input var i_pause
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, input var [23:0] i_targetf
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, input var [ 7:0] i_wave
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, output var [15:0] o_sample
, output var o_pulse
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);
logic [8:0] clk_div;
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always_ff @(posedge i_clk48) // Count half 48kHz cycle
if (!i_rst48_n) clk_div <= 0;
else if (clk_div == 9'd499) clk_div <= 0;
else clk_div <= clk_div + 1;
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logic clk_48k;
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always_ff @(posedge i_clk48) // Generate 48kHz clock
if (!i_rst48_n) clk_48k <= 0;
else if (clk_div == 9'd0) clk_48k <= ~clk_48k;
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logic clk_48k_past;
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always_ff @(posedge i_clk48) // Track rising / falling edge of 48kHz clock
clk_48k_past <= clk_48k;
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always_comb o_pulse = clk_48k && !clk_48k_past; // Detect rising edge of 48kHz clock
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logic [23:0] int_saw_step;
always_comb int_saw_step = (24'd699 * i_targetf); // Sawtooth step calc from input target freq
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logic [15:0] saw_step;
always_comb saw_step = {1'b0, int_saw_step[23:9]}; // Shift step right correctly (2^9)
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logic [15:0] saw;
always_ff @(posedge clk_48k) // Generate new saw sample on rising edge of 48kHz clock
if (!i_rst48_n) saw <= '0;
else if (!i_pause) saw <= saw + saw_step; // Add saw_step if not paused (48kHz)
logic [15:0] square;
always_comb square = {~saw[15], {15{saw[15]}}}; // Square wave is MSB of saw
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logic [15:0] triangle;
always_comb triangle = saw[15] ? {~saw[14:0], 1'b1} : {saw[14:0], 1'b0}; // Triangle wave calc
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logic [15:0] sine;
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saw2sin m_saw2sin // Instantiate saw2sin module
( .i_saw(saw)
, .o_sin(sine)
);
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always_comb // Select output waveform
case (i_wave[1:0])
2'd0: o_sample = saw;
2'd1: o_sample = square;
2'd2: o_sample = triangle;
2'd3: o_sample = sine;
endcase
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endmodule