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Clickless CW Sidetone (3)

wave45

Using a PCM5102A dac with typical performance of SNR 112dB, Dynamic Range 112dB, THD+N@-1dBFS -93dB.

wave49

The envelope is shaped as a raised cosine over 512 samples at Fs=48kHz.

wave46

wave47

reg signed [15:0] sine_table;
always @(sound_index) begin
    case (sound_index) 
        7'b0000000: begin sine_table <= 16'b0000000000000000; end //      0:         0 
//
        7'b1001111: begin sine_table <= 16'b1111010111110110; end //     79:     -2570 

reg signed [15:0] shape;
always @(envelope) begin
    case (envelope) 
        9'b 000000000 : begin shape <= 16'b0000000000000000; end //   0:     0 
//
        9'b 111111111 : begin shape <= 16'b0111111111111110; end // 511: 32766 

reg signed [31:0] mult; // sine_table: signed 16bit, shape: signed 16-bit
always @(sound_index) begin
   mult <= shape * sine_table;
end

always @ (posedge clk_myown or negedge res_n)
 begin
  if ( res_n == 1'b0 )
   daword <= 6'b00_0000;
  else begin
   daword <= daword + 6'b00_0001;
   if ( daword[4:0] == 5'b0_0000 ) // for each 32-bit, or for each L and R
	dadata <= {mult[30:0], 1'b0};
   else
	dadata <= {dadata[30:0], 1'b0};
  end
 end

wave48

The sidetone signal is analogue captured at Fs=48kHz.