Fix audio DAC programmingabc80-de1-13

Quite a few of the sound DAC register settings were just plain wrong.
Fix them.

1 files changed, 6 insertions, 2 deletions

diff --git a/sound.v b/sound.v
index 887ff08..056d082 100644
--- a/sound.v
+++ b/sound.v
@@ -320,11 +320,15 @@ module sound_i2s(
      if (stb_16us)
        sample <= magnitude;
 
+   // We load serial_out after clock 1, which means each frame has two
+   // zero padding bits at the front.  Bit 0 is required by I2S standard
+   // format, and bit 1 means our unsigned output is always in the positive
+   // half of the signed number space.
    always @(posedge i2s_clk)
-     if (ctr[6:0] == 7'h00)
+     if (ctr[6:0] == 7'h01)
        serial_out <= sample;
      else
-       serial_out <= { serial_out[12:0], 1'b0 };
+       serial_out <= { serial_out[13:0], 1'b0 };
 
    sound_generator sound_generator (
 				    .clk (i2s_clk),