From e00149bb621d9e9534af5c263ba4f881dfe27f0a Mon Sep 17 00:00:00 2001
From: Aadi Desai <21363892+supleed2@users.noreply.github.com>
Date: Sun, 28 May 2023 16:03:39 +0100
Subject: [PATCH] Add saw2sin_poly.sv

Polynomial approximation to sine
Input 0-65535 represents 0-90 degrees
Output 0-65535 represents 0-1
---
 saw2sin_poly.sv | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)
 create mode 100644 saw2sin_poly.sv

diff --git a/saw2sin_poly.sv b/saw2sin_poly.sv
new file mode 100644
index 0000000..3180e5d
--- /dev/null
+++ b/saw2sin_poly.sv
@@ -0,0 +1,30 @@
+`default_nettype none
+
+module saw2sin_poly
+( input  var [15:0] i_saw
+, output var [15:0] o_sin
+);
+
+logic invert;
+always_comb invert = i_saw[15];
+
+logic reverse;
+always_comb reverse = i_saw[14];
+
+logic [15:0] qsaw;
+always_comb qsaw = reverse
+  ? {~i_saw[13:0], 2'b01} // Reverse
+  : {i_saw[13:0], 2'b00}; // Normal
+
+logic [63:0] x_in, x_17;
+always_comb x_in = {48'd0, qsaw};
+always_comb x_17 = 64'd131072 - x_in;
+
+logic [63:0] qsin;
+always_comb qsin = (64'd262144 * x_in * x_17) / (64'd21474836480 - (x_in * x_17));
+
+always_comb o_sin = invert
+  ? ~{1'b1, qsin[15:1]} + 1 // Invert
+  : {1'b1, qsin[15:1]};     // Normal
+
+endmodule