From d784f6d2515ae1a3027c08c555f16168ec13dc43 Mon Sep 17 00:00:00 2001
From: Aadi Desai <21363892+supleed2@users.noreply.github.com>
Date: Sun, 28 May 2023 16:07:23 +0100
Subject: [PATCH] Add sine wave generator using cordic

---
 .gitignore     |  1 -
 rtl/genSaw.sv  |  5 ++++-
 rtl/saw2sin.sv | 29 +++++++++++++++++++++++++++++
 testSaw.py     |  2 ++
 4 files changed, 35 insertions(+), 2 deletions(-)
 create mode 100644 rtl/saw2sin.sv

diff --git a/.gitignore b/.gitignore
index 79d362a..f712587 100644
--- a/.gitignore
+++ b/.gitignore
@@ -12,4 +12,3 @@
 /dump-*.vcd
 /*.dfu
 /kernel.bin
-/sintest/
diff --git a/rtl/genSaw.sv b/rtl/genSaw.sv
index f4e6e14..69948ee 100644
--- a/rtl/genSaw.sv
+++ b/rtl/genSaw.sv
@@ -45,7 +45,10 @@ logic [15:0] triangle;
 always_comb triangle = saw[15] ? {~saw[14:0], 1'b1} : {saw[14:0], 1'b0}; // Triangle wave calc
 
 logic [15:0] sine;
-always_comb sine = saw; // TODO: Insert sine calcuation here?
+saw2sin m_saw2sin // Instantiate saw2sin module
+( .i_saw(saw)
+, .o_sin(sine)
+);
 
 always_comb // Select output waveform
   case (i_wave[1:0])
diff --git a/rtl/saw2sin.sv b/rtl/saw2sin.sv
new file mode 100644
index 0000000..f3aee26
--- /dev/null
+++ b/rtl/saw2sin.sv
@@ -0,0 +1,29 @@
+`default_nettype none
+
+module saw2sin
+( 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 [15:0] qsin;
+cordic cordic
+( .i_qph (qsaw)
+, .o_sin (qsin)
+);
+
+always_comb o_sin = invert
+  ? ~{1'b1, qsin[15:1]} + 1 // Invert
+  : {1'b1, qsin[15:1]};     // Normal
+
+endmodule
diff --git a/testSaw.py b/testSaw.py
index 5599965..43ec89d 100644
--- a/testSaw.py
+++ b/testSaw.py
@@ -14,6 +14,8 @@ class TestSaw(Module, AutoCSR, ModuleDoc):
     Set the expected frequency sawtooth wave to be output via the headphone port.
     """
     def __init__(self, platform, pads):
+        platform.add_source("rtl/cordic.sv")
+        platform.add_source("rtl/saw2sin.sv")
         platform.add_source("rtl/genSaw.sv")
         platform.add_source("rtl/dacDriver.sv")