From e132d52adf52b91cc44741c9d13c178219d7a5f5 Mon Sep 17 00:00:00 2001
From: Clyne Sullivan <clyne@bitgloo.com>
Date: Sun, 24 Jan 2021 13:16:20 -0500
Subject: error recv. draft; add trig/math funcs

---
 source/cordic.cpp | 94 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 94 insertions(+)
 create mode 100644 source/cordic.cpp

(limited to 'source/cordic.cpp')

diff --git a/source/cordic.cpp b/source/cordic.cpp
new file mode 100644
index 0000000..2a44015
--- /dev/null
+++ b/source/cordic.cpp
@@ -0,0 +1,94 @@
+#include "cordic.hpp"
+#include "hal.h"
+
+namespace math {
+
+void init()
+{
+    RCC->AHB2ENR |= RCC_AHB2ENR_CORDICEN;
+}
+
+static void prepare() {
+    while (CORDIC->CSR & CORDIC_CSR_RRDY)
+        asm("mov r0, %0" :: "r" (CORDIC->RDATA));
+}
+static uint32_t dtoq(double in) {
+    double res = in * 0x7FFFFFFF;
+    int32_t resi = res;
+    return resi;
+}
+static double qtod(uint32_t in) {
+    int32_t ini = in;
+    double res = ini;
+    return res / 0x7FFFFFFF;
+}
+
+__attribute__((naked))
+double mod(double n, double) {
+    asm("vdiv.f64   d2, d0, d1;"
+        "vrintz.f64 d2;"
+        "vmul.f64   d1, d1, d2;"
+        "vsub.f64   d0, d0, d1;"
+        "bx lr");
+    return n;
+}
+
+double cos(double x) {
+    x = (mod(x, 2 * math::PI) - math::PI) / math::PI;
+    prepare();
+    CORDIC->CSR = CORDIC_CSR_NARGS | CORDIC_CSR_NRES |
+                  (6 << CORDIC_CSR_PRECISION_Pos) |
+                  (0 << CORDIC_CSR_FUNC_Pos);
+
+    auto in = dtoq(x);
+    CORDIC->WDATA = in;
+    CORDIC->WDATA = in & 0x7FFFFFFF;
+    while (!(CORDIC->CSR & CORDIC_CSR_RRDY));
+
+    double cosx = qtod(CORDIC->RDATA) / x;
+    in = CORDIC->RDATA;
+    return cosx;
+}
+
+double sin(double x) {
+    x = (mod(x, 2 * math::PI) - math::PI) / math::PI;
+    prepare();
+    CORDIC->CSR = CORDIC_CSR_NARGS | CORDIC_CSR_NRES |
+                  (6 << CORDIC_CSR_PRECISION_Pos) |
+                  (1 << CORDIC_CSR_FUNC_Pos);
+
+    auto in = dtoq(x);
+    CORDIC->WDATA = in;
+    CORDIC->WDATA = in & 0x7FFFFFFF;
+    while (!(CORDIC->CSR & CORDIC_CSR_RRDY));
+
+    double sinx = qtod(CORDIC->RDATA) / x;
+    in = CORDIC->RDATA;
+    return sinx;
+}
+
+double tan(double x) {
+    x = (mod(x, 2 * math::PI) - math::PI) / math::PI;
+    prepare();
+    CORDIC->CSR = CORDIC_CSR_NARGS | CORDIC_CSR_NRES |
+                  (6 << CORDIC_CSR_PRECISION_Pos) |
+                  (1 << CORDIC_CSR_FUNC_Pos);
+
+    auto in = dtoq(x);
+    CORDIC->WDATA = in;
+    CORDIC->WDATA = in & 0x7FFFFFFF;
+    while (!(CORDIC->CSR & CORDIC_CSR_RRDY));
+
+    double sinx = qtod(CORDIC->RDATA) / x;
+    double tanx = sinx * x / qtod(CORDIC->RDATA);
+    return tanx;
+}
+
+__attribute__((naked))
+double sqrt(double x) {
+    asm("vsqrt.f64 d0, d0; bx lr");
+    return x;
+}
+
+}
+
-- 
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