initial WIP

lots of code copied over, things filled in to hopefully get the LED matrix lighting up. untested.

firmware/app/misc/i8atan2.c

@@ -0,0 +1,50 @@
+/*
+ * i8atan2.c
+ * begin 20190611 true
+ *
+ * copied and fixed up from teh internets
+ */
+
+
+#include <stdint.h>
+
+
+static int8_t iat2(int8_t y, int8_t x)
+{
+	return ((y * 32 + (x / 2)) / x) * 2;
+}
+
+int8_t i8atan2(int8_t y, int8_t x)
+{
+	// determine octant
+	if (y >= 0) { // oct 0,1,2,3
+		if (x >= 0) { // oct 0,1
+			if (x > y) {
+				return iat2(-y, -x) / 2 + (0 * 32);
+			} else {
+				if (y == 0) return 0; // (x=0,y=0)
+				return -iat2(-x, -y) / 2 + (2 * 32);
+			}
+		} else { // oct 2,3
+			if (x >= -y) {
+				return iat2(x, -y) / 2 + (2 * 32);
+			} else {
+				return -iat2(-y, x) / 2 + (4 * 32);
+			}
+		}
+	} else { // oct 4,5,6,7
+		if (x < 0) { // oct 4,5
+			if (x < y) {
+				return iat2(y, x) / 2 + (-4 * 32);
+			} else {
+				return -iat2(x, y) / 2 + (-2 * 32);
+			}
+		} else { // oct 6,7
+			if (-x >= y) {
+				return iat2(-x, y) / 2 + (-2 * 32);
+			} else {
+				return -iat2(y, -x) / 2 + (-0 * 32);
+			}
+		}
+	}
+}