From ca70b50e4901c20290d37aef87062c0e8c94c854 Mon Sep 17 00:00:00 2001
From: Tangent Wantwight <tangent128@gmail.com>
Date: Wed, 2 Oct 2024 21:10:58 -0400
Subject: [PATCH] attempt to deglitch lights. dubious.

---
 itsybitsy_m0_lights/src/lib.rs | 94 ++++++++++++++++++++++++----------
 1 file changed, 68 insertions(+), 26 deletions(-)

diff --git a/itsybitsy_m0_lights/src/lib.rs b/itsybitsy_m0_lights/src/lib.rs
index 5fcc919..2888d1f 100644
--- a/itsybitsy_m0_lights/src/lib.rs
+++ b/itsybitsy_m0_lights/src/lib.rs
@@ -63,43 +63,85 @@ where
 {
     #[inline]
     pub fn write(&mut self, bit: bool) {
-        // go high
-        self.high_out.set_high().unwrap();
-
-        // experimentally, there is some unknown overhead
-        // but these timings appear to work for me
-        unsafe {
-            compiler_fence(Ordering::SeqCst);
-            asm!(
-                // 8 nops
-                "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;",
-            );
-            compiler_fence(Ordering::SeqCst);
-        }
-
         if bit {
             unsafe {
+                compiler_fence(Ordering::SeqCst);
+                self.high_out.set_high().unwrap();
                 compiler_fence(Ordering::SeqCst);
                 asm!(
-                    // 14 nops
+                    // 15 nops
                     "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;",
-                    "nop;", "nop;", "nop;", "nop;",
+                    "nop;", "nop;", "nop;", "nop;", "nop;",
+                );
+                compiler_fence(Ordering::SeqCst);
+                self.high_out.set_low().unwrap();
+                compiler_fence(Ordering::SeqCst);
+                asm!(
+                    // 8 nops
+                    "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;",
+                );
+                compiler_fence(Ordering::SeqCst);
+            }
+        } else {
+            unsafe {
+                compiler_fence(Ordering::SeqCst);
+                self.high_out.set_high().unwrap();
+                compiler_fence(Ordering::SeqCst);
+                asm!(
+                    // 8 nops
+                    "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;",
+                );
+                compiler_fence(Ordering::SeqCst);
+                self.high_out.set_low().unwrap();
+                compiler_fence(Ordering::SeqCst);
+                asm!(
+                    // 15 nops
+                    "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;",
+                    "nop;", "nop;", "nop;", "nop;", "nop;",
                 );
                 compiler_fence(Ordering::SeqCst);
             }
         }
 
-        // go low
-        self.high_out.set_low().unwrap();
+        if false {
+            // go high
+            self.high_out.set_high().unwrap();
 
-        unsafe {
-            compiler_fence(Ordering::SeqCst);
-            asm!(
-                // 15 nops
-                "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;",
-                "nop;", "nop;", "nop;", "nop;", "nop;",
-            );
-            compiler_fence(Ordering::SeqCst);
+            // experimentally, there is some unknown overhead
+            // but these timings appear to work for me
+            unsafe {
+                compiler_fence(Ordering::SeqCst);
+                asm!(
+                    // 8 nops
+                    "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;",
+                );
+                compiler_fence(Ordering::SeqCst);
+            }
+
+            if bit {
+                unsafe {
+                    compiler_fence(Ordering::SeqCst);
+                    asm!(
+                        // 14 nops
+                        "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;",
+                        "nop;", "nop;", "nop;", "nop;", "nop;",
+                    );
+                    compiler_fence(Ordering::SeqCst);
+                }
+            }
+
+            // go low
+            self.high_out.set_low().unwrap();
+
+            unsafe {
+                compiler_fence(Ordering::SeqCst);
+                asm!(
+                    // 15 nops
+                    "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;",
+                    "nop;", "nop;", "nop;", "nop;", "nop;",
+                );
+                compiler_fence(Ordering::SeqCst);
+            }
         }
     }