From 3cb7fc1a5795c5e5fa49adb18d05ac1092e9c07f Mon Sep 17 00:00:00 2001
From: Tangent Wantwight <tangent128@gmail.com>
Date: Mon, 5 Jul 2021 01:22:59 -0400
Subject: [PATCH] Fix timings for solid output

---
 itsybitsy_m0_lights/src/lib.rs | 18 +++++++-----------
 1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/itsybitsy_m0_lights/src/lib.rs b/itsybitsy_m0_lights/src/lib.rs
index e8ffef8..66b3b6c 100644
--- a/itsybitsy_m0_lights/src/lib.rs
+++ b/itsybitsy_m0_lights/src/lib.rs
@@ -39,19 +39,13 @@ pub fn boot() -> NeopixelLights<
     }
 }
 
-// WS2815 lighting times
+// WS2815 ideal lighting times
 // approx. 20ns per clock cycle;
 // const ZERO_HIGH_CYCLES: u32 = 11; // about 220ns
 // const ONE_HIGH_CYCLES: u32 = 29; // about 580ns
 // const ZERO_LOW_CYCLES: u32 = 29; // about 580ns
 // const ONE_LOW_CYCLES: u32 = 11; // about 220ns
 
-// experimentally, there is some unknown overhead
-// but these timings appear to work for me:
-const ZERO_HIGH_CYCLES: u32 = 2;
-const ONE_HIGH_CYCLES: u32 = 9;
-const ZERO_LOW_CYCLES: u32 = 10;
-const ONE_LOW_CYCLES: u32 = 10;
 const LATCH_CYCLES: u32 = 15000; // about 300us
 
 pub struct NeopixelLights<T: OutputPin, U: OutputPin, V: OutputPin> {
@@ -72,11 +66,13 @@ where
         // 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!(
-                // ? nops
-                "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;",
+                // 8 nops
+                "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;",
             );
             compiler_fence(Ordering::SeqCst);
         }
@@ -85,7 +81,7 @@ where
             unsafe {
                 compiler_fence(Ordering::SeqCst);
                 asm!(
-                    // 7 nops
+                    // 14 nops
                     "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;",
                     "nop;", "nop;", "nop;", "nop;",
                 );
@@ -99,7 +95,7 @@ where
         unsafe {
             compiler_fence(Ordering::SeqCst);
             asm!(
-                // 2 nops
+                // 15 nops
                 "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;", "nop;",
                 "nop;", "nop;", "nop;", "nop;", "nop;",
             );