From c4d9c4a2c5daa17756f8bb6fdbb4e15362879bef Mon Sep 17 00:00:00 2001
From: Rodrigo Alfonso <rodri042@gmail.com>
Date: Tue, 11 Feb 2025 20:58:51 -0300
Subject: [PATCH] FIX: Making IR demodulation more reliable using
 DEMODULATION_HYSTERESIS_DELAY

---
 lib/LinkIR.hpp            |  1 +
 lib/iwram_code/LinkIR.cpp | 38 ++++++++++++++++++++++++++------------
 2 files changed, 27 insertions(+), 12 deletions(-)

diff --git a/lib/LinkIR.hpp b/lib/LinkIR.hpp
index efe8c24..4410e1a 100644
--- a/lib/LinkIR.hpp
+++ b/lib/LinkIR.hpp
@@ -71,6 +71,7 @@ class LinkIR {
   static constexpr int DEMODULATION_SPACE_PERIODS = 3;
   static constexpr int DEMODULATION_SPACE_THRESHOLD =
       DEMODULATION_38KHZ_PERIOD * DEMODULATION_SPACE_PERIODS;
+  static constexpr int DEMODULATION_HYSTERESIS_DELAY = 10;
   static constexpr int NEC_TOLERANCE_PERCENTAGE = 15;
   static constexpr int NEC_TOTAL_PULSES = 68;
   static constexpr int NEC_LEADER_MARK = 9000;
diff --git a/lib/iwram_code/LinkIR.cpp b/lib/iwram_code/LinkIR.cpp
index 333fa62..c5c5152 100644
--- a/lib/iwram_code/LinkIR.cpp
+++ b/lib/iwram_code/LinkIR.cpp
@@ -33,6 +33,9 @@ LINK_CODE_IWRAM bool LinkIR::receive(u16 pulses[],
   u32 pulseIndex = 0;
   u32 lastTransitionTime = 0;
 
+  bool candidateTransitionActive = false;
+  u32 candidateTransitionStart = 0;
+
   firstLightTime = 0;
   lastLightTime = 0;
   transitionCount = 0;
@@ -62,18 +65,29 @@ LINK_CODE_IWRAM bool LinkIR::receive(u16 pulses[],
       hasStarted = true;
     }
 
-    if (hasStarted && isMark &&
-        timeSinceLastLight >=
-            DEMODULATION_SPACE_THRESHOLD * CYCLES_PER_MICROSECOND) {
-      // mark -> space
-      u32 pulseDuration =
-          (currentLastLightTime - lastTransitionTime) / CYCLES_PER_MICROSECOND;
-      pulses[pulseIndex++] = pulseDuration;
-      if (pulseIndex >= maxEntries - 1)
-        break;
-      isMark = false;
-      lastTransitionTime = currentLastLightTime;
-      transitionCount = 0;
+    if (hasStarted && isMark) {
+      if (timeSinceLastLight >=
+          DEMODULATION_SPACE_THRESHOLD * CYCLES_PER_MICROSECOND) {
+        // mark -> space?
+        if (!candidateTransitionActive) {
+          candidateTransitionActive = true;
+          candidateTransitionStart = now;
+        } else if (now - candidateTransitionStart >=
+                   DEMODULATION_HYSTERESIS_DELAY * CYCLES_PER_MICROSECOND) {
+          // mark -> space (confirmed after hysteresis delay)
+          u32 pulseDuration = (currentLastLightTime - lastTransitionTime) /
+                              CYCLES_PER_MICROSECOND;
+          pulses[pulseIndex++] = pulseDuration;
+          if (pulseIndex >= maxEntries - 1)
+            break;
+          isMark = false;
+          lastTransitionTime = currentLastLightTime;
+          transitionCount = 0;
+          candidateTransitionActive = false;
+        }
+      } else {
+        candidateTransitionActive = false;
+      }
     }
 
     // Timeouts