From a9cdd21da90bca5f364e2694acde1f59143a65de Mon Sep 17 00:00:00 2001
From: Frank <frank.moehle@outlook.de>
Date: Mon, 12 Jun 2023 23:27:09 +0200
Subject: [PATCH] prevent strip flickering

* it seems that NPB is very sensitive when being interrupted during LEDs driving.  This change tries to avoid flash (file) writes when the strip is active.
* minor optimization: yield is completely unnecessary on ESP32 (we have a real OS).
---
 wled00/fcn_declare.h |  2 ++
 wled00/presets.cpp   | 14 ++++++++++++++
 wled00/wled.cpp      | 20 ++++++++++++++++++++
 3 files changed, 36 insertions(+)

diff --git a/wled00/fcn_declare.h b/wled00/fcn_declare.h
index ad6fe6ea..98f95caa 100644
--- a/wled00/fcn_declare.h
+++ b/wled00/fcn_declare.h
@@ -199,6 +199,8 @@ void handlePlaylist();
 void serializePlaylist(JsonObject obj);
 
 //presets.cpp
+bool presetsSavePending(void);    // WLEDMM true if presetToSave, playlistSave or saveLedmap
+bool presetsActionPending(void);  // WLEDMM true if presetToApply, presetToSave, playlistSave or saveLedmap
 void initPresetsFile();
 void handlePresets();
 bool applyPreset(byte index, byte callMode = CALL_MODE_DIRECT_CHANGE);
diff --git a/wled00/presets.cpp b/wled00/presets.cpp
index abcc4e79..b293bb2e 100644
--- a/wled00/presets.cpp
+++ b/wled00/presets.cpp
@@ -20,6 +20,20 @@ static const char *getFileName(bool persist = true) {
   return persist ? "/presets.json" : "/tmp.json";
 }
 
+bool presetsSavePending(void) {  // WLEDMM true if presetToSave, playlistSave or saveLedmap
+  if (presetToSave > 0) return(true);
+  if (playlistSave == true) return(true);
+  if (saveLedmap >= 0) return(true);
+  return(false);
+}
+bool presetsActionPending(void) {  // WLEDMM true if presetToApply, presetToSave, playlistSave or saveLedmap
+  if (presetToApply > 0) return(true);
+  if (presetToSave > 0) return(true);
+  if (playlistSave == true) return(true);
+  if (saveLedmap >= 0) return(true);
+  return(false);
+}
+
 static void doSaveState() {
   bool persist = (presetToSave < 251);
   const char *filename = getFileName(persist);
diff --git a/wled00/wled.cpp b/wled00/wled.cpp
index 6521e3f5..c61b12b0 100644
--- a/wled00/wled.cpp
+++ b/wled00/wled.cpp
@@ -87,6 +87,10 @@ void WLED::reset()
   ESP.restart();
 }
 
+#if defined(ARDUINO_ARCH_ESP32) && defined(WLEDMM_FASTPATH)
+#define yield() {}  // WLEDMM yield() is completely unnecessary on esp32. See https://github.com/espressif/arduino-esp32/issues/1385
+#endif
+
 void WLED::loop()
 {
   #ifdef WLED_DEBUG
@@ -141,6 +145,18 @@ void WLED::loop()
 
   yield();
 
+  // https://github.com/Makuna/NeoPixelBus/wiki/ESP32-and-RTOS-Tasks
+  // On ESP32, when the CPU is loaded, asynchronous WiFi libraries (like ESPAsyncWebServer or async-mqtt-client) may interfere with interrupts used to control the LEDs (I2S mode is less affected by this), 
+  // which causes flickering of LEDs.
+  #if defined(ARDUINO_ARCH_ESP32) && (defined(WLEDMM_FASTPATH) || defined(WLEDMM_PROTECT_SERVICE))  // WLEDMM experimental: avoid strip flickering
+  #define FILEWRITE_MAX_WAIT_MS 30  // max time for waiting - aligned with 33 fps
+  //if (doReboot || doSerializeConfig || doCloseFile || loadLedmap || presetsActionPending()) {     // WLEDMM trx this to also wait before reading from files
+  if (doReboot || doSerializeConfig || doCloseFile || presetsSavePending()) {                       // WLEDMM wait until strip gets idle before writing to files
+    unsigned long waitStripStart = millis();
+    while (strip.isUpdating() && (millis() - waitStripStart < FILEWRITE_MAX_WAIT_MS)) {delay(3);}
+  }
+  #endif
+
   if (doSerializeConfig) serializeConfig();
 
   if (doReboot && !doInitBusses) // if busses have to be inited & saved, wait until next iteration
@@ -340,6 +356,10 @@ void WLED::loop()
 #endif
 }
 
+#if defined(ARDUINO_ARCH_ESP32) && defined(WLEDMM_FASTPATH)
+#undef yield  // WLEDMM restore yield()
+#endif
+
 void WLED::enableWatchdog() {
 #if WLED_WATCHDOG_TIMEOUT > 0
 #ifdef ARDUINO_ARCH_ESP32