From 11746d942ef85f7c3d2ed14614d70e32dd112d27 Mon Sep 17 00:00:00 2001
From: Stephan Hadinger <stephan.hadinger@gmail.com>
Date: Tue, 7 Apr 2020 22:18:29 +0200
Subject: [PATCH] Fix PWM flickering during wifi connection (#8046)

---
 tasmota/CHANGELOG.md              |  1 +
 tasmota/core_esp8266_waveform.cpp | 24 +++++++++++++++++++-----
 2 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/tasmota/CHANGELOG.md b/tasmota/CHANGELOG.md
index d22c9a4c9..93e94a6c9 100644
--- a/tasmota/CHANGELOG.md
+++ b/tasmota/CHANGELOG.md
@@ -14,6 +14,7 @@
 - Add command ``SetOption91 1`` to enable fading at startup / power on
 - Add command ``SetOption41 <x>`` to force sending gratuitous ARP every <x> seconds
 - Add quick wifi reconnect using saved AP parameters when ``SetOption56 0`` (#3189)
+- Fix PWM flickering during wifi connection (#8046)
 
 ### 8.2.0.2 20200328
 
diff --git a/tasmota/core_esp8266_waveform.cpp b/tasmota/core_esp8266_waveform.cpp
index 0e4beeef2..a35bb7c84 100644
--- a/tasmota/core_esp8266_waveform.cpp
+++ b/tasmota/core_esp8266_waveform.cpp
@@ -274,7 +274,11 @@ static ICACHE_RAM_ATTR void timer1Interrupt() {
           // cyclesToGo = -((-cyclesToGo) % (wave->nextTimeHighCycles + wave->nextTimeLowCycles));
           //
           // Alternative version with lower CPU impact:
-          // while (-cyclesToGo > wave->nextTimeHighCycles + wave->nextTimeLowCycles) { cyclesToGo += wave->nextTimeHighCycles + wave->nextTimeLowCycles)};
+          // while (-cyclesToGo > wave->nextTimeHighCycles + wave->nextTimeLowCycles) { cyclesToGo += wave->nextTimeHighCycles + wave->nextTimeLowCycles); }
+          //
+          // detect interrupt storm, for example during wifi connection.
+          // if we overshoot the cycle by more than 25%, we forget phase and keep PWM duration
+          int32_t overshoot = (-cyclesToGo) > ((wave->nextTimeHighCycles + wave->nextTimeLowCycles) >> 2);
           waveformState ^= mask;
           if (waveformState & mask) {
             if (i == 16) {
@@ -282,16 +286,26 @@ static ICACHE_RAM_ATTR void timer1Interrupt() {
             } else {
               SetGPIO(mask);
             }
-            wave->nextServiceCycle += wave->nextTimeHighCycles;
-            nextEventCycles = min_u32(nextEventCycles, max_32(wave->nextTimeHighCycles + cyclesToGo, microsecondsToClockCycles(1)));
+            if (overshoot) {
+              wave->nextServiceCycle = now + wave->nextTimeHighCycles;
+              nextEventCycles = min_u32(nextEventCycles, wave->nextTimeHighCycles);
+            } else {
+              wave->nextServiceCycle += wave->nextTimeHighCycles;
+              nextEventCycles = min_u32(nextEventCycles, max_32(wave->nextTimeHighCycles + cyclesToGo, microsecondsToClockCycles(1)));
+            }
           } else {
             if (i == 16) {
               GP16O &= ~1; // GPIO16 write slow as it's RMW
             } else {
               ClearGPIO(mask);
             }
-            wave->nextServiceCycle += wave->nextTimeLowCycles;
-            nextEventCycles = min_u32(nextEventCycles, max_32(wave->nextTimeLowCycles + cyclesToGo, microsecondsToClockCycles(1)));
+            if (overshoot) {
+              wave->nextServiceCycle = now + wave->nextTimeLowCycles;
+              nextEventCycles = min_u32(nextEventCycles, wave->nextTimeLowCycles);
+            } else {
+              wave->nextServiceCycle += wave->nextTimeLowCycles;
+              nextEventCycles = min_u32(nextEventCycles, max_32(wave->nextTimeLowCycles + cyclesToGo, microsecondsToClockCycles(1)));
+            }
           }
         } else {
           uint32_t deltaCycles = wave->nextServiceCycle - now;