Improve PWM on ESP8266

- Better phase updates without dropping samples
- Make second pin duty cycle always after first, even inverted

lib/ESP8266PWM/src/core_esp8266_waveform_phase.cpp

@@ -242,7 +242,7 @@ int startWaveformClockCycles_weak(uint8_t pin, uint32_t highCcys, uint32_t lowCc
       wave.mode = WaveformMode::UPDATEEXPIRY;
       std::atomic_thread_fence(std::memory_order_release);
       waveform.toSetBits = 1UL << pin;
-    } else if (alignPhase) {
+    } else if (alignPhase >= 0) {
       // @willmmiles new feature
       wave.mode = WaveformMode::UPDATEPHASE; // recalculate start
       std::atomic_thread_fence(std::memory_order_release);
@@ -303,7 +303,7 @@ static inline IRAM_ATTR int32_t scaleCcys(const int32_t ccys, const bool isCPU2X
 
 static IRAM_ATTR void timer1Interrupt() {
   const uint32_t isrStartCcy = ESP.getCycleCount();
-  int32_t clockDrift = isrStartCcy - waveform.nextEventCcy;
+  //int32_t clockDrift = isrStartCcy - waveform.nextEventCcy;
 
   // ----- @willmmiles begin patch -----
   nmiCrashWorkaround();
@@ -341,12 +341,16 @@ static IRAM_ATTR void timer1Interrupt() {
       break;
     // @willmmiles new feature
     case WaveformMode::UPDATEPHASE:
-      // in WaveformMode::UPDATEPHASE, we recalculate the targets without adjusting the state
+      // in WaveformMode::UPDATEPHASE, we recalculate the targets
       if (waveform.alignPhase >= 0 && waveform.enabled & (1UL << waveform.alignPhase)) {
+        // Compute phase shift to realign with target
         auto& align_wave = waveform.pins[waveform.alignPhase];                
-        // Go back one cycle
+        int32_t shift = static_cast<int32_t>(align_wave.nextPeriodCcy + scaleCcys(waveform.phaseCcy, isCPU2X) - wave.nextPeriodCcy);
-        wave.nextPeriodCcy = align_wave.nextPeriodCcy - scaleCcys(align_wave.periodCcys, isCPU2X) + scaleCcys(waveform.phaseCcy, isCPU2X);
+        const int32_t periodCcys = scaleCcys(wave.periodCcys, isCPU2X);
-        wave.endDutyCcy = wave.nextPeriodCcy + scaleCcys(wave.dutyCcys, isCPU2X);
+        if (shift > periodCcys/2) shift -= periodCcys;
+        else if (shift <= -periodCcys/2) shift += periodCcys;
+        wave.nextPeriodCcy += shift;
+        wave.endDutyCcy += shift;
       }
     default:
       break;
@@ -462,7 +466,7 @@ static IRAM_ATTR void timer1Interrupt() {
       }
       now = ESP.getCycleCount();
     }
-    clockDrift = 0;
+    //clockDrift = 0;
   }
 
   int32_t callbackCcys = 0;

wled00/bus_manager.cpp

@@ -565,7 +565,7 @@ void BusPwm::show() {
    const unsigned analogPeriod = F_CPU / _frequency;
    const unsigned maxBri = analogPeriod;  // compute to clock cycle accuracy
    constexpr bool dithering = false;   
-   constexpr unsigned bitShift = 7;  // 2^7 clocks for dead time
+   constexpr unsigned bitShift = 8;  // 256 clocks for dead time, ~3us at 80MHz
 #else
   // if _needsRefresh is true (UI hack) we are using dithering (credit @dedehai & @zalatnaicsongor)
   // https://github.com/Aircoookie/WLED/pull/4115 and https://github.com/zalatnaicsongor/WLED/pull/1)
@@ -609,8 +609,10 @@ void BusPwm::show() {
         duty -= deadTime << 1; // shorten duty of larger signal except if full on
       }
     }
-    if (_reversed) duty = maxBri - duty;
+    if (_reversed) {
-
+      if (i) hPoint += duty;  // align start at time zero
+      duty = maxBri - duty;
+    }
     #ifdef ESP8266
     //stopWaveform(_pins[i]);  // can cause the waveform to miss a cycle. instead we risk crossovers.
     startWaveformClockCycles(_pins[i], duty, analogPeriod - duty, 0, i ? _pins[0] : -1, hPoint, false);
@@ -625,7 +627,8 @@ void BusPwm::show() {
     ledc_update_duty((ledc_mode_t)gr, (ledc_channel_t)ch);
     #endif
     
-    hPoint += duty + (_reversed ? -1 : 1) * deadTime;        // offset to cascade the signals
+    if (!_reversed) hPoint += duty;
+    hPoint += deadTime;        // offset to cascade the signals
     if (hPoint >= maxBri) hPoint -= maxBri; // offset is out of bounds, reset
   }
 }