Carry over a few insights from comparing to original waveform (phase-sync) branch.

Author: dok-net

cores/esp8266/core_esp8266_waveform.cpp

@@ -41,7 +41,6 @@
 
 #include "core_esp8266_waveform.h"
 #include <Arduino.h>
-#include "debug.h"
 #include "ets_sys.h"
 #include <atomic>
 
@@ -150,7 +149,7 @@ static void initTimer() {
   timer1_write(IRQLATENCYCCYS); // Cause an interrupt post-haste
 }
 
-static void IRAM_ATTR deinitIdleTimer() {
+static IRAM_ATTR void deinitIdleTimer() {
   if (!waveform.timer1Running || waveform.enabled || waveform.timer1CB || pwmState.cnt) {
     return;
   }
@@ -174,8 +173,9 @@ extern "C" {
 // Wait for mailbox to be emptied (either busy or delay() as needed)
 static IRAM_ATTR void _notifyPWM(PWMState *p, bool idle) {
   p->pwmUpdate = nullptr;
-  pwmState.pwmUpdate = p;
   std::atomic_thread_fence(std::memory_order_release);
+  pwmState.pwmUpdate = p;
+  std::atomic_thread_fence(std::memory_order_acq_rel);
   if (idle) {
     forceTimerTrigger();
   }

cores/esp8266/core_esp8266_waveform.h

@@ -56,9 +56,8 @@ extern "C" {
 // Setting autoPwm to true allows the wave generator to maintain PWM duty to idle cycle ratio
 // under load, for applications where frequency or duty cycle must not change, leave false.
 // Returns true or false on success or failure.
-int startWaveform(uint8_t pin, uint32_t timeHighUS, uint32_t timeLowUS, uint32_t runTimeUS = 0,
-                  // Following parameters are ignored unless in PhaseLocked mode
-                  int8_t alignPhase = -1, uint32_t phaseOffsetUS = 0, bool autoPwm = false);
+int startWaveform(uint8_t pin, uint32_t timeHighUS, uint32_t timeLowUS,
+  uint32_t runTimeUS = 0, int8_t alignPhase = -1, uint32_t phaseOffsetUS = 0, bool autoPwm = false);
 
 // Start or change a waveform of the specified high and low CPU clock cycles on specific pin.
 // If runtimeCycles > 0 then automatically stop it after that many CPU clock cycles, relative to the next
@@ -68,9 +67,8 @@ int startWaveform(uint8_t pin, uint32_t timeHighUS, uint32_t timeLowUS, uint32_t
 // Setting autoPwm to true allows the wave generator to maintain PWM duty to idle cycle ratio
 // under load, for applications where frequency or duty cycle must not change, leave false.
 // Returns true or false on success or failure.
-int startWaveformClockCycles(uint8_t pin, uint32_t timeHighCcys, uint32_t timeLowCcys, uint32_t runTimeCcys = 0,
-                  // Following parameters are ignored unless in PhaseLocked mode
-                  int8_t alignPhase = -1, uint32_t phaseOffsetCcys = 0, bool autoPwm = false);
+int startWaveformClockCycles(uint8_t pin, uint32_t timeHighCcys, uint32_t timeLowCcys,
+  uint32_t runTimeCcys = 0, int8_t alignPhase = -1, uint32_t phaseOffsetCcys = 0, bool autoPwm = false);
 
 // Stop a waveform, if any, on the specified pin.
 // Returns true or false on success or failure.

cores/esp8266/core_esp8266_wiring_pwm.cpp

@@ -58,7 +58,6 @@ extern void __analogWriteMode(uint8_t pin, int val, bool openDrain) {
   if (pin > 16) {
     return;
   }
-  uint32_t analogPeriod = microsecondsToClockCycles(1000000UL) / analogFreq;
   if (val < 0) {
     val = 0;
   } else if (val > analogScale) {
@@ -75,28 +74,14 @@ extern void __analogWriteMode(uint8_t pin, int val, bool openDrain) {
   else {
     pinMode(pin, openDrain ? OUTPUT_OPEN_DRAIN : OUTPUT);
   }
-  uint32_t high = (analogPeriod * val) / analogScale;
-  uint32_t low = analogPeriod - high;
-  // Find the first GPIO being generated by checking GCC's find-first-set (returns 1 + the bit of the first 1 in an int32_t)
-  int phaseReference = __builtin_ffs(analogMap) - 1;
+  
   // Per the Arduino docs at https://www.arduino.cc/reference/en/language/functions/analog-io/analogwrite/
   // val: the duty cycle: between 0 (always off) and 255 (always on).
   // So if val = 0 we have digitalWrite(LOW), if we have val==range we have digitalWrite(HIGH)
   if (_setPWM(pin, val, analogScale)) {
     if (val > 0 && val < analogScale) {
       analogMap |= (1 << pin);
     }
-  } else {
-    const bool detach = (val == 0 || val == analogScale);
-    // To go steady LOW or HIGH, let the waveform run into next duty cycle, if any. Then stop.
-    if (startWaveformClockCycles(pin, high, low, static_cast<uint32_t>(detach), phaseReference, 0, true)) {
-      if (detach) {
-        delay((1000 + analogFreq) / analogFreq);
-        stopWaveform(pin);
-      } else {
-        analogMap |= (1 << pin);
-      }
-    }
   }
 }