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Keep PWM phases constant #7057

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Keep PWM phases constant #7057

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7f2c4e9
Make sure PWM phases remain constant
s-hadinger Feb 2, 2020
64c6f04
Remove the entire waveform overshoot compensation
Feb 26, 2020
7f821ce
Avoid thrashing
s-hadinger Mar 3, 2020
d7852d2
Merge branch 'master' of https://github.com/esp8266/Arduino into patch-1
s-hadinger Apr 8, 2020
5db5df6
Better handling of interrupt storm during wifi connection
s-hadinger Apr 8, 2020
4f4b504
Better handling of interrupt storm during wifi connection
s-hadinger Apr 8, 2020
c70e835
Merge branch 'master' of https://github.com/esp8266/Arduino into patch-1
s-hadinger May 6, 2020
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36 changes: 32 additions & 4 deletions cores/esp8266/core_esp8266_waveform.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -170,6 +170,13 @@ static inline ICACHE_RAM_ATTR uint32_t min_u32(uint32_t a, uint32_t b) {
return b;
}

static inline ICACHE_RAM_ATTR int32_t max_32(int32_t a, int32_t b) {
if (a < b) {
return b;
}
return a;
}

// Stops a waveform on a pin
int ICACHE_RAM_ATTR stopWaveform(uint8_t pin) {
// Can't possibly need to stop anything if there is no timer active
Expand Down Expand Up @@ -259,23 +266,44 @@ static ICACHE_RAM_ATTR void timer1Interrupt() {
// Check for toggles
int32_t cyclesToGo = wave->nextServiceCycle - now;
if (cyclesToGo < 0) {
// See #7057
// The following is a no-op unless we have overshot by an entire waveform cycle.
// As modulus is an expensive operation, this code is removed for now:
// cyclesToGo = -((-cyclesToGo) % (wave->nextTimeHighCycles + wave->nextTimeLowCycles));
//
// Alternative version with lower CPU impact:
// 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 = ((uint32_t)-cyclesToGo) > ((wave->nextTimeHighCycles + wave->nextTimeLowCycles) >> 2);
waveformState ^= mask;
if (waveformState & mask) {
if (i == 16) {
GP16O |= 1; // GPIO16 write slow as it's RMW
} else {
SetGPIO(mask);
}
wave->nextServiceCycle = now + wave->nextTimeHighCycles;
nextEventCycles = min_u32(nextEventCycles, wave->nextTimeHighCycles);
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 = now + wave->nextTimeLowCycles;
nextEventCycles = min_u32(nextEventCycles, wave->nextTimeLowCycles);
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;
Expand Down