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Merge pull request #4126 from DedeHai/PWM-fixes

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fixed offsets and inverted signal plus dead time
This commit is contained in:
Blaž Kristan 2024-09-05 17:26:28 +02:00 committed by GitHub
commit 55d98ff935
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1 changed files with 36 additions and 37 deletions
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73
wled00/bus_manager.cpp
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@ -410,6 +410,7 @@ BusPwm::BusPwm(BusConfig &bc)
{
if (!isPWM(bc.type)) return;
unsigned numPins = numPWMPins(bc.type);
unsigned dithering = 0;
_frequency = bc.frequency ? bc.frequency : WLED_PWM_FREQ;
// duty cycle resolution (_depth) can be extracted from this formula: CLOCK_FREQUENCY > _frequency * 2^_depth
for (_depth = MAX_BIT_WIDTH; _depth > 8; _depth--) if (((CLOCK_FREQUENCY/_frequency) >> _depth) > 0) break;
@ -428,7 +429,11 @@ BusPwm::BusPwm(BusConfig &bc)
pinManager.deallocateMultiplePins(pins, numPins, PinOwner::BusPwm);
return;
}
if (_needsRefresh) _depth = 8; // fixed 8 bit depth with 4 bit dithering (ESP8266 has no hardware to support dithering)
// if _needsRefresh is true (UI hack) we are using dithering (credit @dedehai & @zalatnaicsongor)
if (_needsRefresh) {
_depth = 12; // fixed 8 bit depth PWM with 4 bit dithering (ESP8266 has no hardware to support dithering)
dithering = 4;
}
#endif
for (unsigned i = 0; i < numPins; i++) {
@ -437,7 +442,7 @@ BusPwm::BusPwm(BusConfig &bc)
pinMode(_pins[i], OUTPUT);
#else
unsigned channel = _ledcStart + i;
ledcSetup(channel, _frequency, _depth);
ledcSetup(channel, _frequency, _depth - dithering);
ledcAttachPin(_pins[i], channel);
// LEDC timer reset credit @dedehai
uint8_t group = (channel / 8), timer = ((channel / 2) % 4); // same fromula as in ledcSetup()
@ -511,8 +516,12 @@ uint32_t BusPwm::getPixelColor(uint16_t pix) const {
void BusPwm::show() {
if (!_valid) return;
// 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)
const bool dithering = _needsRefresh; // avoid working with bitfield
const unsigned numPins = getPins();
const unsigned maxBri = (1<<_depth); // possible values: 16384 (14), 8192 (13), 4096 (12), 2048 (11), 1024 (10), 512 (9) and 256 (8)
const unsigned maxBri = (1<<_depth); // possible values: 16384 (14), 8192 (13), 4096 (12), 2048 (11), 1024 (10), 512 (9) and 256 (8)
const unsigned bitShift = dithering * 4; // if dithering, _depth is 12 bit but LEDC channel is set to 8 bit (using 4 fractional bits)
// use CIE brightness formula (cubic) to fit (or approximate linearity of) human eye perceived brightness
// the formula is based on 12 bit resolution as there is no need for greater precision
@ -525,52 +534,42 @@ void BusPwm::show() {
// cubic response for values [21-255]
pwmBri += 4080;
float temp = (float)pwmBri / 29580.0f;
temp = temp * temp * temp * 4095.0f;
pwmBri = (unsigned)temp;
temp = temp * temp * temp * (float)maxBri;
pwmBri = (unsigned)temp; // pwmBri is in range [0-maxBri]
}
// pwmBri is in range [0-4095]
// determine phase shift
[[maybe_unused]] unsigned phaseOffset = maxBri / numPins; // (maxBri is at _depth resolution)
// we will be phase shifting every channel by fixed amount (i times /2 or /3 or /4 or /5)
// phase shifting is only mandatory when using H-bridge to drive reverse-polarity PWM CCT (2 wire) LED type (with 180° phase)
// CCT additive blending must be 0 (WW & CW must not overlap) in such case
[[maybe_unused]] unsigned hPoint = 0; // phase shift (0 - maxBri)
// we will be phase shifting every channel by previous pulse length (plus dead time if required)
// phase shifting is only mandatory when using H-bridge to drive reverse-polarity PWM CCT (2 wire) LED type
// CCT additive blending must be 0 (WW & CW will not overlap) otherwise signals *will* overlap
// for all other cases it will just try to "spread" the load on PSU
[[maybe_unused]] bool cctOverlap = (_type == TYPE_ANALOG_2CH) && (_data[0]+_data[1] >= 254);
// 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)
bool dithering = _needsRefresh; // avoid working with bitfield
// Phase shifting requires that LEDC timers are synchronised (see setup()). For PWM CCT (and H-bridge) it is
// also mandatory that both channels use the same timer (pinManager takes care of that).
for (unsigned i = 0; i < numPins; i++) {
unsigned scaled = (_data[i] * pwmBri) / 255; // scaled is at 12 bit depth (same as pwmBri)
// adjust "scaled" value (to fit resolution bounds)
if (_depth < 12 && !dithering) scaled >>= 12 - _depth; // normalize scaled value (if not using dithering)
else if (_depth > 12) scaled <<= _depth - 12; // scale to _depth if using >12 bit
if (_reversed) scaled = maxBri - scaled;
// scaled is now at _depth resolution (8-14 bits) except when using dithering, 12 bit in such case
unsigned duty = (_data[i] * pwmBri) / 255;
#ifdef ESP8266
analogWrite(_pins[i], scaled);
if (_reversed) duty = maxBri - duty;
analogWrite(_pins[i], duty);
#else
unsigned channel = _ledcStart + i;
// prevent overlapping PWM signals for H-bridge
// pinManager will make sure both LEDC channels are in the same speed group and sharing the same timer
// so we only need to take care of shortening the signal at 50% distribution for 1 pulse
if (cctOverlap && Bus::getCCTBlend() == 0) {
unsigned shift = (dithering*4);
unsigned briLimit = phaseOffset << shift; // expand limit if using dithering
if (scaled >= briLimit) scaled = briLimit - (1<<shift); // safety check & 1 pulse dead time when brightness is at 50%
int deadTime = 0;
if (_type == TYPE_ANALOG_2CH && Bus::getCCTBlend() == 0) {
// add dead time between signals (when using dithering, two full 8bit pulses are required)
deadTime = (1+dithering) << bitShift;
// we only need to take care of shortening the signal at (almost) full brightness otherwise pulses may overlap
if (_bri >= 254 && duty >= maxBri / 2 && duty < maxBri) duty -= deadTime << 1; // shorten duty of larger signal except if full on
if (_reversed) deadTime = -deadTime; // need to invert dead time to make phaseshift go the opposite way so low signals dont overlap
}
if (_reversed) duty = maxBri - duty;
unsigned channel = _ledcStart + i;
unsigned gr = channel/8; // high/low speed group
unsigned ch = channel%8; // group channel
// directly write to LEDC struct as there is no HAL exposed function for dithering
// duty has 20 bit resolution with 4 fractional bits (24 bits in total)
// _depth is 8 bit in this case (and maxBri==256), scaled is still at 12 bit
LEDC_MUTEX_LOCK();
LEDC.channel_group[gr].channel[ch].duty.duty = scaled << ((!dithering)*4); // write full 12 bit value (4 dithering bits)
LEDC.channel_group[gr].channel[ch].hpoint.hpoint = phaseOffset*i; // phaseOffset is at _depth resolution (8 bit)
LEDC_MUTEX_UNLOCK();
LEDC.channel_group[gr].channel[ch].duty.duty = duty << ((!dithering)*4); // lowest 4 bits are used for dithering, shift by 4 bits if not using dithering
LEDC.channel_group[gr].channel[ch].hpoint.hpoint = hPoint >> bitShift; // hPoint is at _depth resolution (needs shifting if dithering)
ledc_update_duty((ledc_mode_t)gr, (ledc_channel_t)ch);
hPoint += duty + deadTime; // offset to cascade the signals
if (hPoint >= maxBri) hPoint = 0; // offset it out of bounds, reset
#endif
}
}