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PWM enhancements (phase shifting and dithering) #4115

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PWM enhancements (phase shifting and dithering) #4115

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741b76f
Adding dithering to PWM and proper phase shifting (draft)
DedeHai Aug 25, 2024
8dbba62
code cleanup
DedeHai Aug 25, 2024
718e864
Merge branch 'bus-config' into 0_15_PWM_enhancement
blazoncek Aug 26, 2024
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106 changes: 81 additions & 25 deletions wled00/bus_manager.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@
#include <IPAddress.h>
#ifdef ARDUINO_ARCH_ESP32
#include "driver/ledc.h"
#include "soc/ledc_struct.h"
#endif
#include "const.h"
#include "pin_manager.h"
Expand Down Expand Up @@ -401,33 +402,50 @@ BusPwm::BusPwm(BusConfig &bc)
{
if (!isPWM(bc.type)) return;
unsigned numPins = numPWMPins(bc.type);
#ifdef ESP8266
_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;

#ifdef ESP8266
for (_depth = MAX_BIT_WIDTH; _depth > 8; _depth--) if (((CLOCK_FREQUENCY/_frequency) >> _depth) > 0) break;
analogWriteRange((1<<_depth)-1);
analogWriteFreq(_frequency);
#else
for (unsigned i = 0; i < numPins; i++) {
uint8_t currentPin = bc.pins[i];
if (!pinManager.allocatePin(currentPin, true, PinOwner::BusPwm)) {
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deallocatePins(); return;
}
_pins[i] = currentPin; //store only after allocatePin() succeeds
pinMode(_pins[i], OUTPUT);
}
#else
_depth = 12; // set to 12bit resolution by default
unsigned ditheringbits = 4;
switch (bc.frequency) { // TODO: this is not the proper way to handle this, could just save the type instead of frequency
case WLED_PWM_FREQ/2 : _frequency = WLED_PWM_FREQ/2; break; // slow, 10kHz, 8bit + 4bit dithering
case WLED_PWM_FREQ*2/3 : _frequency = WLED_PWM_FREQ; _depth = 11; break; // medium, 20kHz, 7bit + 4bit dithering
default:
case WLED_PWM_FREQ : _frequency = WLED_PWM_FREQ*2; break; // fast, 40kHz, 8bit + 4bit dithering
case WLED_PWM_FREQ*2 : _frequency = WLED_PWM_FREQ*3; break; // ultra fast, 60kHz, 8bit + 4bit dithering
case WLED_PWM_FREQ*10/3 : _frequency = WLED_PWM_FREQ*4/3; _depth = 10; ditheringbits = 0; break; // no dithering, 26kHz, 10bit
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I am referring to this line.

}
_ledcStart = pinManager.allocateLedc(numPins);
if (_ledcStart == 255) { //no more free LEDC channels
deallocatePins(); return;
}
#endif

for (unsigned i = 0; i < numPins; i++) {
uint8_t currentPin = bc.pins[i];
if (!pinManager.allocatePin(currentPin, true, PinOwner::BusPwm)) {
deallocatePins(); return;
}
_pins[i] = currentPin; //store only after allocatePin() succeeds
#ifdef ESP8266
pinMode(_pins[i], OUTPUT);
#else
ledcSetup(_ledcStart + i, _frequency, _depth);
ledcSetup(_ledcStart + i, _frequency, _depth - ditheringbits); // TODO: if this is a CCT 2 pin strip, first channel must fulfill ch%2==0 so both use the same timer!
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ledcAttachPin(_pins[i], _ledcStart + i);
#endif
}
// sync the timers (not perfect but better than unsynced)
for (unsigned i = 0; i < numPins; i++) {
uint8_t group = ((_ledcStart + i)/8), timer = (((_ledcStart + i) / 2) % 4);
ledc_timer_rst((ledc_mode_t)group, (ledc_timer_t)timer); // reset timer so PWM channels are in sync
}
#endif
_hasRgb = hasRGB(bc.type);
_hasWhite = hasWhite(bc.type);
_hasCCT = hasCCT(bc.type);
Expand Down Expand Up @@ -496,32 +514,70 @@ uint32_t BusPwm::getPixelColor(uint16_t pix) const {
void BusPwm::show() {
if (!_valid) return;
unsigned numPins = getPins();
unsigned maxBri = (1<<_depth) - 1;
// use CIE brightness formula
unsigned maxBri = (1<<_depth); // note: not subtraciting 1 ensures full on when set to max (no gpio glitching)
unsigned scaledBri[numPins];
unsigned total_dutycycle = maxBri >> 3; // start value to get better distribution
unsigned offsetSum = 0;
[[maybe_unused]] unsigned deadtime = 0;
unsigned ditheringbits = 4;
if(_frequency == WLED_PWM_FREQ*4/3) ditheringbits = 0; // no dithering TODO: POC only, this needs to be a checkmark option or some other identifier as frequency assignment may change
if(numPins == 2) //for CCT, add some dead time to prevent overlapping (TODO: in principle this is only required on reverse polarity CCT)
{
deadtime = 2 + (3 << ditheringbits);
maxBri -= deadtime;
total_dutycycle = 0; // need accurate offset calculation
}
// use CIE brightness formula (credit @dedehai)
unsigned pwmBri = (unsigned)_bri * 100;
if(pwmBri < 2040) pwmBri = ((pwmBri << _depth) + 115043) / 230087; //adding '0.5' before division for correct rounding
else {
pwmBri += 4080;
float temp = (float)pwmBri / 29580;
temp = temp * temp * temp * (1<<_depth) - 1;
temp = temp * temp * temp * maxBri;
pwmBri = (unsigned)temp;
}
// determine phase shift POC (credit @dedehai)
[[maybe_unused]] uint32_t phaseOffset = maxBri / numPins;
// determine phase shift to distribute load (credit @dedehai)
for (unsigned i = 0; i < numPins; i++) {
scaledBri[i] = (_data[i] * pwmBri) / 255;
if (_reversed) scaledBri[i] = maxBri - scaledBri[i];
#ifdef ARDUINO_ARCH_ESP32
total_dutycycle += scaledBri[i];
#endif
}
for (unsigned i = 0; i < numPins; i++) {
unsigned scaled = (_data[i] * pwmBri) / 255;
if (_reversed) scaled = maxBri - scaled;
#ifdef ESP8266
analogWrite(_pins[i], scaled);
analogWrite(_pins[i], scaledBri[i]);
#else
if (_needsRefresh) { // hacked to determine if phase shifted PWM is requested
uint8_t group = ((_ledcStart + i) / 8), channel = ((_ledcStart + i) % 8); // _ledcStart + i is always less than MAX_LED_CHANNELS/LEDC_CHANNELS
ledc_set_duty_with_hpoint((ledc_mode_t)group, (ledc_channel_t)channel, scaled, phaseOffset*i);
ledc_update_duty((ledc_mode_t)group, (ledc_channel_t)channel);
} else
ledcWrite(_ledcStart + i, scaled);
// Calculate phase offsets to distribute signals evenly
unsigned phaseoffset = offsetSum;
if(numPins == 2) { // CCT
offsetSum = scaledBri[i] + deadtime / 2 + (maxBri - total_dutycycle) / 2; // fixed 180° out of phase
scaledBri[i] = scaledBri[i] >= maxBri ? 1 << _depth : scaledBri[i]; // scale to full on
}
else
offsetSum += (scaledBri[i]<<_depth) / total_dutycycle;
//phaseoffset = 0;// (maxBri / numPins)*i; // for debugging, can be removed
uint8_t group=((_ledcStart + i)/8), channel=((_ledcStart + i)%8);
//directly write to LEDc struct as there is no HAL exposed function for dithering. note: no checking is done (assumes correctly assigned channels)
LEDC.channel_group[group].channel[channel].duty.duty = scaledBri[i] << (4 - ditheringbits);
LEDC.channel_group[group].channel[channel].hpoint.hpoint = phaseoffset >> ditheringbits; // offset works with MSBs only
ledc_update_duty((ledc_mode_t)group, (ledc_channel_t)channel);
/*
// debug output, can be removed
Serial.print("IO");
Serial.print(_pins[i]);
Serial.print("\t group:");
Serial.print(group);
Serial.print("\t CH");
Serial.print(channel);
Serial.print("\t duty: ");
Serial.print(scaledBri[i]);
Serial.print("\t offset: ");
Serial.println(phaseoffset);
*/
#endif
}
// Serial.println("***");
}

uint8_t BusPwm::getPins(uint8_t* pinArray) const {
Expand Down