added optional usePhaseShift parameter to HardwarePWM constructor. …

…This uses the esp32 ledc hpoint setting to stagger the starting point of pwm channels evenly across the pwm period to improve EMI of multi-channel high current PWM applications
SmingHub · pljakobs · May 8, 2025 · May 13, 2025 · May 9, 2025 · da69d825d3f51af4eac9ddf465a8c970285f381e
commit da69d825d3f51af4eac9ddf465a8c970285f381e
diff --git a/Sming/Arch/Esp32/Core/HardwarePWM.cpp b/Sming/Arch/Esp32/Core/HardwarePWM.cpp
@@ -135,16 +135,32 @@ uint32_t maxDuty(ledc_timer_bit_t bits)
 {
 	return (1U << bits) - 1;
 }
+int hpointForPin(uint8_t channelIndex, uint8_t channel_count)
+{
+/*
+	debug_i("calculating hpoint for channel: %d\n", channelIndex);
+	debug_i("            channel_count    : %d\n", channel_count);
+	debug_i("            maxDuty           : %d\n", maxDuty(DEFAULT_RESOLUTION));
+*/
+	int _hpoint=maxDuty(DEFAULT_RESOLUTION) * channelIndex / channel_count;
+//	debug_i("hpoint is %d\n", _hpoint);
+	return _hpoint;	
+}
 
 } //namespace
 
-HardwarePWM::HardwarePWM(const uint8_t* pins, uint8_t no_of_pins) : channel_count(no_of_pins)
+HardwarePWM::HardwarePWM(const uint8_t* pins, uint8_t no_of_pins, bool usePhaseShift ) : channel_count(no_of_pins)
 {
 	assert(no_of_pins > 0 && no_of_pins <= SOC_LEDC_CHANNEL_NUM);
 	no_of_pins = std::min(uint8_t(SOC_LEDC_CHANNEL_NUM), no_of_pins);
 
+	_usePhaseShift = usePhaseShift;
 	periph_module_enable(PERIPH_LEDC_MODULE);
 
+	if (_usePhaseShift) {
+		debug_i("Using phase shift for %d channels\n", no_of_pins);
+	}
+
 	for(uint8_t i = 0; i < no_of_pins; i++) {
 		channels[i] = pins[i];
 
@@ -181,7 +197,7 @@ HardwarePWM::HardwarePWM(const uint8_t* pins, uint8_t no_of_pins) : channel_coun
 			.intr_type = LEDC_INTR_DISABLE,
 			.timer_sel = pinToTimer(i),
 			.duty = 0,
-			.hpoint = 0,
+			.hpoint = _usePhaseShift?hpointForPin(i,channel_count):0,
 		};
 		debug_d("ledc_channel\n"
 				"\tspeed_mode: %i\r\n"
@@ -191,7 +207,7 @@ HardwarePWM::HardwarePWM(const uint8_t* pins, uint8_t no_of_pins) : channel_coun
 				"\tgpio_num: %i\r\n"
 				"\tduty: %i\r\n"
 				"\thpoint: %i\r\n\n",
-				pinToGroup(i), pinToChannel(i), pinToTimer(i), ledc_channel.intr_type, pins[i], 0, 0);
+				pinToGroup(i), pinToChannel(i), pinToTimer(i), ledc_channel.intr_type, pins[i], 0, _usePhaseShift?hpointForPin(i,channel_count):0);
 		ESP_ERROR_CHECK(ledc_channel_config(&ledc_channel));
 		ledc_bind_channel_timer(pinToGroup(i), pinToChannel(i), pinToTimer(i));
 	}
@@ -247,7 +263,11 @@ void HardwarePWM::setPeriod(uint32_t period)
 	// Set the frequency globally, will add per timer functions later.
 	// Also, this can be done smarter.
 	for(uint8_t i = 0; i < channel_count; i++) {
-		ESP_ERROR_CHECK(ledc_set_freq(pinToGroup(i), pinToTimer(i), periodToFrequency(period)));
+		if(_usePhaseShift){
+			ESP_ERROR_CHECK(ledc_set_duty_with_hpoint(pinToGroup(i), pinToChannel(i), period, hpointForPin(i,channel_count)));
+		}else{
+			ESP_ERROR_CHECK(ledc_set_freq(pinToGroup(i), pinToTimer(i), periodToFrequency(period)));
+		}
 	}
 	// ledc_update_duty();
 	update();

diff --git a/Sming/Arch/Esp8266/Core/HardwarePWM.cpp b/Sming/Arch/Esp8266/Core/HardwarePWM.cpp
@@ -52,7 +52,7 @@ static const uint8_t gpioPinFunc[]{
 	FUNC_GPIO15, //
 };
 
-HardwarePWM::HardwarePWM(const uint8_t* pins, uint8_t noOfPins) : channel_count(noOfPins)
+HardwarePWM::HardwarePWM(const uint8_t* pins, uint8_t no_of_pins, bool usePhaseShift ) : channel_count(no_of_pins)
 {
 	if(noOfPins == 0) {
 		return;

diff --git a/Sming/Arch/Host/Core/HardwarePWM.cpp b/Sming/Arch/Host/Core/HardwarePWM.cpp
@@ -25,7 +25,7 @@
 
 #include <HardwarePWM.h>
 
-HardwarePWM::HardwarePWM(const uint8_t*, uint8_t no_of_pins) : channel_count(no_of_pins)
+HardwarePWM::HardwarePWM(const uint8_t* pins, uint8_t no_of_pins, bool usePhaseShift ) : channel_count(no_of_pins)
 {
 }
 

diff --git a/Sming/Arch/Rp2040/Core/HardwarePWM.cpp b/Sming/Arch/Rp2040/Core/HardwarePWM.cpp
@@ -31,7 +31,7 @@
 
 #define PWM_FREQ_DEFAULT 1000
 
-HardwarePWM::HardwarePWM(const uint8_t* pins, uint8_t noOfPins) : channel_count(noOfPins)
+HardwarePWM::HardwarePWM(const uint8_t* pins, uint8_t no_of_pins, bool usePhaseShift ) : channel_count(no_of_pins)
 {
 	assert(noOfPins > 0 && noOfPins <= PWM_CHANNEL_NUM_MAX);
 	noOfPins = std::min(uint8_t(PWM_CHANNEL_NUM_MAX), noOfPins);

diff --git a/Sming/Core/HardwarePWM.h b/Sming/Core/HardwarePWM.h
@@ -62,9 +62,16 @@ class HardwarePWM
 	/** @brief  Instantiate hardware PWM object
      *  @param  pins Pointer to array of pins to control
      *  @param  no_of_pins Quantity of elements in array of pins
+	 *  @param  usePhaseShift Use ledc's hpoint phase shift feature to stagger the rising edge of the PWM 
+	 * 						  singals evenly across the period. This is useful for driving multiple LEDs
+	 * 						  connected to the same power rail to reduce the peak current draw and help with 
+	 * 						  electromagnetic interference.
+	 *  @param  useSpreadSpectrum implement minimal spread spectrum modulation to further reduce EMI. This 
+	 * 						  feature uses a hardware timer to modulate the base frequency of the PWM signal.
+	 * 						  Depending on the base frequency, this may cause quite some system load, so 
+	 *                        choosing a good balance between CPU resources and acceptable EMI is important.
      */
-	HardwarePWM(const uint8_t* pins, uint8_t no_of_pins);
-
+	HardwarePWM(const uint8_t* pins, uint8_t no_of_pins, bool usePhaseShift=false);
 	virtual ~HardwarePWM();
 
 	/** @brief  Set PWM duty cycle
@@ -154,6 +161,8 @@ class HardwarePWM
 
 private:
 	uint8_t channel_count;
+	bool _usePhaseShift;
+	bool _useSpreadSpectrum;
 	uint8_t channels[PWM_CHANNEL_NUM_MAX];
 	uint32_t maxduty{0};
 };
-Original file line number
+Diff line change
@@ Expand Up / @@ -25,7 +25,7 @@ @@
     #include <HardwarePWM.h>
-    HardwarePWM::HardwarePWM(const uint8_t*, uint8_t no_of_pins) : channel_count(no_of_pins)
+    HardwarePWM::HardwarePWM(const uint8_t* pins, uint8_t no_of_pins, bool usePhaseShift ) : channel_count(no_of_pins)
     {
     }
@@ Expand Down @@