extend RP2040 PWM to support low speeds

Author: runger1101001

src/drivers/hardware_specific/rp2040/rp2040_mcu.cpp

@@ -30,11 +30,12 @@ void setupPWM(int pin, long pwm_frequency, bool invert, RP2040DriverParams* para
 	params->pins[index] = pin;
 	params->slice[index] = slice;
 	params->chan[index] = chan;
-	pwm_set_clkdiv_int_frac(slice, 1, 0); // fastest pwm we can get
-	pwm_set_phase_correct(slice, true);
-	uint16_t wrapvalue = ((125L * 1000L * 1000L) / pwm_frequency) / 2L - 1L;
-	if (wrapvalue < 999) wrapvalue = 999; // 66kHz, resolution 1000
-	if (wrapvalue > 12499) wrapvalue = 12499; // 20kHz, resolution 12500
+	uint32_t sysclock_hz = machine.freq();
+	uint32_t factor = 4096 * 2 * pwm_frequency;
+	uint32_t div = sysclock_hz / factor;
+	if (sysclock_hz % factor !=0) div+=1;
+	if (div < 16) div = 16;
+	uint32_t wrapvalue = sysclock_hz *16 / div / pwm_frequency - 1;
 #ifdef SIMPLEFOC_DEBUG_RP2040
 	SimpleFOCDebug::print("Configuring pin ");
 	SimpleFOCDebug::print(pin);
@@ -44,9 +45,17 @@ void setupPWM(int pin, long pwm_frequency, bool invert, RP2040DriverParams* para
 	SimpleFOCDebug::print((int)chan);
 	SimpleFOCDebug::print(" frequency ");
 	SimpleFOCDebug::print((int)pwm_frequency);
+	SimpleFOCDebug::print(" divisor ");
+	SimpleFOCDebug::print((int)(div>>4));
+	SimpleFOCDebug::print(".");
+	SimpleFOCDebug::print((int)(div&0xF));
 	SimpleFOCDebug::print(" top value ");
 	SimpleFOCDebug::println(wrapvalue);
 #endif
+	if (wrapvalue < 999)
+		SimpleFOCDebug::println("Warning: PWM resolution is low.");
+	pwm_set_clkdiv_int_frac(slice, div>>4, div&0xF);
+	pwm_set_phase_correct(slice, true);
 	pwm_set_wrap(slice, wrapvalue);
 	wrapvalues[slice] = wrapvalue;
 	if (invert) {

src/drivers/hardware_specific/rp2040/rp2040_mcu.h

@@ -2,6 +2,8 @@
 
 #pragma once
 
+#include "Arduino.h"
+
 #if defined(TARGET_RP2040)