add rollover blocking to analogWrite

this ensures that (when the timer is running) at least one pulse is emitted at each desired setting

this removes concerns about calling analogWrite too often and changing the duty cycle

the tradeoff is that analogWrite is now a blocking function that could take up to one whole timer period

Author: oclyke

cores/arduino/ard_sup/analog/ap3_analog.cpp

@@ -506,6 +506,19 @@ ap3_err_t ap3_pwm_output(uint8_t pin, uint32_t th, uint32_t fw, uint32_t clk)
                                 output,
                                 AM_HAL_GPIO_PIN_DRIVESTRENGTH_12MA); //
 
+    // if timer is running wait for timer value to roll over (will indicate that at least one pulse has been emitted)
+    AM_CRITICAL_BEGIN // critical section when reading / writing config registers
+    if(*((uint32_t*)CTIMERADDRn(CTIMER, timer, CTRL0)) & (CTIMER_CTRL0_TMRA0EN_Msk | CTIMER_CTRL0_TMRB0EN_Msk)){
+        uint32_t current = 0;
+        uint32_t last = 0;
+        do {
+            last = current;
+            current = am_hal_ctimer_read( timer, segment);
+        }while(current >= last);
+    }
+
+    AM_CRITICAL_END // end critical section
+
     // clear timer (also stops the timer)
     am_hal_ctimer_clear(timer, segment);