Clear the pending IRQ in the NVIC as well.

ports/nrf/common-hal/audiobusio/I2SOut.c

@@ -322,6 +322,7 @@ bool common_hal_audiobusio_i2sout_get_playing(audiobusio_i2sout_obj_t* self) {
 void i2s_background(void) {
     if (NVIC_GetPendingIRQ(I2S_IRQn) && NRF_I2S->EVENTS_TXPTRUPD) {
         NRF_I2S->EVENTS_TXPTRUPD = 0;
+        NVIC_ClearPendingIRQ(I2S_IRQn);
         if (instance) {
             i2s_buffer_fill(instance);
         } else {

ports/nrf/common-hal/audiopwmio/PWMAudioOut.c

@@ -88,7 +88,6 @@ void audiopwmout_reset() {
 }
 
 STATIC void fill_buffers(audiopwmio_pwmaudioout_obj_t *self, int buf) {
-    self->pwm->EVENTS_SEQSTARTED[1-buf] = 0;
     uint16_t *dev_buffer = self->buffers[buf];
     uint8_t *buffer;
     uint32_t buffer_length;
@@ -145,8 +144,15 @@ STATIC void audiopwmout_background_obj(audiopwmio_pwmaudioout_obj_t *self) {
         if (stopped)
             self->pwm->TASKS_STOP = 1;
     } else if (!self->paused && !self->single_buffer) {
-        if (self->pwm->EVENTS_SEQSTARTED[0]) fill_buffers(self, 1);
+        if (self->pwm->EVENTS_SEQSTARTED[0]) {
-        if (self->pwm->EVENTS_SEQSTARTED[1]) fill_buffers(self, 0);
+            fill_buffers(self, 1);
+            self->pwm->EVENTS_SEQSTARTED[0] = 0;
+        }
+        if (self->pwm->EVENTS_SEQSTARTED[1]) {
+            fill_buffers(self, 0);
+            self->pwm->EVENTS_SEQSTARTED[1] = 0;
+        }
+        NVIC_ClearPendingIRQ(self->pwm_irq);
     }
 }
 
@@ -168,7 +174,8 @@ void audiopwmout_background() {
 // Caller validates that pins are free.
 void common_hal_audiopwmio_pwmaudioout_construct(audiopwmio_pwmaudioout_obj_t* self,
         const mcu_pin_obj_t* left_channel, const mcu_pin_obj_t* right_channel, uint16_t quiescent_value) {
-    self->pwm = pwmout_allocate(256, PWM_PRESCALER_PRESCALER_DIV_1, true, NULL, NULL);
+    self->pwm = pwmout_allocate(256, PWM_PRESCALER_PRESCALER_DIV_1, true, NULL, NULL,
+                                &self->pwm_irq);
     if (!self->pwm) {
         mp_raise_RuntimeError(translate("All timers in use"));
     }

ports/nrf/common-hal/audiopwmio/PWMAudioOut.h

@@ -44,6 +44,8 @@ typedef struct {
     uint8_t sample_channel_count;
     uint8_t bytes_per_sample;
 
+    IRQn_Type pwm_irq;
+
     bool playing;
     bool stopping;
     bool paused;

ports/nrf/common-hal/pulseio/PWMOut.c

@@ -139,11 +139,15 @@ bool convert_frequency(uint32_t frequency, uint16_t *countertop, nrf_pwm_clk_t *
     return false;
 }
 
+// We store these in an array because we cannot compute them.
+static IRQn_Type pwm_irqs[4] = {PWM0_IRQn, PWM1_IRQn, PWM2_IRQn, PWM3_IRQn};
+
 NRF_PWM_Type *pwmout_allocate(uint16_t countertop, nrf_pwm_clk_t base_clock,
-        bool variable_frequency, int8_t *channel_out, bool *pwm_already_in_use_out) {
+        bool variable_frequency, int8_t *channel_out, bool *pwm_already_in_use_out,
+        IRQn_Type* irq) {
     for (size_t pwm_index = 0; pwm_index < MP_ARRAY_SIZE(pwms); pwm_index++) {
         NRF_PWM_Type *pwm = pwms[pwm_index];
-        bool pwm_already_in_use = pwm->ENABLE & SPIM_ENABLE_ENABLE_Msk;
+        bool pwm_already_in_use = pwm->ENABLE & PWM_ENABLE_ENABLE_Msk;
         if (pwm_already_in_use) {
             if (variable_frequency) {
                 // Variable frequency requires exclusive use of a PWM, so try the next one.
@@ -156,20 +160,30 @@ NRF_PWM_Type *pwmout_allocate(uint16_t countertop, nrf_pwm_clk_t base_clock,
                 for (size_t chan = 0; chan < CHANNELS_PER_PWM; chan++) {
                     if (pwm->PSEL.OUT[chan] == 0xFFFFFFFF) {
                         // Channel is free.
-                        if(channel_out)
+                        if (channel_out) {
                             *channel_out = chan;
-                        if(pwm_already_in_use_out)
+                        }
+                        if (pwm_already_in_use_out) {
                             *pwm_already_in_use_out = pwm_already_in_use;
+                        }
+                        if (irq) {
+                            *irq = pwm_irqs[pwm_index];
+                        }
                         return pwm;
                     }
                 }
             }
         } else {
             // PWM not yet in use, so we can start to use it. Use channel 0.
-            if(channel_out)
+            if (channel_out) {
                 *channel_out = 0;
-            if(pwm_already_in_use_out)
+            }
+            if (pwm_already_in_use_out) {
                 *pwm_already_in_use_out = pwm_already_in_use;
+            }
+            if (irq) {
+                *irq = pwm_irqs[pwm_index];
+            }
             return pwm;
         }
     }
@@ -208,7 +222,7 @@ pwmout_result_t common_hal_pulseio_pwmout_construct(pulseio_pwmout_obj_t* self,
     int8_t channel;
     bool pwm_already_in_use;
     self->pwm = pwmout_allocate(countertop, base_clock, variable_frequency,
-        &channel, &pwm_already_in_use);
+        &channel, &pwm_already_in_use, NULL);
 
     if (self->pwm == NULL) {
         return PWMOUT_ALL_TIMERS_IN_USE;

ports/nrf/common-hal/pulseio/PWMOut.h

@@ -42,7 +42,8 @@ typedef struct {
 
 void pwmout_reset(void);
 NRF_PWM_Type *pwmout_allocate(uint16_t countertop, nrf_pwm_clk_t base_clock,
-    bool variable_frequency, int8_t *channel_out, bool *pwm_already_in_use_out);
+    bool variable_frequency, int8_t *channel_out, bool *pwm_already_in_use_out,
+    IRQn_Type *irq);
 void pwmout_free_channel(NRF_PWM_Type *pwm, int8_t channel);
 
 #endif // MICROPY_INCLUDED_NRF_COMMON_HAL_PULSEIO_PWMOUT_H