6 files changed, 38 insertions, 11 deletions
diff --git a/ports/atmel-samd/background.c b/ports/atmel-samd/background.c
index 92648f42e..4cba7a110 100644
--- a/ports/atmel-samd/background.c
+++ b/ports/atmel-samd/background.c
@@ -26,11 +26,19 @@
 #include "background.h"
 
 #include "audio_dma.h"
+#include "tick.h"
 #include "usb.h"
 #include "usb_mass_storage.h"
 
+volatile uint64_t last_finished_tick = 0;
+
 void run_background_tasks(void) {
     audio_dma_background();
     usb_msc_background();
     usb_cdc_background();
+    last_finished_tick = ticks_ms;
+}
+
+bool background_tasks_ok(void) {
+    return ticks_ms - last_finished_tick < 1000;
 }
diff --git a/ports/atmel-samd/background.h b/ports/atmel-samd/background.h
index f7fb10a1f..e841049a4 100644
--- a/ports/atmel-samd/background.h
+++ b/ports/atmel-samd/background.h
@@ -27,6 +27,9 @@
 #ifndef MICROPY_INCLUDED_ATMEL_SAMD_BACKGROUND_H
 #define MICROPY_INCLUDED_ATMEL_SAMD_BACKGROUND_H
 
+#include <stdbool.h>
+
 void run_background_tasks(void);
+bool background_tasks_ok(void);
 
 #endif  // MICROPY_INCLUDED_ATMEL_SAMD_BACKGROUND_H
diff --git a/ports/atmel-samd/common-hal/microcontroller/__init__.c b/ports/atmel-samd/common-hal/microcontroller/__init__.c
index c57b6939c..ad4d81ddd 100644
--- a/ports/atmel-samd/common-hal/microcontroller/__init__.c
+++ b/ports/atmel-samd/common-hal/microcontroller/__init__.c
@@ -40,18 +40,10 @@ void common_hal_mcu_delay_us(uint32_t delay) {
     mp_hal_delay_us(delay);
 }
 
-// Interrupt flags that will be saved and restored during disable/Enable
-// interrupt functions below.
-
-// ASF4's interrupt disable doesn't handle duplicate calls
-volatile uint32_t interrupt_flags;
 volatile uint32_t nesting_count = 0;
 void common_hal_mcu_disable_interrupts(void) {
-    if (nesting_count == 0) {
-        interrupt_flags = __get_PRIMASK();
-        __disable_irq();
-        __DMB();
-    }
+    __disable_irq();
+    __DMB();
     nesting_count++;
 }
 
@@ -66,7 +58,7 @@ void common_hal_mcu_enable_interrupts(void) {
         return;
     }
     __DMB();
-    __set_PRIMASK(interrupt_flags);
+    __enable_irq();
 }
 
 extern uint32_t _ezero;
diff --git a/ports/atmel-samd/common-hal/pulseio/PulseIn.c b/ports/atmel-samd/common-hal/pulseio/PulseIn.c
index 99a60a829..dee32bbec 100644
--- a/ports/atmel-samd/common-hal/pulseio/PulseIn.c
+++ b/ports/atmel-samd/common-hal/pulseio/PulseIn.c
@@ -31,6 +31,7 @@
 #include "atmel_start_pins.h"
 #include "hal/include/hal_gpio.h"
 
+#include "background.h"
 #include "mpconfigport.h"
 #include "py/gc.h"
 #include "py/runtime.h"
@@ -60,10 +61,16 @@ void pulsein_interrupt_handler(uint8_t channel) {
     uint32_t current_us;
     uint64_t current_ms;
     current_tick(&current_ms, &current_us);
+
     // current_tick gives us the remaining us until the next tick but we want the number since the
     // last ms.
     current_us = 1000 - current_us;
     pulseio_pulsein_obj_t* self = get_eic_channel_data(channel);
+    if (!background_tasks_ok() || self->errored_too_fast) {
+        self->errored_too_fast = true;
+        common_hal_pulseio_pulsein_pause(self);
+        return;
+    }
     if (self->first_edge) {
         self->first_edge = false;
         pulsein_set_config(self, false);
@@ -118,6 +125,7 @@ void common_hal_pulseio_pulsein_construct(pulseio_pulsein_obj_t* self,
     self->first_edge = true;
     self->last_us = 0;
     self->last_ms = 0;
+    self->errored_too_fast = 0;
 
     set_eic_channel_data(pin->extint_channel, (void*) self);
 
@@ -157,6 +165,9 @@ void common_hal_pulseio_pulsein_resume(pulseio_pulsein_obj_t* self,
     // Make sure we're paused.
     common_hal_pulseio_pulsein_pause(self);
 
+    // Reset erroring
+    self->errored_too_fast = false;
+
     // Send the trigger pulse.
     if (trigger_duration > 0) {
         gpio_set_pin_pull_mode(self->pin, GPIO_PULL_OFF);
@@ -207,6 +218,11 @@ uint16_t common_hal_pulseio_pulsein_get_len(pulseio_pulsein_obj_t* self) {
     return self->len;
 }
 
+bool common_hal_pulseio_pulsein_get_paused(pulseio_pulsein_obj_t* self) {
+    uint32_t mask = 1 << self->channel;
+    return (EIC->INTENSET.reg & (mask << EIC_INTENSET_EXTINT_Pos)) == 0;
+}
+
 uint16_t common_hal_pulseio_pulsein_get_item(pulseio_pulsein_obj_t* self,
         int16_t index) {
     common_hal_mcu_disable_interrupts();
diff --git a/ports/atmel-samd/common-hal/pulseio/PulseIn.h b/ports/atmel-samd/common-hal/pulseio/PulseIn.h
index 3d79b50c3..f5326d9e5 100644
--- a/ports/atmel-samd/common-hal/pulseio/PulseIn.h
+++ b/ports/atmel-samd/common-hal/pulseio/PulseIn.h
@@ -43,6 +43,7 @@ typedef struct {
     volatile bool first_edge;
     volatile uint64_t last_ms;
     volatile uint16_t last_us;
+    volatile bool errored_too_fast;
 } pulseio_pulsein_obj_t;
 
 void pulsein_reset(void);
diff --git a/ports/atmel-samd/tick.c b/ports/atmel-samd/tick.c
index 6cd7c7833..81841c4af 100644
--- a/ports/atmel-samd/tick.c
+++ b/ports/atmel-samd/tick.c
@@ -60,6 +60,13 @@ void tick_init() {
     uint32_t ticks_per_ms = common_hal_mcu_processor_get_frequency() / 1000;
     SysTick_Config(ticks_per_ms-1);
     NVIC_EnableIRQ(SysTick_IRQn);
+    // Set all peripheral interrupt priorities to the lowest priority by default.
+    for (uint16_t i = 0; i < PERIPH_COUNT_IRQn; i++) {
+        NVIC_SetPriority(i, (1UL << __NVIC_PRIO_BITS) - 1UL);
+    }
+    // Bump up the systick interrupt.
+    NVIC_SetPriority(SysTick_IRQn, 1);
+    NVIC_SetPriority(USB_IRQn, 1);
 }
 
 void tick_delay(uint32_t us) {