nrf: add watchdog module

Add common-hal bindings to allow the watchdog module to be used
on nrf platforms.

Signed-off-by: Sean Cross <[email protected]>

Author: xobs

ports/nrf/common-hal/wdt/WDT.c

@@ -0,0 +1,40 @@
+#include "py/obj.h"
+#include "py/runtime.h"
+
+#include "shared-bindings/rtc/__init__.h"
+#include "nrf_wdt.h"
+
+#define WDT_RELOAD_COUNT 2
+
+void common_hal_wdt_init(uint32_t duration, bool pause_during_sleep) {
+    unsigned int channel;
+    nrf_wdt_behaviour_t behaviour = NRF_WDT_BEHAVIOUR_RUN_SLEEP_HALT;
+    if (pause_during_sleep) {
+        behaviour = NRF_WDT_BEHAVIOUR_PAUSE_SLEEP_HALT;
+    }
+
+    nrf_wdt_behaviour_set(NRF_WDT, behaviour);
+
+    uint64_t ticks = (duration * 32768ULL) / 1000;
+    if (ticks > UINT32_MAX) {
+        mp_raise_ValueError(translate("timeout duration exceeded the maximum supported value"));
+    }
+    nrf_wdt_reload_value_set(NRF_WDT, (uint32_t) ticks);
+
+    for (channel = 0; channel < WDT_RELOAD_COUNT; channel++) {
+        nrf_wdt_reload_request_enable(NRF_WDT, channel);
+    }
+
+    nrf_wdt_task_trigger(NRF_WDT, NRF_WDT_TASK_START);
+}
+
+void common_hal_wdt_feed(void) {
+    unsigned int channel;
+    for (channel = 0; channel < WDT_RELOAD_COUNT; channel++) {
+        nrf_wdt_reload_request_set(NRF_WDT, (nrf_wdt_rr_register_t)(NRF_WDT_RR0 + channel));
+    }
+}
+
+void common_hal_wdt_disable(void) {
+    // mp_raise_ValueError(translate("Watchdog timer cannot be disabled -- board will reset shortly"));
+}