enable NRFX RTC adafruit#1046

Author: nickzoic

ports/nrf/Makefile

@@ -140,6 +140,7 @@ SRC_NRFX = $(addprefix nrfx/,\
 	drivers/src/nrfx_twim.c \
 	drivers/src/nrfx_uarte.c \
 	drivers/src/nrfx_gpiote.c \
+	drivers/src/nrfx_rtc.c \
 	)
 
 ifdef EXTERNAL_FLASH_DEVICES

ports/nrf/common-hal/rtc/RTC.c

@@ -33,24 +33,44 @@
 #include "supervisor/shared/translate.h"
 
 #include "nrfx_rtc.h"
+#include "nrf_clock.h"
 
-static uint32_t _rtc_seconds = 0;
+#define RTC_CLOCK_HZ (8)
 
-void rtc_handler(nrfx_rtc_int_type_t int_type) {
+static uint32_t rtc_offset = 0;
+
+const nrfx_rtc_t rtc_instance = NRFX_RTC_INSTANCE(0);
 
+const nrfx_rtc_config_t rtc_config = {
+	.prescaler = RTC_FREQ_TO_PRESCALER(RTC_CLOCK_HZ),
+	.reliable = 0,
+	.tick_latency = 0,
+	.interrupt_priority = 6
+};
+
+void rtc_handler(nrfx_rtc_int_type_t int_type) {
+    // do nothing
 }
 
 void rtc_init(void) {
+    if (!nrf_clock_lf_is_running()) {
+        nrf_clock_task_trigger(NRF_CLOCK_TASK_LFCLKSTART);
+    }
+    nrfx_rtc_counter_clear(&rtc_instance);
+    nrfx_rtc_init(&rtc_instance, &rtc_config, rtc_handler);
+    nrfx_rtc_enable(&rtc_instance);
 }
 
 void common_hal_rtc_get_time(timeutils_struct_time_t *tm) {
-    timeutils_seconds_since_2000_to_struct_time(_rtc_seconds, tm);
+    uint32_t t = rtc_offset + (nrfx_rtc_counter_get(&rtc_instance) / RTC_CLOCK_HZ );
+    timeutils_seconds_since_2000_to_struct_time(t, tm);
 }
 
 void common_hal_rtc_set_time(timeutils_struct_time_t *tm) {
-    _rtc_seconds = timeutils_seconds_since_2000(
+    rtc_offset = timeutils_seconds_since_2000(
         tm->tm_year, tm->tm_mon, tm->tm_mday, tm->tm_hour, tm->tm_min, tm->tm_sec
     );
+    nrfx_rtc_counter_clear(&rtc_instance);
 }
 
 // A positive value speeds up the clock by removing clock cycles.

ports/nrf/nrfx_config.h

@@ -70,6 +70,9 @@
 #define NRFX_PWM3_ENABLED 0
 #endif
 
+#define NRFX_RTC_ENABLED 1
+#define NRFX_RTC0_ENABLED 1
+
 // TIMERS
 #define NRFX_TIMER_ENABLED 1
 // Don't enable TIMER0: it's used by the SoftDevice.

shared-bindings/rtc/RTC.c

@@ -36,6 +36,7 @@
 #include "shared-bindings/time/__init__.h"
 #include "supervisor/shared/translate.h"
 
+/*
 void MP_WEAK common_hal_rtc_get_time(timeutils_struct_time_t *tm) {
     mp_raise_NotImplementedError(translate("RTC is not supported on this board"));
 }
@@ -51,6 +52,7 @@ int MP_WEAK common_hal_rtc_get_calibration(void) {
 void MP_WEAK common_hal_rtc_set_calibration(int calibration) {
     mp_raise_NotImplementedError(translate("RTC calibration is not supported on this board"));
 }
+*/
 
 const rtc_rtc_obj_t rtc_rtc_obj = {{&rtc_rtc_type}};