Add PNVRAM support to avoid forgetting the time during a reboot.

TODO.md

@@ -47,7 +47,7 @@ applications.
 ### Bootloader
 
  * [X] OTA bootloader update
- * [ ] RTC time measurement whilst in bootloader
+ * [X] RTC time measurement whilst in bootloader
 
 ### MicroPython
 

bootloader

@@ -1 +1 @@
-Subproject commit 7786926950902cf4ce49a93894f69a205d6fd325
+Subproject commit d8d7d76b17e188420f66705f0b319f6e80a328f2

micropython

@@ -1 +1 @@
-Subproject commit 5424de70d7cfb1d53828b54cd1df509c3f0fee74
+Subproject commit 8ea321106823866adcb6c4881b4045939b56cc3a

wasp/drivers/nrf_rtc.py

@@ -3,6 +3,7 @@
 
 """ Real Time Clock based on the nRF-family low power counter """
 
+import machine
 import time
 
 #class Stim(object):
@@ -20,6 +21,15 @@ class RTC(object):
 
     def __init__(self, counter):
         self.counter = counter
+
+	if machine.mem32[0x200039c0] == 0x1abe11ed and \
+	   machine.mem32[0x200039dc] == 0x10adab1e:
+            self.lastcount = self.counter.counter()
+	    self.offset = machine.mem32[0x200039c4]
+	    self._uptime = machine.mem32[0x200039c8] // 125
+	else:
+	    machine.mem32[0x200039c0] = 0x1abe11ed
+	    machine.mem32[0x200039dc] = 0x10adab1e
 	    self._uptime = 0
 	    self.set_localtime((2020, 3, 1, 3, 0, 0, 0, 0))
 
@@ -34,6 +44,7 @@ class RTC(object):
         self.lastcount += split
         self.lastcount &= (1 << 24) - 1   
         self._uptime += split
+        machine.mem32[0x200039c8] = self._uptime * 125
 
         return True
 
@@ -52,6 +63,7 @@ class RTC(object):
 
         lt = time.mktime(t)
         self.offset = lt - (self._uptime >> 3)
+        machine.mem32[0x200039c4] = self.offset
 
     def get_localtime(self):
         self.update()