extmod/ntptime: Factor out ntptime module from esp8266 port.

The ntptime module was previously only included in the ESP8266 port.  This
commit factors that module out into the extmod directory, makes it support
different epochs, and includes it in the rp2 port.

extmod/ntptime.py

@@ -1,3 +1,5 @@
+import utime
+
 try:
     import usocket as socket
 except:
@@ -7,9 +9,6 @@ try:
 except:
     import struct
 
-# (date(2000, 1, 1) - date(1900, 1, 1)).days * 24*60*60
-NTP_DELTA = 3155673600
-
 # The NTP host can be configured at runtime by doing: ntptime.host = 'myhost.org'
 host = "pool.ntp.org"
 
@@ -26,6 +25,17 @@ def time():
     finally:
         s.close()
     val = struct.unpack("!I", msg[40:44])[0]
+
+    EPOCH_YEAR = utime.gmtime(0)[0]
+    if EPOCH_YEAR == 2000:
+        # (date(2000, 1, 1) - date(1900, 1, 1)).days * 24*60*60
+        NTP_DELTA = 3155673600
+    elif EPOCH_YEAR == 1970:
+        # (date(1970, 1, 1) - date(1900, 1, 1)).days * 24*60*60
+        NTP_DELTA = 2208988800
+    else:
+        raise Exception("Unsupported epoch: {}".format(EPOCH_YEAR))
+
     return val - NTP_DELTA
 
 
@@ -33,7 +43,6 @@ def time():
 def settime():
     t = time()
     import machine
-    import utime
 
     tm = utime.gmtime(t)
     machine.RTC().datetime((tm[0], tm[1], tm[2], tm[6] + 1, tm[3], tm[4], tm[5], 0))

ports/esp32/boards/manifest.py

@@ -1,6 +1,6 @@
 freeze("$(PORT_DIR)/modules")
 freeze("$(MPY_DIR)/tools", ("upip.py", "upip_utarfile.py"))
-freeze("$(MPY_DIR)/ports/esp8266/modules", "ntptime.py")
+freeze("$(MPY_DIR)/extmod", "ntptime.py")
 freeze("$(MPY_DIR)/drivers/dht", "dht.py")
 freeze("$(MPY_DIR)/drivers/onewire")
 include("$(MPY_DIR)/extmod/uasyncio/manifest.py")

ports/esp8266/boards/GENERIC_512K/manifest.py

@@ -1,5 +1,4 @@
 freeze("$(BOARD_DIR)", "_boot.py", opt=3)
-freeze("$(PORT_DIR)/modules", ("apa102.py", "ntptime.py", "port_diag.py"))
 freeze("$(MPY_DIR)/drivers/dht", "dht.py")
 freeze("$(MPY_DIR)/drivers/onewire")
 include("$(MPY_DIR)/extmod/webrepl/manifest.py")

ports/esp8266/boards/manifest.py

@@ -1,4 +1,5 @@
 freeze("$(PORT_DIR)/modules")
+freeze("$(MPY_DIR)/extmod", "ntptime.py")
 freeze("$(MPY_DIR)/tools", ("upip.py", "upip_utarfile.py"))
 freeze("$(MPY_DIR)/drivers/dht", "dht.py")
 freeze("$(MPY_DIR)/drivers/onewire")

ports/rp2/boards/PICO_W/manifest.py

@@ -2,6 +2,7 @@ include("../manifest.py")
 
 freeze("$(MPY_DIR)/tools", "upip.py")
 freeze("$(MPY_DIR)/tools", "upip_utarfile.py")
+freeze("$(MPY_DIR)/extmod", "ntptime.py")
 
 if os.path.isdir(convert_path("$(MPY_LIB_DIR)")):
     freeze("$(MPY_LIB_DIR)/python-ecosys/urequests", "urequests.py")