kopia lustrzana https://github.com/peterhinch/micropython-samples
144 wiersze
6.1 KiB
Python
144 wiersze
6.1 KiB
Python
# Pyboard driver for DS3231 precison real time clock.
|
|
# Adapted from WiPy driver at https://github.com/scudderfish/uDS3231
|
|
# Includes routine to calibrate the Pyboard's RTC from the DS3231
|
|
# delta method now operates to 1mS precision
|
|
# precison of calibration further improved by timing Pyboard RTC transition
|
|
# Adapted by Peter Hinch, Jan 2016
|
|
|
|
import utime, pyb
|
|
DS3231_I2C_ADDR = 104
|
|
|
|
class DS3231Exception(OSError):
|
|
pass
|
|
|
|
rtc = pyb.RTC()
|
|
|
|
def now(): # Return the current time from the RTC in millisecs from year 2000
|
|
secs = utime.time()
|
|
ms = 1000 * (255 -rtc.datetime()[7]) >> 8
|
|
if ms < 50: # Might have just rolled over
|
|
secs = utime.time()
|
|
return 1000 * secs + ms
|
|
|
|
def nownr(): # Return the current time from the RTC: caller ensures transition has occurred
|
|
return 1000 * utime.time() + (1000 * (255 -rtc.datetime()[7]) >> 8)
|
|
|
|
# Driver for DS3231 accurate RTC module (+- 1 min/yr) needs adapting for Pyboard
|
|
# source https://github.com/scudderfish/uDS3231
|
|
def bcd2dec(bcd):
|
|
return (((bcd & 0xf0) >> 4) * 10 + (bcd & 0x0f))
|
|
|
|
def dec2bcd(dec):
|
|
tens, units = divmod(dec, 10)
|
|
return (tens << 4) + units
|
|
|
|
class DS3231:
|
|
def __init__(self, side = 'X'):
|
|
side = side.lower()
|
|
if side == 'x':
|
|
bus = 1
|
|
elif side == 'y':
|
|
bus = 2
|
|
else:
|
|
raise ValueError('Side must be "X" or "Y"')
|
|
self.ds3231 = pyb.I2C(bus, mode=pyb.I2C.MASTER, baudrate=400000)
|
|
self.timebuf = bytearray(7)
|
|
if DS3231_I2C_ADDR not in self.ds3231.scan():
|
|
raise DS3231Exception("DS3231 not found on I2C bus at %d" % DS3231_I2C_ADDR)
|
|
|
|
def get_time(self, set_rtc = False):
|
|
if set_rtc:
|
|
data = self.await_transition() # For accuracy set RTC immediately after a seconds transition
|
|
else:
|
|
data = self.ds3231.mem_read(self.timebuf, DS3231_I2C_ADDR, 0) # don't wait
|
|
ss = bcd2dec(data[0])
|
|
mm = bcd2dec(data[1])
|
|
if data[2] & 0x40:
|
|
hh = bcd2dec(data[2] & 0x1f)
|
|
if data[2] & 0x20:
|
|
hh += 12
|
|
else:
|
|
hh = bcd2dec(data[2])
|
|
wday = data[3]
|
|
DD = bcd2dec(data[4])
|
|
MM = bcd2dec(data[5] & 0x1f)
|
|
YY = bcd2dec(data[6])
|
|
if data[5] & 0x80:
|
|
YY += 2000
|
|
else:
|
|
YY += 1900
|
|
if set_rtc:
|
|
rtc.datetime((YY, MM, DD, wday, hh, mm, ss, 0))
|
|
return (YY, MM, DD, hh, mm, ss, wday -1, 0) # Time from DS3231 in time.time() format (less yday)
|
|
|
|
def save_time(self):
|
|
(YY, MM, DD, wday, hh, mm, ss, subsecs) = rtc.datetime()
|
|
self.ds3231.mem_write(dec2bcd(ss), DS3231_I2C_ADDR, 0)
|
|
self.ds3231.mem_write(dec2bcd(mm), DS3231_I2C_ADDR, 1)
|
|
self.ds3231.mem_write(dec2bcd(hh), DS3231_I2C_ADDR, 2) # Sets to 24hr mode
|
|
self.ds3231.mem_write(dec2bcd(wday), DS3231_I2C_ADDR, 3) # 1 == Monday, 7 == Sunday
|
|
self.ds3231.mem_write(dec2bcd(DD), DS3231_I2C_ADDR, 4)
|
|
if YY >= 2000:
|
|
self.ds3231.mem_write(dec2bcd(MM) | 0b10000000, DS3231_I2C_ADDR, 5)
|
|
self.ds3231.mem_write(dec2bcd(YY-2000), DS3231_I2C_ADDR, 6)
|
|
else:
|
|
self.ds3231.mem_write(dec2bcd(MM), DS3231_I2C_ADDR, 5)
|
|
self.ds3231.mem_write(dec2bcd(YY-1900), DS3231_I2C_ADDR, 6)
|
|
|
|
def delta(self): # Return no. of mS RTC leads DS3231
|
|
self.await_transition()
|
|
rtc_ms = now()
|
|
t_ds3231 = utime.mktime(self.get_time()) # To second precision, still in same sec as transition
|
|
return rtc_ms - 1000 * t_ds3231
|
|
|
|
def await_transition(self): # Wait until DS3231 seconds value changes
|
|
data = self.ds3231.mem_read(self.timebuf, DS3231_I2C_ADDR, 0)
|
|
ss = data[0]
|
|
while ss == data[0]:
|
|
data = self.ds3231.mem_read(self.timebuf, DS3231_I2C_ADDR, 0)
|
|
return data
|
|
|
|
# Get calibration factor for Pyboard RTC. Note that the DS3231 doesn't have millisecond resolution so we
|
|
# wait for a seconds transition to emulate it.
|
|
# This function returns the required calibration factor for the RTC (approximately the no. of ppm the
|
|
# RTC lags the DS3231).
|
|
# Delay(min) Outcome (successive runs). Note 1min/yr ~= 2ppm
|
|
# 5 173 169 173 173 173
|
|
# 10 171 173 171
|
|
# 20 172 172 174
|
|
# 40 173 172 173 Mean: 172.3
|
|
# Note calibration factor is not saved on power down unless an RTC backup battery is used. An option is
|
|
# to store the calibration factor on disk and issue rtc.calibration(factor) on boot.
|
|
|
|
def getcal(self, minutes=5):
|
|
rtc.calibration(0) # Clear existing cal
|
|
self.save_time() # Set DS3231 from RTC
|
|
self.await_transition() # Wait for DS3231 to change: on a 1 second boundary
|
|
tus = pyb.micros()
|
|
st = rtc.datetime()[7]
|
|
while rtc.datetime()[7] == st: # Wait for RTC to change
|
|
pass
|
|
t1 = pyb.elapsed_micros(tus) # t1 is duration (uS) between DS and RTC change (start)
|
|
rtcstart = nownr() # RTC start time in mS
|
|
dsstart = utime.mktime(self.get_time()) # DS start time in secs
|
|
pyb.delay(minutes * 60000)
|
|
self.await_transition() # DS second boundary
|
|
tus = pyb.micros()
|
|
st = rtc.datetime()[7]
|
|
while rtc.datetime()[7] == st:
|
|
pass
|
|
t2 = pyb.elapsed_micros(tus) # t2 is duration (uS) between DS and RTC change (end)
|
|
rtcend = nownr()
|
|
dsend = utime.mktime(self.get_time())
|
|
dsdelta = (dsend - dsstart) * 1000000 # Duration (uS) between DS edges as measured by DS3231
|
|
rtcdelta = (rtcend - rtcstart) * 1000 + t1 -t2 # Duration (uS) between DS edges as measured by RTC and corrected
|
|
ppm = (1000000* (rtcdelta - dsdelta))/dsdelta
|
|
return int(-ppm/0.954)
|
|
|
|
def calibrate(self, minutes=5):
|
|
print('Waiting {} minutes to acquire calibration factor...'.format(minutes))
|
|
cal = self.getcal(minutes)
|
|
rtc.calibration(cal)
|
|
print('Pyboard RTC is calibrated. Factor is {}.'.format(cal))
|
|
return cal
|