kopia lustrzana https://github.com/peterhinch/micropython-samples
DS3231 Support Pyboard D. Various updates and fixes.
Peter Hinch
rodzic
c259792a7c
commit
f62a6d8e1c
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@ -1,13 +1,14 @@
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# The DS3231 real time clock chip
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This is a remarkably inexpensive and easily interfaced battery-backed RTC. It
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is an ideal way to rapidly calibrate the Pyboard's RTC which can then achieve
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is an ideal way rapidly to calibrate the Pyboard's RTC which can then achieve
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similar levels of accuracy (+- ~2 mins/year). The chip can also provide
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accurate time to platforms lacking a good RTC (notably the ESP8266).
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Two drivers are provided:
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1. `ds3231_port.py` A multi-platform driver.
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2. `ds3231_pb.py` A Pyboard-specific driver with RTC calibration facility.
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2. `ds3231_pb.py` A Pyboard-specific driver with RTC calibration facility. For
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Pyboard 1.x and Pyboard D.
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Breakout boards are widely available. The interface is I2C. Pullups to 3.3V
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(typically 10KΩ) should be provided on the `SCL` and `SDA` lines if these are
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@ -15,7 +16,8 @@ not supplied on the breakout board.
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Both divers use edge detection to achieve millisecond-level precision from the
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DS3231. This enables relatively rapid accuracy testing of the platform's RTC,
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and fast calibration of the Pyboard's RTC.
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and fast calibration of the Pyboard's RTC. To quantify this, a sufficiently
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precise value of calibration may be acquired in 5-10 minutes.
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###### [Main README](../README.md)
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@ -23,10 +25,28 @@ and fast calibration of the Pyboard's RTC.
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This can use soft I2C so any pins may be used.
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It is based on the assumption that, where a hardware RTC exists, MicroPython's
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local time (`utime.localtime()`) is based on the RTC time. Changes to local
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time don't propagate to the RTC which must explicitly be set. This holds for
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the Pyboard, ESP8266 and ESP32.
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It uses the currently undocumented `RTC.datetime()` method to set and to query
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the platform RTC. This appears to be the only cross-platform way to do this.
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The meaning of the subseconds field is hardware dependent so this is ignored.
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The RTC is checked against the DS3231 by timing the transition of the seconds
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field of each clock (using system time to measure the relative timing of the
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edges).
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This example ran on a WeMos D1 Mini ESP8266 board, also a generic ESP32.
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```python
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from ds3231_port import DS3231
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from machine import Pin, I2C
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# Pins with pullups on ESP8266: clk=WeMos D3(P0) data=WeMos D4(P2)
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i2c = I2C(-1, Pin(0, Pin.OPEN_DRAIN), Pin(2, Pin.OPEN_DRAIN))
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ds3231 = DS3231(i2c)
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ds3231.get_time()
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```
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Testing the onboard RTC:
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```
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ds3231.rtc_test() # Takes 10 minutes
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```
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In my testing the ESP8266 RTC was out by 5%. The ESP32 was out by 6.7ppm or
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about 12 minutes/yr. Hardware samples will vary.
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## 1.1 The DS3231 class
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@ -34,35 +54,42 @@ Constructor:
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This takes one mandatory argument, an initialised I2C bus.
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Public methods:
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1. `get_time` Optional boolean arg `set_rtc=False`. If `set_rtc` is `True` it
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sets the platform's RTC from the DS3231. It returns the DS3231 time as a tuple
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in the same format as `utime.localtime()` except that yday (day of year) is 0.
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So the format is (year, month, day, hour, minute, second, wday, 0).
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1. `get_time(set_rtc=False)`. If `set_rtc` is `True` it sets the platform's
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RTC from the DS3231. It returns the DS3231 time as a tuple in the same format
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as `utime.localtime()` except that yday (day of year) is 0. So the format is
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(year, month, day, hour, minute, second, wday, 0).
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Note that on ports/platforms which don't support an RTC, if `set_rtc` is
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`True`, the local time will be set from the DS3231.
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2. `save_time` No args. Sets the DS3231 time from the platform's local time.
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3. `rtc_test` Optional args: `runtime=600`, `ppm=False`. This tests the
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platform's local time against the DS3231 returning the error in parts per
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million (if `ppm` is `True`) or seconds per year. A positive value indicates
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that the DS3231 clock leads the platform local time.
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2. `save_time()` No args. Sets the DS3231 time from the platform's local time.
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3. `rtc_test(runtime=600, ppm=False, verbose=True)`. This tests the platform's
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RTC time against the DS3231 returning the error in parts per million (if `ppm`
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is `True`) or seconds per year. A positive value indicates that the DS3231
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clock leads the platform RTC.
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The `runtime` value in seconds defines the duration of the test. The default
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of 10 minutes provides high accuracy but shorter durations will suffice on
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devices with poor RTC's (e.g. ESP8266).
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If `machine.RTC` is unsupported a `RuntimeError` will be thrown.
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# 2. The Pyboard driver
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The principal reason to use this driver is to calibrate the Pyboard's RTC. This
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does not yet support the Pyboard D.
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supports the Pyboard 1.x and Pyboard D. Note that the RTC on the Pyboard D is
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much more accurate than that on the Pyboard 1.x but can still be in error by up
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to 20ppm. It can benefit from calibration. For this to work reliably on the D a
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firmware build later than V1.12 is required: use a daily build if a later
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release is not yet available.
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This assumes that the DS3231 is connected to the hardware I2C port on the `X`
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or `Y` side of the board, and that the Pyboard's RTC is set to the correct time
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and date.
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The sample below assumes that the DS3231 is connected to the hardware I2C port
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via I2C(2) but any I2C may be used including soft I2C. Ensure that the Pyboard
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RTC is set to the correct time and date.
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Usage to calibrate the Pyboard's RTC. Takes 5 minutes.
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```python
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from ds3231_pb import DS3231
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ds3231 = DS3231('X')
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import machine
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i2c = machine.I2C(2) # Connected on 'Y' side Y9 clk Y10 data
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ds3231 = DS3231(i2c)
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ds3231.save_time() # Set DS3231 to match Pyboard RTC
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ds3231.calibrate()
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```
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@ -73,19 +100,19 @@ used the RTC will run accurately in the event of a power outage.
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## 2.1 The DS3231 class
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Constructor:
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This takes one mandatory argument, a string identifying the Pyboard side in use
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('X' or 'Y').
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This takes one mandatory argument, an I2C bus instantiated using the `machine`
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library.
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Public methods:
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1. `get_time` Optional boolean arg `set_rtc=False`. If `set_rtc` is True it
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sets the Pyboard's RTC from the DS3231. It returns the DS3231 time as a tuple
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in the same format as `utime.localtime()` except that yday (day of year) is 0.
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namely (year, month, day, hour, minute, second, wday, 0).
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2. `save_time` No args. Sets the DS3231 time from the Pyboard's RTC.
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3. `calibrate` Optional arg `minutes=5`. The time to run. This calculates the
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calibration factor and applies it to the Pyboard. It returns the calibration
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factor which may be stored in a file if the calibration needs to survive an
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outage of all power sources.
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1. `get_time(set_rtc=False)`. If `set_rtc` is `True` it sets the Pyboard's RTC
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from the DS3231. It returns the DS3231 time as a tuple in the same format as
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`utime.localtime()` except that yday (day of year) is 0.
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Namely (year, month, day, hour, minute, second, wday, 0).
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2. `save_time()` No args. Sets the DS3231 time from the Pyboard's RTC.
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3. `calibrate(minutes=5)`. The time to run. This calculates the calibration
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factor and applies it to the Pyboard. It returns the calibration factor which
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may be stored in a file if the calibration needs to survive an outage of all
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power sources.
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4. `getcal(minutes=5, cal=0, verbose=True)` Measures the performance of the
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Pyboard RTC against the DS3231. If `cal` is specified, the calibration factor
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is applied before the test is run. The default is to zero the calibration and
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@ -1,47 +1,36 @@
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# Pyboard driver for DS3231 precison real time clock.
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# Adapted from WiPy driver at https://github.com/scudderfish/uDS3231
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# Includes routine to calibrate the Pyboard's RTC from the DS3231
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# delta method now operates to 1mS precision
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# precison of calibration further improved by timing Pyboard RTC transition
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# Adapted by Peter Hinch, Jan 2016, Jan 2020 for Pyboard D
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# Pyboard D rtc.datetime()[7] counts microseconds. See end of page on
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# https://pybd.io/hw/pybd_sfxw.htm
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# Note docs for machine.RTC are wrong for Pyboard. The undocumented datetime
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# method seems to be the only way to set the RTC and it follows the same
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# convention as the pyb RTC's datetime method.
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import utime
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import pyb
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import machine
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import os
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d_series = os.uname().machine.split(' ')[0][:4] == 'PYBD'
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if d_series:
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pyb.Pin.board.EN_3V3.value(1)
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machine.Pin.board.EN_3V3.value(1)
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DS3231_I2C_ADDR = 104
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class DS3231Exception(OSError):
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pass
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rtc = pyb.RTC()
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rtc = machine.RTC()
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def now(): # Return the current time from the RTC in millisecs from year 2000
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secs = utime.time()
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if d_series:
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ms = rtc.datetime()[7] // 1000
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else:
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ms = 1000 * (255 -rtc.datetime()[7]) >> 8
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if ms < 50: # Might have just rolled over
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secs = utime.time()
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return 1000 * secs + ms
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def nownr(): # Return the current time from the RTC: caller ensures transition has occurred
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if d_series:
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return 1000 * utime.time() + rtc.datetime()[7] // 1000
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return 1000 * utime.time() + (1000 * (255 -rtc.datetime()[7]) >> 8)
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def get_ms(s): # Pyboard 1.x datetime to ms. Caller handles rollover.
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return (1000 * (255 - s[7]) >> 8) + s[6] * 1000 + s[5] * 60_000 + s[4] * 3_600_000
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def get_us(s): # For Pyboard D: convert datetime to μs. Caller handles rollover
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return (s[7] + s[6] * 1_000_000 + s[5] * 60_000_000 + s[4] * 3_600_000_000 )
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# Driver for DS3231 accurate RTC module (+- 1 min/yr) needs adapting for Pyboard
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# source https://github.com/scudderfish/uDS3231
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return s[7] + s[6] * 1_000_000 + s[5] * 60_000_000 + s[4] * 3_600_000_000
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def bcd2dec(bcd):
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return (((bcd & 0xf0) >> 4) * 10 + (bcd & 0x0f))
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@ -49,25 +38,25 @@ def dec2bcd(dec):
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tens, units = divmod(dec, 10)
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return (tens << 4) + units
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def tobytes(num):
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return num.to_bytes(1, 'little')
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class DS3231:
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def __init__(self, side = 'X'):
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side = side.lower()
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if side == 'x':
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bus = 1
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elif side == 'y':
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bus = 2
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else:
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raise ValueError('Side must be "X" or "Y"')
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self.ds3231 = pyb.I2C(bus, mode=pyb.I2C.MASTER, baudrate=400000)
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def __init__(self, i2c):
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self.ds3231 = i2c
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self.timebuf = bytearray(7)
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if DS3231_I2C_ADDR not in self.ds3231.scan():
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raise DS3231Exception("DS3231 not found on I2C bus at %d" % DS3231_I2C_ADDR)
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def get_time(self, set_rtc = False):
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def get_time(self, set_rtc=False):
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if set_rtc:
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data = self.await_transition() # For accuracy set RTC immediately after a seconds transition
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self.await_transition() # For accuracy set RTC immediately after a seconds transition
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else:
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data = self.ds3231.mem_read(self.timebuf, DS3231_I2C_ADDR, 0) # don't wait
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self.ds3231.readfrom_mem_into(DS3231_I2C_ADDR, 0, self.timebuf) # don't wait
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return self.convert(set_rtc)
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def convert(self, set_rtc=False):
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data = self.timebuf
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ss = bcd2dec(data[0])
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mm = bcd2dec(data[1])
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if data[2] & 0x40:
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return (YY, MM, DD, hh, mm, ss, wday -1, 0) # Time from DS3231 in time.time() format (less yday)
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def save_time(self):
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(YY, MM, DD, wday, hh, mm, ss, subsecs) = rtc.datetime()
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self.ds3231.mem_write(dec2bcd(ss), DS3231_I2C_ADDR, 0)
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self.ds3231.mem_write(dec2bcd(mm), DS3231_I2C_ADDR, 1)
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self.ds3231.mem_write(dec2bcd(hh), DS3231_I2C_ADDR, 2) # Sets to 24hr mode
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self.ds3231.mem_write(dec2bcd(wday), DS3231_I2C_ADDR, 3) # 1 == Monday, 7 == Sunday
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self.ds3231.mem_write(dec2bcd(DD), DS3231_I2C_ADDR, 4)
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(YY, MM, mday, hh, mm, ss, wday, yday) = utime.localtime() # Based on RTC
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self.ds3231.writeto_mem(DS3231_I2C_ADDR, 0, tobytes(dec2bcd(ss)))
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self.ds3231.writeto_mem(DS3231_I2C_ADDR, 1, tobytes(dec2bcd(mm)))
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self.ds3231.writeto_mem(DS3231_I2C_ADDR, 2, tobytes(dec2bcd(hh))) # Sets to 24hr mode
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self.ds3231.writeto_mem(DS3231_I2C_ADDR, 3, tobytes(dec2bcd(wday + 1))) # 1 == Monday, 7 == Sunday
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self.ds3231.writeto_mem(DS3231_I2C_ADDR, 4, tobytes(dec2bcd(mday))) # Day of month
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if YY >= 2000:
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self.ds3231.mem_write(dec2bcd(MM) | 0b10000000, DS3231_I2C_ADDR, 5)
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self.ds3231.mem_write(dec2bcd(YY-2000), DS3231_I2C_ADDR, 6)
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self.ds3231.writeto_mem(DS3231_I2C_ADDR, 5, tobytes(dec2bcd(MM) | 0b10000000)) # Century bit
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self.ds3231.writeto_mem(DS3231_I2C_ADDR, 6, tobytes(dec2bcd(YY-2000)))
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else:
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self.ds3231.mem_write(dec2bcd(MM), DS3231_I2C_ADDR, 5)
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self.ds3231.mem_write(dec2bcd(YY-1900), DS3231_I2C_ADDR, 6)
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def delta(self): # Return no. of mS RTC leads DS3231
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self.await_transition()
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rtc_ms = now()
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t_ds3231 = utime.mktime(self.get_time()) # To second precision, still in same sec as transition
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return rtc_ms - 1000 * t_ds3231
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self.ds3231.writeto_mem(DS3231_I2C_ADDR, 5, tobytes(dec2bcd(MM)))
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self.ds3231.writeto_mem(DS3231_I2C_ADDR, 6, tobytes(dec2bcd(YY-1900)))
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def await_transition(self): # Wait until DS3231 seconds value changes
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data = self.ds3231.mem_read(self.timebuf, DS3231_I2C_ADDR, 0)
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ss = data[0]
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while ss == data[0]:
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data = self.ds3231.mem_read(self.timebuf, DS3231_I2C_ADDR, 0)
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return data
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self.ds3231.readfrom_mem_into(DS3231_I2C_ADDR, 0, self.timebuf)
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ss = self.timebuf[0]
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while ss == self.timebuf[0]:
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self.ds3231.readfrom_mem_into(DS3231_I2C_ADDR, 0, self.timebuf)
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return self.timebuf
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# Get calibration factor for Pyboard RTC. Note that the DS3231 doesn't have millisecond resolution so we
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# wait for a seconds transition to emulate it.
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@ -134,24 +117,28 @@ class DS3231:
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rtc.calibration(cal) # Clear existing cal
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self.save_time() # Set DS3231 from RTC
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self.await_transition() # Wait for DS3231 to change: on a 1 second boundary
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tus = pyb.micros()
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tus = utime.ticks_us()
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st = rtc.datetime()[7]
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while rtc.datetime()[7] == st: # Wait for RTC to change
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pass
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t1 = pyb.elapsed_micros(tus) # t1 is duration (μs) between DS and RTC change (start)
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rtcstart = nownr() # RTC start time in mS
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dsstart = utime.mktime(self.get_time()) # DS start time in secs
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pyb.delay(minutes * 60000)
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t1 = utime.ticks_diff(utime.ticks_us(), tus) # t1 is duration (μs) between DS and RTC change (start)
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rtcstart = get_ms(rtc.datetime()) # RTC start time in mS
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dsstart = utime.mktime(self.convert()) # DS start time in secs as recorded by await_transition
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utime.sleep(minutes * 60)
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self.await_transition() # DS second boundary
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tus = pyb.micros()
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tus = utime.ticks_us()
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st = rtc.datetime()[7]
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while rtc.datetime()[7] == st:
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pass
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t2 = pyb.elapsed_micros(tus) # t2 is duration (μs) between DS and RTC change (end)
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rtcend = nownr()
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dsend = utime.mktime(self.get_time())
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t2 = utime.ticks_diff(utime.ticks_us(), tus) # t2 is duration (μs) between DS and RTC change (end)
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rtcend = get_ms(rtc.datetime())
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dsend = utime.mktime(self.convert())
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dsdelta = (dsend - dsstart) * 1000000 # Duration (μs) between DS edges as measured by DS3231
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rtcdelta = (rtcend - rtcstart) * 1000 + t1 -t2 # Duration (μs) between DS edges as measured by RTC and corrected
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if rtcend < rtcstart: # It's run past midnight. Assumption: run time < 1 day!
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rtcend += 24 * 3_600_000
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rtcdelta = (rtcend - rtcstart) * 1000 + t1 - t2 # Duration (μs) between DS edges as measured by RTC and corrected
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ppm = (1000000* (rtcdelta - dsdelta))/dsdelta
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if cal:
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verbose and print('Error {:4.1f}ppm {:4.1f}mins/year.'.format(ppm, ppm * 1.903))
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@ -169,13 +156,15 @@ class DS3231:
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t = rtc.datetime() # Get RTC time
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# Time of DS3231 transition measured by RTC in μs since start of day
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rtc_start_us = get_us(t)
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dsstart = utime.mktime(self.get_time()) # DS start time in secs
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pyb.delay(minutes * 60_000)
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dsstart = utime.mktime(self.convert()) # DS start time in secs
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utime.sleep(minutes * 60)
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self.await_transition() # Wait for DS second boundary
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t = rtc.datetime()
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# Time of DS3231 transition measured by RTC in μs since start of day
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rtc_end_us = get_us(t)
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dsend = utime.mktime(self.get_time()) # DS start time in secs
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dsend = utime.mktime(self.convert()) # DS end time in secs
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if rtc_end_us < rtc_start_us: # It's run past midnight. Assumption: run time < 1 day!
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rtc_end_us += 24 * 3_600_000_000
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||||
|
|
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|||
|
|
@ -96,13 +96,37 @@ class DS3231:
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|||
# one-seond boundaries and using ticks_ms() to time the RTC.
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||||
# For a 10 minute measurement +-1ms corresponds to 1.7ppm or 53s/yr. Longer
|
||||
# runtimes improve this, but the DS3231 is "only" good for +-2ppm over 0-40C.
|
||||
def rtc_test(self, runtime=600, ppm=False):
|
||||
factor = 1000000 if ppm else 31557600 # seconds per year
|
||||
self.await_transition() # Start on transition
|
||||
rtc_start = utime.ticks_ms() # and get RTC time NOW
|
||||
ds3231_start = utime.mktime(self.convert())
|
||||
def rtc_test(self, runtime=600, ppm=False, verbose=True):
|
||||
if rtc is None:
|
||||
raise RuntimeError('machine.RTC does not exist')
|
||||
verbose and print('Waiting {} minutes for result'.format(runtime//60))
|
||||
factor = 1_000_000 if ppm else 114_155_200 # seconds per year
|
||||
|
||||
self.await_transition() # Start on transition of DS3231. Record time in .timebuf
|
||||
t = utime.ticks_ms() # Get system time now
|
||||
ss = rtc.datetime()[6] # Seconds from system RTC
|
||||
while ss == rtc.datetime()[6]:
|
||||
pass
|
||||
ds = utime.ticks_diff(utime.ticks_ms(), t) # ms to transition of RTC
|
||||
ds3231_start = utime.mktime(self.convert()) # Time when transition occurred
|
||||
t = rtc.datetime()
|
||||
rtc_start = utime.mktime((t[0], t[1], t[2], t[4], t[5], t[6], t[3] - 1, 0)) # y m d h m s wday 0
|
||||
|
||||
utime.sleep(runtime) # Wait a while (precision doesn't matter)
|
||||
self.await_transition()
|
||||
d_rtc = utime.ticks_diff(utime.ticks_ms(), rtc_start)
|
||||
d_ds3231 = 1000 * (utime.mktime(self.convert()) - ds3231_start)
|
||||
return (d_ds3231 - d_rtc) * factor / d_ds3231
|
||||
|
||||
self.await_transition() # of DS3231 and record the time
|
||||
t = utime.ticks_ms() # and get system time now
|
||||
ss = rtc.datetime()[6] # Seconds from system RTC
|
||||
while ss == rtc.datetime()[6]:
|
||||
pass
|
||||
de = utime.ticks_diff(utime.ticks_ms(), t) # ms to transition of RTC
|
||||
ds3231_end = utime.mktime(self.convert()) # Time when transition occurred
|
||||
t = rtc.datetime()
|
||||
rtc_end = utime.mktime((t[0], t[1], t[2], t[4], t[5], t[6], t[3] - 1, 0)) # y m d h m s wday 0
|
||||
|
||||
d_rtc = 1000 * (rtc_end - rtc_start) + de - ds # ms recorded by RTC
|
||||
d_ds3231 = 1000 * (ds3231_end - ds3231_start) # ms recorded by DS3231
|
||||
ratio = (d_ds3231 - d_rtc) / d_ds3231
|
||||
ppm = ratio * 1_000_000
|
||||
verbose and print('DS3231 leads RTC by {:4.1f}ppm {:4.1f}mins/yr'.format(ppm, ppm*1.903))
|
||||
return ratio * factor
|
||||
|
|
|
|||
Ładowanie…
Reference in New Issue