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DS3231: Update docs.

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peterhinch 2023-02-17 13:16:10 +00:00
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DS3231/README.md
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@ -25,19 +25,17 @@ precise value of calibration may be acquired in 5-10 minutes.
This can use soft I2C so any pins may be used.
It uses the currently undocumented `RTC.datetime()` method to set and to query
the platform RTC. This appears to be the only cross-platform way to do this.
The meaning of the subseconds field is hardware dependent so this is ignored.
The RTC is checked against the DS3231 by timing the transition of the seconds
field of each clock (using system time to measure the relative timing of the
edges).
It uses the `RTC.datetime()` method to set and to query the platform RTC. The
meaning of the subseconds field is hardware dependent so this is ignored. The
RTC is checked against the DS3231 by timing the transition of the seconds field
of each clock (using system time to measure the relative timing of the edges).
This example ran on a WeMos D1 Mini ESP8266 board, also a generic ESP32.
```python
from ds3231_port import DS3231
from machine import Pin, I2C
from machine import Pin, SoftI2C
# Pins with pullups on ESP8266: clk=WeMos D3(P0) data=WeMos D4(P2)
i2c = I2C(-1, Pin(0, Pin.OPEN_DRAIN), Pin(2, Pin.OPEN_DRAIN))
i2c = SoftI2C(Pin(0, Pin.OPEN_DRAIN), Pin(2, Pin.OPEN_DRAIN))
ds3231 = DS3231(i2c)
ds3231.get_time()
```
@ -46,7 +44,8 @@ Testing the onboard RTC:
ds3231.rtc_test() # Takes 10 minutes
```
In my testing the ESP8266 RTC was out by 5%. The ESP32 was out by 6.7ppm or
about 12 minutes/yr. Hardware samples will vary.
about 12 minutes/yr. A PiPico was out by 1.7ppm, 3.2mins/yr. Hardware samples
will vary.
## 1.1 The DS3231 class