Setting DS3231 programmatically

[PhilTIlson]

I have a problem with setting a DS3231 RTC clock from within the program.

I am using the ds3231_i2c library and everything is working fine within the program. Initially I set the clock to the correct time using the recommended code, which is used once then commented out:

current_time = b'\x30\x52\x12\x03\x03\x11\x22' # sec min hour week day mon year
time.sleep(0.1)
ds.set_time(current_time)

Again, this works fine.

However, there may be a situation when the RTC loses the correct time and the user needs to reset it within the program. My problem is trying to recreate the current_time = b'\x30\x52\x12\x03\x03\x11\x22' line. I'm not very familiar with byte strings and whatever I try to do to create this line fails! The backslashes seem to be interpreted as escape characters when I try to build the string.

I can easily obtain the necessary settings in the form ['22', '11', '7', '17', '3', '0'] but how do I then convert this into the required form?

I've been struggling over this for a day without success, so I'd be grateful for any advice.

[davefes]

Maybe, look at ubinascii

[scruss]

Is it this library you're using? balance19/micropython_DS3231: A library to run the DS3231 RTC on Raspberry Pi Pico

That's a really odd way to go about setting the clock. Looks like the library is expecting binary coded decimal.

A couple of routines like this might help:

def bcd(n):
    n = n % 100
    return 16 * (n // 10) + n % 10

def date_to_bytes(sec, minutes, hour, week, day, month, year):
    # week is week of the year, seemingly
    return bytes(
        [bcd(sec), bcd(minutes), bcd(hour), bcd(week),
         bcd(day), bcd(month), bcd(year)]
    )

# example 2022-11-07 21:25:00 (in week 45)
print(date_to_bytes(0, 25, 21, 45, 7, 11, 22))

This returns b'\x00%!E\x07\x11"', which is a slightly more compact way of saying the expected b'\x00\x25\x21\x45\x07\x11\x22'.

Alternatively, you could use a different library. Peter Hinch's ds3231_port.py works well for me, with library docs here: The DS3231 real time clock chip

[PhilTIlson]

Many thanks for both prompt replies. scruss - that works perfectly! Thank you.

[peterhinch]

See also this module.

[scruss]

I mentioned that one, Peter. It's the one I use.

[peterhinch]

Oops! So you did.