RP2040_DS3231_SerialSync

Set the right time to a DS3231/DS1307 through serial port

This program works on a Waveshare pico zero board, but works as well over many others boards also if they aren't a RP2040 based one, (with the necessaries mods) and with the DS1307 too

The source code needs these two libraries:

• NeoPixelConnect Library by Alan Yorinks (https://github.com/MrYsLab/NeoPixelConnect)
• DS3231 Library by Wickert, A. D., Sandell, C. T., Schulz, B., & Ng, G. H. C. (https://github.com/NorthernWidget/DS3231)

and you can find both on ArduinoIDE Library Manager

It's an attempt to sync DS3231 time using only serial port and nothing else, there is a bash script accompaining this file who sends at second 00 the epoch of the PC to the pico serial port. Due to some lags from usb->pico->i2c->ds3231 registers, time will be not precise at 100%, rember that ds3231 doesn't allow to set ms or whatever, you only know that after writing the "seconds" register it start to use the new time.

Connection for RP2040 boards are:

  board  DS3231
  3v3    VCC  
  GND    GND  
  GPIO0  SDA
  GPIO1  SCL
  GPIO2  INT/SQW

hope you can find this code useful for some of your projects

For LINUX users:

set correct time with this command:

date +%s > /dev/ttyACM0

or better using the included bash script, that sends time through serial line of choice when precise "00" seconds occour:

  #!/bin/bash
  
  test=true
  
  while $test; do
          d=$(date +%S)
          if [ $d -eq 0 ]; then
                  #echo $(($(date +%s) +$1)) > /dev/ttyACM0
                  date +%s > /dev/ttyACM0
                  echo ">date sent to /dev/ttyACM0"
                  #date +%S.%N
                  sleep 1
                  test=false
          else
                  sleep 0.001
          fi
  done

Submitting the epoch trough the serial sets also the internal rp2040 rtc, when you reset the board the rtc gets losts, but not the DS3231, by pressing the "boot" button the rtc will be sets accordingly to the DS3231 time again.