Hello,
I'm using a PCF8523 based RTC board and it's gaining over 12 seconds per 24 hours. I'd like to track the variance while it's connected via serial cable to my computer. This would allow me to figure out the best offset for calibrating. I thought it would be simple to record the local time, from the RTC, and also the time from the connected computer and write both to an SD card. But I can't find any way to get the computer time into the arduino dynamically. Thoughts?
Did you follow these instructions? "This product does not come with a CR1220 coin cell battery. We recommend you purchase a coin cell battery to use with this product."
Paul
That coin cell is just to keep the time between power cycles, and has nothing to do with the inaccuracy of the product.
OP: to get the time from your computer you have to get (write?) some software that prints the time to the USB port on regular intervals, then have the Arduino read this information. E.g. by setting up a cron job, running every hour, calling a short bash script that sends the current time over the USB port.
The sure in your link says ...”The PCF8523 is simple and inexpensive but not a high precision device. It may lose or gain a second or two per day. For a high-precision, temperature compensated alternative, please check out the DS3231 precision RTC.”
Just buy the 3231 - they are very cheap and very accurate - see eBay .
The problem with what you propose is that the drift is probably temperature dependant , so you won’t get the accuracy.