[IARC] Groundhog Day #244

Barry Hansen

Thanks Rod. I drilled into this Griduino quirk and improved the work loop timing. Now the GMT clock is updated within a fraction of a second from WWV. You can download the latest v0.25 binary from GitHub (

My old mindset of “cpu cycles are precious, don’t waste’m” is only slowly adjusting to today’s world of dedicated hardware. Hey, this Arduino has nothing else to do, so why not update everything 10-20 times a second even though the real-world clock’s second hand ticks along more slowly. After all, the Cortex M4 cpu runs at 120 MHz and it’s idle most of the time.

Happy Groundhog Day #245,

Barry Hansen K7BWH

PS – Your cellphone’s second hand is probably slightly more accurate than this display.

PPS – Usability studies at IBM found that visual delays of 75 msec or less are indistinguishable from 0 msec.

PPPS – In Griduino hardware, the time resolution is limited to 200 msec because the GPS chip reports at most 5 Hz updates.


From: 'Rod Johnson' via Issaquah Amateur Radio Club <issaquah-arc@...>
Sent: Friday, October 02, 2020 2:55 PM
To: issaquah-arc@...
Subject: Re: [IARC] Groundhog Day #244


That is very cute, but I would rather have the time update on the second...just saying...


It is hard to count down seconds to do a time hack when the numbers displayed do not reliably agree with the actual second; and my Griduino seems to be reliably one second slow at the top of each minute when compared to WWV/WWVH.

It usually pops up 'xx:59' seconds as the tone is heard.  But, sometimes the 'xx :58' is displayed, and sometimes it seems to skip that 'xx:59'  display and go directly to the :00 seconds exactly on the 1 second 'tick'.



-----Original Message-----
From: barry@...
To: edwaynet@...; issaquah-arc@...
Sent: Fri, Oct 2, 2020 1:58 pm
Subject: [IARC] Groundhog Day #244

For your amusement… Every day is Ground Hog day in my household. It’s hard to tell days apart during months of self-imposed isolation. What’s an engineer to do? I’m glad you asked. Every problem, no matter how easily solved with a pencil and calendar, can have an engineering solution. So … I built a visual display into Griduino.

I added a “view” to count the span of days from Sunday, Feb 2, 2020 through the current date and time. Whew! Now I have an easy way to tell the days apart!

A circuit boardDescription automatically generated

In case you’re wondering:
“-7h” is the time adjustment from GMT. “8#” is the number of GPS satellites in view.


Happy Groundhog Day #244,

Barry K7BWH