Yes, at the time I began working on this, I didn't know. I didn't know that the hardware was open source, I thought it was just the software. As I'd not really done anything with uCs, my "experience" with Arduino was a) spelling it correctly, and b) wasting money on a small kit I never used 15 years ago. My take on its rise to prominence was the open-source software and the ability to program it with C++. Feeling kinda dumb as I proof-read that. But, that's what it is.
Um, so, I followed that link. And I read through parts, skimmed others. I'm pretty sure there's a man with gray, wild hair, who smells of musty books and Brut 33, and wears out-of-style glasses, fully tenured on a campus, who hasn't seen a mall or a Top Golf, who would get giddy about that. "But, if we populate the crystal capacitors with left-handed electrons, the phase shift is 4.56 x 10⁻⁵ Hz!!!" Calvin would say, "The trees are really sneezing today."
I found the calculations presented here on choosing capacitors to be enlightening. I will, however, be avoiding the urge to take 3,000 grit sand paper to the caps to "dial-in" the 0.2 on a calculated 17.2pF target.
I took a while but I finished the design and had the PCBs made. Praise the Lord, they work amazingly well. Considering the amount of Magic Smoke I’ve released from components in the many years I only occasionally tried anything with electronics, this is a huge win and a blessing.
I took suggestions and modified my design. Most notably in the suggestions I want to call out: 1) add ICSP pins and 2) break-out unused pins from the uC.
I had updated a library which I later learned broke my code. A method/function of the library was no longer static and my use of it caused the system to crash/lock. Once I found that problem, having ICSP was priceless to have on-board. Darned good call on that one.
I have additional functionality which I’ve come to realize I’d like to add to this system. I have 8 pins that I broke out which are currently not used. I will be able to use those additional pins to enable that functionality. Also a darned good call. I also chose to add connection pads for the unfiltered 12v input to the system as well as the regulated 5V and the GND which will facilitate adding the new functionality. I only added those connections in light of the paradigm of “make it available now, ‘just in case’”.
I was able to eliminate the crystal and associated caps and am running on the internal 8mhz clock which saved me some complexity and a fair amount of board space.
Notice the use of the DRV8251. I replaced a rather large 5V DPDT relay, relay socket, a MOSFET with that tiny motor controller. This was a huge improvement in my design and one of the largest steps in floorplan savings.
Thank you to those who contributed very useful input. I’ve tested it on the bench, run the motor, blah blah blah. I’m on my way to install this in the field today. I couldn’t have done any of this project without those on this forum who offered helpful input.
