My father had a HP-45 from work, which had the secret stopwatch mode.
The HP-35S is the only current HP worth buying; eventually I'll get one.
My current main calculators are a HP48G+ (which I bought used since I wanted a 4 line stack display) and a TI-89 -- both are very nice, and I still enjoy using them.
I still have a HP-41C with quad memory and some cool books (including HP-41 assembly language programming). The HP-41C needs its zero key fixed; hopefully I'll get around to that sometime this year. Once it's fixed, I haven't decided what I'll do with it.
My first calculator was a HP-34C; I learned to program on it.
@Antedeluvian, why don't you replace your NiCds in your 35,
I did, twice. But it was expensive. My career progressed to the point where I needed a programmer's calculator for all the binary<->hex<->numerical conversions and I ended up with a Casio for much less than the price of NiCds. The Casios have come and gone though- the HP35 still has a place of pride on my shelf. I now use the HP35s which does meet all my requirmements.
@Sven, in answer to your question, "Are you interested in my recollections...? my answer is a very definite YES. However there will be others who will find your FPGA musings of greater interest. So why not do both and keep everyone happy?
What are the engineering and design challenges in creating successful IoT devices? These devices are usually small, resource-constrained electronics designed to sense, collect, send, and/or interpret data. Some of the devices need to be smart enough to act upon data in real time, 24/7. Specifically the guests will discuss sensors, security, and lessons from IoT deployments.