555 Timer Circuits

Plenty of people are commenting on how modern microcontrollers are better than the 555. I agree, with a caveat: the 555 is a great learning tool. It is complex enough to be interesting, yet simple enough to be well understood. It is easy to clip an oscilloscope to it's pins to have a visual representation of how its inputs affects its outputs. It is a stepping stone that helps people learn how to build more complex circuits. Much as some software developers have to understand assembly language to build the most fundamental bits of software (e.g. compilers), some people have need to understand electronics to build the most fundamental bits of hardware.

I always found DACs/IO to be the limiting thing with microcontrollers. That and latency in general. When you were doing analog stuff with op-amps, yeah, you were setting yourself up for other problems like thermal drift, but there was never any worry that you were going to run out of capacity like you would switching tasks on a microcontroller, and latency was negligible. Plus there weren't many wires and you could see it on a scope. It was all satisfyingly immediate. I wonder what kind of cheap and ubiquitous DSPs(?) people use for that kind of niche nowadays, to do it digitally(?). Do they string DACs together on a bus somehow? How do you get, say, signals flowing around at a couple hundred kHz sample rates, with nice dataflow parallelism -- and then get those signals out to actuators, without much latency -- in that world? Like, what would you use to mix a bunch of audio and run some IIR filters with 20ns latency? Or control, say, four motors with, I dunno, 1 kHz bandwidth? I get this feeling that DACs remain a bottleneck and you're rapidly looking at expensive stuff to do that with a microcontroller, but maybe I'm wrong; I don't do this stuff.

As an FPGA developer: much agreed. We know exactly what's happening every clock cycle (or at least can), and often are able to have extremely deterministic computation. You can do this on micros, but anything with good performance will have some caching, maybe context switching, etc. The polarfire SoC marketing has a graph showing either determinism or performance (I can dig it up if interested). In FPGA land, we define the pipelining such that we get both. I usually go out to an RFIC then stop caring, but you can calculate the latencies the as well.

I'm not an expert by any definition of the term, but a book on programming for the Raspberry Pi Pico with Micropython recommends the MCP3008 ADC.

Only problem is that an oscilloscope isn't accessible to beginners. It's a specialist piece of equipment that takes time to learn how to use, and are furiously expensive at best for someone who doesn't know they might like electronics to buy. That's fundamentally why people are lauding the benefits of microcontrollers, figuring out what's wrong with one doesn't require an O-scope.

Indeed. An intuitive, easy to use oscilloscope needs at least to be digital and hence expensive. An alternative is using an electronics workbench simulator, but then again you might as well go fully digital.

When circuits become larger than trivial, the analog way is noise and temperature sensitive, you will spend a lot of time on tweaking those aspects by themselves.

That really depends upon the context. Many learn electronics in a classroom environment. Even for those who learn electronics independently, it has been possible to get new oscilloscopes that work at audio frequencies for well under $100 for many years. It looks like scopes that operate upto 20 MHz have been available for under $100 for a couple of years. They aren't great, but they are still powerful tools for learning.

And while scopes do take time to learn, learning about scopes themselves will convey a lot of fundamental information about electronics. I also wouldn't underestimate the difficulty in learning how to use microcontrollers. While using something like Arduino (boards, shields, development tools, and libraries) may be straight forward, the learning curve rises steeply as soon as you try to do anything truly independently. More steeply, I would suggest, than learning how to use an osilloscope. Besides, most of those development boards cost a lot more than a bare chip.

Fpga's have the best of both worlds!