Why are PI detectors made with MCUs rarely seen?

[hisun]

I am a beginner, and the forum has taught me a lot. However, I have some questions that I hope someone can answer. In the posts, detectors made with op-amps are common, while those made with MCUs are rare. And when MCUs are used, they are typically AVR or PIC chips. Nowadays, ARM can be considered reasonably priced and can implement digital algorithms in use, but why haven't I seen detectors made with ARM? Another thing that puzzles me is that AI told me the detector coil should be small; the larger the coil, the more power it needs. Yet I see some finished products take an extreme approach, with coils several meters in diameter. This obviously conflicts with battery power density and usage time. Is this just a gimmick?
Thank you for any answers. I don't know English and am using translation software, so please ignore any awkward phrasing.

[profesor]

It's normal that you don't see ARM-based pulse detectors. That's because they're mostly used in commercial projects. Presumably, many forum members have high-level projects on their computers. A large coil doesn't consume much power.

[Carl-NC]

...but why haven't I seen detectors made with ARM?

Commercially, most detectors are designed with ARM processors, including some PI. But PIC and Atmel have a much longer history with hobbyists, especially since their tools were free. For a long time, tools for ARM micros were very expensive. It was only 7 years ago that STM bought Atollic and released the free STMCubeIDE. I think more and more you will see ARM chips in hobby projects.

Another thing that puzzles me is that AI told me the detector coil should be small; the larger the coil, the more power it needs.

Don't believe everything AI tells you.

[hisun]

Thank you very much for the answers above.

I still have some questions. Nowadays, ARM has free development tools, so there is no longer a need to use expensive development tools, and programmers are very low cost. That is to say, the cost of development tools for ARM chips is no longer the main issue. Also, personally, I feel that using the discontinuous pulse induction (PI) method for detection seems very difficult to implement with MCU‑based algorithms. Yet in practice, this pulsed PI method is indeed very common. Is it because MCUs in the past were not powerful enough to handle complex algorithms? Or was it to accommodate the use of op‑amps and analog circuits at that time? If algorithms are used for detection, what is the common architecture? I came across a design called QuasarARM that seems to use algorithms for detection, but I don’t understand the function of U1A in its circuit, nor which algorithm it uses for detection. Its circuit diagram is shown below.