Not FPC, but my compiler https://github.com/t-edson/PicPas supports the more ridiculous minimalistic PIC microcontrollers like the PIC10F200.
At that level I'd probably just write it in assembler or the company C.
I do like that device. But probably too lean for the application and I'd have to add peripherals to that to do what I need to do.
Thx!
Apart of the @Edson's PicPas solution which is not FPC but is a Lazarus project and a Pascal language non the less, there is another free Pascal solution which programs from PIC12F to the fat-est PIC18F, named Pic Micro Pascal. Both of them program families of microcontrollers not supported by FPC. Both well optimized.
If your choice is AVR (ATmega, ATtiny) then the only free, non-limited Pascal compiler might be FreePascal but, if you can use BASIC instead, there is Great Cow Basic compiler that manages both PICs and AVRs with better results.
Back to PICs, Jalv2 compiler (JAL language, similar to ADA?) and Great Cow Basic have always support for the latest (most recent) PIC microcontroller with a great library of functions for all the internal peripherals and a plethora of external devices, with tons of application examples. And great communities.
If you want to try PIC24 and dsPIC33 families (which sometimes are a better choice than many ARM counterparts), then the best solution is Firewing Basic (similar to Visual Basic language) - free and non-limited (it converts BASIC to C language which is then compiled by a full featured C compiler, delivered in the package). You can have access to more PIC24 and dsPIC33 micros (otherwise I would have recommended other BASIC compilers) than are included in the package, but you have to develop your own libraries. Regardless, you have access to a free, fully optimized solution.
Regarding FPC, I would recommend you to experiment with a cheap Nucleo STM32 board, even if overkill for your project. It has a programmer on board and enough FLASH memory for your programs. In my view, is a better solution than a Pico. Yeah, in my opinion, a Nucleo board is best suited for FPC. Support? I think the STM32 family is the best represented...