Ah interesting! I work on (very expensive) SDRs and we make pretty heavy use of Xilinx Zynq Ultrascale SoCs. They combine Cortex-A, Cortex-R, and FPGA fabric all in one package, with some fancy interconnects. So you can handle the hard realtime stuff on an RTOS or in the FPGA, then send the data over to the application processor with a hard float ALU to crunch some numbers (or build some kind of dsp IP into the FPGA, idk much about that side of it).

I've also seen some cool stuff with the BeagleBone products, which have a few TI custom architecture DSPs and "realtime units" which you can communicate with via Linux.

But yeah, I can certainly see how just doing it all on a super fast MCU could be easier and cheaper without the backing of commercial enterprises.

I've always thought it would be cool to design a "poor man's zynq" hat for a SBC. Stick a RP3050 and a Lattice FPGA on there and set up some SPI / UART connections.

Nah, it's a spectrum. Companies like NXP and Infineon are at one end. NXP wants a ton of personal information to access even the most basic docs on some of its chips, sometimes even an NDA. Infineon won't even acknowledge you for the most part.

Companies like STM, RP, and TI are at the other end. STM got super popular because they're cheap and the documentation is incredibly easy to get at. I think RP is following suit.

Renesas puts out some documentation, but it's really rough. Anything that has even a whiff of crypto is completely undocumented. They're also squatting on a few Rust crates where Espressif actually hired a Rust developer to work on their Rust HAL. The most comical thing is that while they version their reference manual they don't seem to update it and instead issue a ton of broad errata that apply to multiple manuals.

Before the acquisition Atmel's documentation was well written and organized.

Yes, obviously, but they don't make the chips, so can't you just source the exact same chip, make thing pin compatible and call it a day? Then you'd have a drop in replacement, any changes you make will cause disruption for people downstream.

https://www.nxp.com/part/MIMXRT1062DVL6A

Spinning an IMXRT1062/IMXRT1064 design sans the terrible Teensy bootloader should take a day or two at most.

These chips have perfectly-fine ROM USB bootloaders and SWD, don't ruin them by adding extra garbage.