Isn't a standalone PIO literally just a microcontroller?
You may have fun playing around with a Parallax Propeller MCU. Rather than have a bunch of peripherals, the Propeller has 8 CPU cores. The idea is that you implement whatever peripherals you want by dedicating cores to the purpose and bit-banging it. It's a similar idea to a PIO, but rather than having a main core and a bunch of tiny cores, you just have a bunch of equally capable cores.
You may have fun playing around with a Parallax Propeller MCU. Rather than have a bunch of peripherals, the Propeller has 8 CPU cores. The idea is that you implement whatever peripherals you want by dedicating cores to the purpose and bit-banging it. It's a similar idea to a PIO, but rather than having a main core and a bunch of tiny cores, you just have a bunch of equally capable cores.