It is, at once, both over my head and very encouraging that someone who hasn’t used PIO before was able to achieve this, thanks for the link, I think if I compare this code to what the Plasma library is doing I might be able to tease out what’s happening.

Did you have a look at chapter 3 of the Raspberry Pi Pico C SDK already by the way? It's about PIO programming.

https://www.raspberrypi.com/documentation/microcontrollers/c...

I did not notice they wrote a whole book on the SDK, this looks perfect, thanks again

The C SDK contains examples, the actual documentation is in the RP2040 docs. It's also chapter 3.

https://www.raspberrypi.com/documentation/microcontrollers/