RE: OO Library to handle Pico PIO relative interrupts: usage and example

Jan Cumps — Wed, 17 Dec 2025 21:21:09 GMT

I like to be confident of my designs - but I've been around [emoticon:c4563cd7d5574777a71c318021cbbcc8].

Dealing with real time and frequent interrupts can be challenging.
I'm using an OO design here - an approach that's often flagged as risky for embedded designs.

I trust the code, but prefer to back that up with real world data.
I tested this design on a RP2040, and an RP2350 (in ARM and RISC mode), for a month.

With all PIO state machines used (8 on a RP2040, 12 on a Pico2), there was not a single interrupt missed, and no memory leakage.
I also tested this with fewer than max PIO state machines deployed. The code has behaved stable all the time.

It shows that C++26 and GCC are stable. But it also shows that the Pico controllers - and the Raspberry Pico SDK, are sound.

RE: OO Library to handle Pico PIO relative interrupts: usage and example

Jan Cumps — Fri, 07 Nov 2025 16:50:06 GMT

In the example that I attached to the post, I program each PIO, and initiate each state machine individually:

[embed:dc8ab71f-3b98-42d9-b0f6-e21e02a0f8e2:df5cc185-7d76-43b4-beeb-0a4ab61e700a:type=c_cpp&text=%20%20%20%20%2F%2F%20program%20each%20PIO%2C%20and%20initialise%20each%20sm%0A%20%20%20%20uint%20offset%20%20%3D%200U%3B%0A%0A%20%20%20%20offset%20%3D%20pio_add_program%28pio0%2C%20%26run_program%29%3B%0A%20%20%20%20run_program_init%28pio0%2C%200%2C%20offset%29%3B%0A%20%20%20%20run_program_init%28pio0%2C%201%2C%20offset%29%3B%0A%20%20%20%20run_program_init%28pio0%2C%202%2C%20offset%29%3B%0A%20%20%20%20run_program_init%28pio0%2C%203%2C%20offset%29%3B%0A%20%20%20%20offset%20%3D%20pio_add_program%28pio1%2C%20%26run_program%29%3B%0A%20%20%20%20run_program_init%28pio1%2C%200%2C%20offset%29%3B%0A%20%20%20%20run_program_init%28pio1%2C%201%2C%20offset%29%3B%0A%20%20%20%20run_program_init%28pio1%2C%202%2C%20offset%29%3B%0A%20%20%20%20run_program_init%28pio1%2C%203%2C%20offset%29%3B%0A%23if%20%28NUM_PIOS%20%3E%202%29%20%2F%2F%20pico%202%0A%20%20%20%20offset%20%3D%20pio_add_program%28pio2%2C%20%26run_program%29%3B%0A%20%20%20%20run_program_init%28pio2%2C%200%2C%20offset%29%3B%0A%20%20%20%20run_program_init%28pio2%2C%201%2C%20offset%29%3B%0A%20%20%20%20run_program_init%28pio2%2C%202%2C%20offset%29%3B%0A%20%20%20%20run_program_init%28pio2%2C%203%2C%20offset%29%3B%0A%23endif%20%20%20%20]

When you use the c++ standard library, you could do this differently.

[embed:dc8ab71f-3b98-42d9-b0f6-e21e02a0f8e2:6acc9203-6fb8-4012-a934-8dc06e21420f:type=csharp&text=%20%20%20%20%2F%2F%20program%20each%20PIO%2C%20and%20initialise%20each%20sm%0D%0A%20%20%20%20for%20%28uint%20u%20%3D%200u%3B%20u%20%3C%20NUM_PIOS%3B%20u%2B%2B%29%20%7B%0D%0A%20%20%20%20%20%20%20%20uint%20offset%20%20%3D%20pio_add_program%28PIO_INSTANCE%28u%29%2C%20%26run_program%29%3B%20%0D%0A%20%20%20%20%20%20%20%20for%28auto%20%26h%20%3A%20handlers%20%7C%20std%3A%3Aviews%3A%3Afilter%28%5Bu%5D%28const%20auto%26%20h%29%7B%20return%20h.pio%20%3D%3D%20PIO_INSTANCE%28u%29%3B%7D%29%29%20%7B%0D%0A%20%20%20%20%20%20%20%20%20%20%20%20run_program_init%28h.pio%2C%20h.sm%2C%20offset%29%3B%0D%0A%20%20%20%20%20%20%20%20%7D%20%20%0D%0A%20%20%20%20%7D]

This uses a range filter. It 'll only return handler objects assigned to a particular PIO.

For each PIO, it

programs that PIO
checks the handler container if there are any state machines for that PIO
if yes, initialises those state machines

This is all embedded friendly. Each option has its pros and cons. But no excessive resource usage - this is all cheap on the cycles.

opinion?

RE: OO Library to handle Pico PIO relative interrupts: usage and example

DAB — Thu, 28 Aug 2025 20:43:22 GMT

Great post Jan.

I am curious, do you have an implementation that actually uses seven stepper motors?

RE: OO Library to handle Pico PIO relative interrupts: usage and example

Jan Cumps — Wed, 27 Aug 2025 21:11:59 GMT

[mention:f92905a7470f4b3e9f2dbfcd6cdd918f:f7d226abd59f475c9d224a79e3f0ec07]