Unveiling 9 Surprising Quirks in Raspberry Pi Pico's PIO Programming

The Raspberry Pi Pico’s Programmable Input/Output (PIO) subsystem, while powerful, has some unexpected behaviors. PIO allows for precise, low-level hardware control, performing as efficiently in MicroPython as in Rust or C/C++. It’s versatile, enabling custom peripheral interfaces without additional hardware complexity. However, PIO programming has its quirks. For instance, the Pico’s state machines, despite their name, are not traditional state machines but tiny programmable processors with their own instruction set, processing one instruction per clock cycle. The Pico 1 runs at 125 million cycles per second, while the Pico 2 runs at 150 million cycles per second. PIO provides only two general-purpose registers, x and y, forcing programmers to be strategic with their use. A challenge like creating a backup beeper with a 1000 Hz tone for 1 second, followed by 1 second of silence, requires clever use of loops and special-purpose registers like osr and isr. Moreover, PIO programs are limited to just 32 instructions, necessitating efficient coding. Understanding these quirks is crucial for effective PIO programming, as demonstrated by the development of a theremin-like musical instrument.

Source: towardsdatascience.com