Bringing The PIO To The FPGA

We’ve seen some pretty incredible hacks using the Raspberry Pi 2040. However, one of the most exciting bits of hardware onboard is the Programmable I/O (PIO). Not content with it just being a part of RP2040-based projects, [Lawrie Griffiths] has been porting the PIO to Verilog so anyone can enjoy it.

This particular implementation is based only on the spec that Raspberry Pi provides. For assembling PIO code, [Lawrie] uses Adafruit’s pioasm assembler they use for their MicroPython framework. There’s a simulator to test different programs, and the project targets the Blackice MX and the Ulx3s. A few example programs are included in the repo, such as outputting a pleasant guitar note over I2S and driving a chain of WS2812s.

The project is still incomplete but slowly making progress. It’s an incredible feat of reverse engineering. While the simulator can be used to debug programs, step through instructions, and inspect waveforms, the ultimate value of bringing the PIO to other systems is that now we can re-use the code. Things like the can2040, an implementation of the CAN bus protocol using the PIO. Or even a PIO-based USB host.