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Comment by fpgaminer | Hacker News Reader

> but the PIO does seem to be a very useful feature.

Back in the early days of RasPi there was a competitor, the BeagleBone Black. It was similar to the Pi in many ways, but included embedded MCUs that were meant in much the same ways as the Pico's PIO. You could use them to bitbang protocols that would be difficult/impossible/unreliable to run on the SoC itself.

I thought it was a brilliant idea, but the BeagleBones never got the same level of support that the Pi did. The few times I tried using my Black, I ran into numerous deal breaking bugs.

It's great to see the spirit of this idea is still alive and well. I've got my fingers crossed that they somehow convince Broadcom to build PIO into their SoCs.

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The PRUs were really hard to use. I think if they had invested in dev tools with a shallow learning curve, like Arduino support for the PRUs, they might have gained critical mass.

The Beaglebone Black was pretty nice compared to contemporary Pi's for embedded work: way more GPIO pins, with female headers rather than male (lower chance of accidental short circuits; easier to just jam components or wires in there like it's a breadboard.)

Indeed. Ken Shirriff wrote about using the Beaglebone's PRUs:

https://www.righto.com/2016/08/pru-tips-understanding-beagle...

This is great. Is there some tutorial of this caliber for Pico's PIOs?

The Pico’s official documentation seems leagues better than what the PRU’s offer(ed).

Check official documentation of the RP2040 and see if you like that. It's chapter 3.

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

Some interesting excerpts:

There are two PIO blocks with four state machines each.

Each state machine, along with its supporting hardware, occupies approximately the same silicon area as a standard serial interface block, such as an SPI or I2C controller.

Making state machines programmable in a software-like manner, rather than a fully configurable logic fabric like a CPLD, allows more hardware interfaces to be offered in the same cost and power envelope. This also presents a more familiar programming model, and simpler tool flow, to those who wish to exploit PIO’s full flexibility by programming it directly, rather than using a premade interface from the PIO library.

There's a possibly-DOA project called BeagleV to produce a modern 1 GHz-class board running a RISC V system.

I'm sad that the beaglebone didn't "win" versus the raspberry pi. I have several Beaglebone Blacks and they're great little devices, even if the PRU is a little hard to use.

The BeagleBone is the basis for some really cool audio tech - https://shop.bela.io/

Bela includes a xenomai based linux distribution which gives you a hard realtime OS for audio whilst normal linux running as a xenomai task, so you get all the normal productivity and development tools, but your audio is able to run at really low latencies compared to 'normal' OS support.

The Black is low power by todays standards, a single core @ 1Ghz I believe, but it's plenty of power for many audio apps, and boots within seconds, so ideal for embedded applications.

The best part of the BeagleBones, in my opinion, was the onboard eMMC. Soooo much more reliable than running from sd cards at "scale".

In a former life, we had around 1k BB Blacks and 2k BB Greens deployed in greenhouse automation devices before that startup went bankrupt.

The processors were rather under-powered compared, but generally up to the task. Great little devices.

A project similar to this one for the Beaglebone Black:

http://beaglelogic.github.io/

I remember a lot of fanfare around the BeagleBone models, that was in the time in my career I was focused mainly on software / webdev. I remember there was even a $10 model, but IIRC there were some fulfillment issues?

Yes, there are still fulfillment issues, the Octavo SoC is nowhere to be found. As a product, the PocketBeagle is better and lower energy consumption than the Pi Zero. You could both power it and access it from USB, it has two CAN bus ports and 4 UARTs. I couldn't ethernet + power over a single USB cable to work on the Pi Zero, yes on the PocketBeagle it works out of the box. But then the Pi Zero added WiFi, the mode powerful and energy hungry Pi Zero 2 W, while the PocketBeagle continued to have fullfillment issues and it has probably gone past $50.

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