Greaseweazle

[Peter Corlett]

On Wed, Feb 03, 2021 at 01:09:50AM -0800, jim stephens via cctalk wrote:
> On 2/2/2021 11:51 PM, Peter Corlett via cctalk wrote:
>> The Raspberry Pi Pico has a similar price to the Blue Pill and seems a
>> much better machine for this task, although I haven't combed through its
>> reference manual yet.
> For capture and writing (if that's part of the design) I heard there's a
> dedicated coprocessor for the GPIO pins. It might be useful for offloading
> some of the proccessing from some external circuitry to do the capture or
> output.

I have now pulled the reference manual to look at the GPIO stuff, and it is
indeed very shiny. There's only space for 32 coprocessor instructions per
GPIO bank, but that's possibly all you need: it is apparently possible to
implement a full UART with handshaking in that.

Controlling a floppy is broadly the same level of complexity as a UART, so
it seems that the Pico would be he perfect tool for the job. Now if only I
could actually lay my hands on one...

> I don't know what's included for the capabilities. And apparently since
> the chip is new, there's only assembler programming for it now.

It's a Cortex M0, so any compiler which can produce freestanding ARM code
can generate code for it. So that's gcc, clang, rustc, etc. I suspect I can
just use my existing embedded tooling after telling it to use a different
subarchitecture.

> There's a video comparing the Pico, ESP32, ESP32-S and Blue Pill. The latter
> was a bit low in resources compared to the others.

OTOH, I can actually buy a Blue Pill today from reasonably reputable local
suppliers such as Amazon or AZ-Delivery, and they only cost €15 for five
including delivery. The Pico will be a game-changer if/when there's actual
stock here on the Continent. Importing directly from the UK is no longer a
sensible proposition.

> I'll try to find it and post it if anyone's interested.

No rush, especially as I only suffer video as a last resort when information
is unavailable in any other form.