Paul Koning paulkoning at
Wed Feb 3 18:54:11 CST 2021

> On Feb 3, 2021, at 5:37 PM, Peter Corlett via cctalk <cctalk at> wrote:
> 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...

Yes, I noticed the usual suspects are out of stock.  Need to look further.

My reaction was similar.  I like the dual CPUs, that means one could do hard real time stuff like wiggling I/O lines (for example DDCMP at a megabit per second) while the other does buffer management and talks USB protocol.  I didn't even realize there's a small I/O coprocessor, that's neat.  The TI engine in the BeagleBone Black has that sort of thing (a much larger one) which seems very useful if the job is particularly hard.  David Gesswein made great use of that for hard drive emulation.  But that's a much larger and more expensive solution.


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