[Coco] [COCO] Raspberry PI and CoCo Cart

[Aaron Wolfe]

I have been wanting/planning/trying to gather information on a "Pi in
a Pak" for some time now.

Interfacing via a faster, less CPU intensive DriveWire connection is
interesting, and maybe that is the limit of what can be done.
However, I had hoped for something a bit different.  I've talked with
some experts (or at least they know a heck of
a lot more about it than I do) and gotten some ideas but maybe the
list has some too...

It seems like the ideal (and maybe unobtainable) interface would be
one which can read and write directly to the
bus lines just like a regular ROM pak or drive controller.  Given this
ability, one could accurately simulate *any*
pak or peripheral (or several at a time?).  You could also create new
peripherals, such as interfaces to the various
I/O found on the Pi (USB, ethernet, audio/video, etc...).   Way better
than an embedded DW server imho.

I don't know if its possible or practical, I just know that it would
be awesome.  From what I've gathered... it might be possible
but it's not a sure thing.  You have to dance pretty fast to play on
the bus.  The Pi does have an SPI interface capable of many
Mb/s throughput (one guy's testing says 16Mbps is a practical limit)
in addition to several GPIO pins.  John Kent showed me
a cheap I/O processing chip that was cheap, programmable, had SPI and
a whole bunch of latches, and could operate in the
multi Mhz range.  Can they be stuck together into something that can
participate on the coco bus?  I wouldn't even know how
to guess, but I'd surely like to find out.  Also interested in
alternate schemes that provide superior/more direct communication
than the DW style serial line.

Can the Pi be turned into the ultimate virtual MPI?  $0.01 for your thoughts




On Fri, Oct 5, 2012 at 7:09 PM, David Ladd <drencor at gamepixel.net> wrote:
> One of the things I was thinking is with the cart side is having two
> FIFO chips to buffer data between the Raspberry Pi and the CoCo.
>
>
> On Sat, Sep 29, 2012 at 5:58 PM, Aaron Wolfe <aawolfe at gmail.com> wrote:
>> On Fri, Sep 28, 2012 at 10:42 AM, Brian <briang0671 at sbcglobal.net> wrote:
>>> On 09/28/2012 12:05 AM, David Ladd wrote:
>>>>
>>>> Here is a interesting idea I just had.
>>>>
>>>> What if we were to interface a Raspberry PI and have it connected to a
>>>> CoCo cart so you could take advantage of the Boisy Interface/Becker
>>>> port so that you could have faster access to drivewire 4 server?
>>>>
>>>
>>> What is the Boisy Interface/Becker port?
>>>
>>
>> This is a fifo buffer interface implemented initially in the CoCo3FPGA
>> project and since ported to some emulators.  It allows DW to operate
>> at very high speed/low cpu use compared to bitbanger on those
>> platforms.  OS9 modules to support the interface are in the NitrOS9
>> source.
>>
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