[Coco] Coco Digest, Vol 123, Issue 49

[Brett Gordon]

> On Wed, Apr 10, 2013 at 5:32 PM, Aaron Wolfe <aawolfe at gmail.com> wrote:
>
> > The power situation is a concern.  I believe a lot of the Pi's power
> > requirements are to drive it's USB ports, which would not be in use in
> > the scenario I'm thinking of.. maybe that would help?  I suppose
> > separate power or major changes to the coco is possible, but it would
> > be awfully nice to have something that could just plug into any
> > regular coco.
> >
> > The Pi is just one step in a long road of smaller, faster, cheaper,
> > better..  maybe it's not quite where we need it on some axis.
> >
> > -Aaron
> >
> >
> > On Wed, Apr 10, 2013 at 7:28 AM, Frank Pittel <fwp at deepthought.com>
wrote:
> > > I here a lot about "plugging" a pi into a coco and always wonder if
the
> > coco
> > > power supply has enough power drive it. The specs I've seen shows that
> > the model
> > > A uses 300ma and the model B uses 700ma. That seems like a lot of
power
> > for the
> > > undersized PS in the coco!! One possible solution would be to "dump"
the
> > internal
> > > supply and use a wall wart type supply to power the pi and coco. I've
> > got a couple of
> > > usb supplies that put out 5V at 2.1 amps and I've seen some that put
out
> > 3A.
> > >


> Date: Wed, 10 Apr 2013 21:57:03 -0500
> From: Allen Huffman <alsplace at pobox.com>
> Subject: Re: [Coco] CoCo and Rasberry Pi ( and Software Rant )
> To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
> Message-ID: <49A48319-683A-4BB4-841A-3242F2816725 at pobox.com>
> Content-Type: text/plain; charset=us-ascii
>
> On Apr 10, 2013, at 9:01 AM, Brett Gordon <beretta42 at gmail.com> wrote:
> > Oh yeah the PI is amazingly cheap.
>
> You had me at that part. :-)
>
> > have.  Even after you boot from ROM you get a static enviroment:  both
> > RS-DOS and RBF systems have NO SUPPORT FOR PARTITIONING.  This is
> > stupid. Disk Partition Tables have been agreed upon and in use in the
>
>
> That sounds great. Where do we start?
>
>                 -- Allen


Good point on the Power concern, Aaron.   The keyboard/mouse usb combo I
have plugged into my Pi running on a .7 amp supply looses keystrokes
because of the supply.   I don't thing the CoCo should be powering the Pi.
Maybe a external power supply can power the Pi and the CoCo?   Can we power
the CoCo via the Cart interface ?   Maybe we can have a custom Cart
providing power to the CoCo and the Pi....  It's not hard at all to open
your coco up and detach the internal power supply.   The Pi can be powered
via the GPIO headers.

Another issue is that only the USB part of the Pi uses 5 Vdc the rest of
the system, including the GPIO pins use 3.3 Vdc...  So any CPLD should be
able to translate the voltages.

I know nothing of CPLD design (allthough I understand the basic idea)...
Cloud-9's SuperIDE is an existing design that is very,very similar,  so I'm
sure this can be done.  The rest of the problems are just the normal ones:
A cart case, a cart board, a CLPD development board,  etc...

Here's an interesting Idea:  How about a 8k or 16k sram chip rather than
Flash Rom?  If the Pi/CPLD could team up and hold the HALT or RESET line
low on the CoCO until it has loaded the cart's SRAM with a ROM image from
it's SD card... then it would release HALT ( or RESET ) and let the CoCo
boot from that ROM.

Maybe the CPLD can do the SRAM too ?


--
Brett M. Gordon,
beretta42 at gmail.com