[Coco] Micro SD CoCo
operator at coco3.com
Wed Oct 21 00:27:36 EDT 2009
Well folks, tonight I have the CoCo's first Micro SD pak. This is
the same wireless pak model but with a different module plugged into
the header. I just DSKINI'ed DRIVE 0 and saved 2 BASIC programs,
typed DIR, and there they are.
In case you have never seen how small a Micro SD card is... it's
about the size of your pinky finger nail. The module it slides into
is also small and plugs into the Serial Pak's header but needs an
adaptor to match the pins. Imagine hundreds of floppies, thousands
of games and programs, and a full NitrOS-9 system instantly on power-up.
This is a serial-based virtual floppy system (CoCoNet) which works
much like DriveWire, only there are no wires and the virtual drives
are right there in the pak on that little memory card. I'm using a
2gig card for my tests.
The catch? The CoCo talks to the module @ 115200 bps over the 6551,
so there will be some hard-coded Disk BASIC programs that require a
real floppy controller and obviously won't work with a virtual drive
system, but most programs DO run just fine.
I'm still fiddling with how to parition a card to share between Disk
BASIC, OS-9/NitrOS-9 and whatever else. 2 gigs is an enormous amount
of space for a CoCo system, so even if I have to use 1/2 of the
card's 512-byte sectors, we're still good, although I don't want to
waste any space like that.
In case you didn't read right... imagine a little game-pak sized
cartridge with virtually everything for the CoCo on it! This will be
the case when the pak is finished.
The EPROM "firmware" is a patched copy of Disk BASIC. It needs
further tweaking to allow a mix of Drive Pak, Wireless Pak (either or
both) without conflict, in a plug-and-play fashion. The CoCo will
detect which pak(s) are inserted and communicate with the right
module or PC server using the same protocol while allowing serial
communications as well. Take a Serial Pak and plug what you want in
the header, a bluetooth module or Micro SD module, and the pak should
"work" as you expect using the same EPROM with no configuration.
Existing Wireless Pak users could swap out their bluetooth module
with this Micro SD module and pop in the CoCoNet EPROM and be ready,
or keep the wireless pak and insert a drive pak, but the paks need
their own address, so the code has to detect which addresses/paks are
present and automatically set things up when you turn the CoCo on.
As for NitrOS-9... I already have this booting over CoCoNet
wirelessly so I'll just replace the protocol so that either a PC
server or the MicroSD module will work the same... read and write sectors.
I do need to send off for a run of small header adaptors so the
module will fit the Serial Pak. The header just matches a 1x5 header
to 2x6 header, so it's going to be a tiny board with 90-degree
headers on either end and some traces between some of the pins. In
my test I use a breadboard with 4 wires run to it from the Serial Pak
header. Ground, Tx, Rx, VCC. That's it.
~ Roger Taylor
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