[Coco] Flash updated Dragon DOS into SDC... help!

Rogelio Perea os9dude at gmail.com
Sat Mar 12 14:09:19 EST 2016

Thanks for the disk offer Pere, but it won't be necessary... managed to get
the 2503 update flashed into the SDC :-)

I did try to use the updater VDK file as it is released but on the Dragon
DOS/SDC release I had on my card, the WRITE commands of the BASIC updater
program came off as unrecognized tokens, flagged by ! characters.

I also tried to snoop out the BIN file LOADM address out of its preamble,
but being it a data file more than an executable binary program, I hinted
that the preamble calculated load address would be meaningless, the length
reported on the file with the 'preamble' read as is was even more out of
bounds than the 'load' address - the update BIN file did have the codes for
characters D and K properly set on the first two bytes - a Disk ROM file.
More on this later...

Ended up writing a small BASIC program  to use on the CoCo I was putting to
the task of flashing the new DOS onto the Dragon card (properly set to be
used on the CoCo for the programming purposes of course). A simple routine
to read the BIN file from the DSK image byte by byte and POKE it the same
into an area of RAM chosen to do so, in my case I was starting everything
at &H3000. First attempt to flash the RAM contents worked as far as the
WRITE MEM at 3 command I was issuing (using the third flash bank) but once set
back in the Dragon nothing happened... couldn't get it to work.

Went back to the DSK installer image created with CoCoDskUtil and taking a
look at the Hex Editor built in I checked on the updater BIN file. It
indeed had the characters D and K at the first two bytes but in their
lowercase representation, after that there were like &100 bytes or so of
apparent gibberish until offset &H0107 the codes for uppercase D and K were
seen, more proper code seemed to follow from that point forward. Edited the
BIN file to trim everything off from start to the noted offset and while
doing that also checked on the "tail" of the BIN file, a lengthy series of
zeroes followed the end of what I took as valid ROM code... trimmed the end
as well.

With the slightly shortened updater BIN file I updated the DSK image and
set that to run with my ML transfer routine, issued the WRITE command for
that memory block into the SDC flash, reset the SDC for Dragon use, into
the Dragon port and I got the banner for the 2503 release of your DOS code.

Been playing with the Dragon setup all morning, no problems found on any of
the VDK images loaded. Now any updates should be a cinch to do using the
Dragon - heard 2504 is out... later.

I am not sure how the BIN updater file in the 2503 distribution VDK got
such padding at its start and end... MS Windows?

It was fun, that's all I can say :-)

-- RP

On Fri, Mar 11, 2016 at 4:15 AM, Pere <psergm at gmail.com> wrote:

> Hi Rogelio,
> If you have my last VDK file (something like "DW42 v0.25.03
> SDC-Updater.VDK"),
> it should be a 184k disk, ready to work an a Dragon.
> You don't need to use the CoCo any more to flash a bank for your Dragon.
> You could simply copy the VDK in the root of your card using  ashort name,
> for
> instamnce "INSTALLER.VDK"
> Then you mount it:
> And issue a DIR command to see the VDK contents
> There should be a basic program: "UPDBANK.BAS" and the file "UPD2503.BIN"
> You run the BAS and choose the desired bank where the program will install
> the new extender version ... that's all!
> Hope it helps
> cheers
> pere
> PS If you don'thave that disk,  drop me an email and I will send it to you

More information about the Coco mailing list