Steven McDonald's ZX81<=>PC Converters [Version 3.0]
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This is Version 3.0 (Final) of my ZX81 converters. 
At the time of writing I believe all bugs to have been fixed and the
programs work as expected.

My enocder ZXC.EXE will take a .p file and generate a RAW type wav file at
22050Hz in 8 bit mono (unsigned). Playing this file back over your
soundcard and either recording it to tape or playing it directly into a
real ZX81 - will indeed LOAD the program.

My decoder ZXD.EXE will take a sampled RAW type wav file at 22050Hz in 8
bit mono (unsigned) and decode it to generate a .p file that will work on
the ZX81 emulators... How do you generate the RAW WAV file in the first
place??

Easy... You take your cassette player and play the tape into the LINE IN
on your PC soundcard and start up your favourite sampling program and
record it digitally onto disk! Make sure you tidy up the start and end
to cut out the buzzes/spikes/noise etc. give it half a second of silence or
so before the signal starts and end it just after the program finishes
playing... You should also NORMALISE the signal to make sure it is of high
enough gain for my routines to distinguish signal from no signal!

Save the file as XXX.RAW by the way not .WAV - most sampling software gives
you this option - to save a RAW type file - its basically a WAV file
without all the header information - just the RAW bytes of the sample...

There is a -p option for 'problem tapes' - this sometimes has success if
you are getting corrupted data from a bad tape copy etc.

Please provide feedback on this option and whether you needed to use it
or not!

All programs support -q for quiet. Depending on your CPU speed - this will
speed up the routines. At present a fixed delay is used. On my PII 300Mhz CPU,
I get realtime PC Speaker output. I have just added a new -s option for slower
cpu's - give it a try if you have a slower machine.
Feedback welcome on this issue as well!

So what else is new in this release?

Quite a lot. I did a major restructuring on the code, added new options
and fixed a lot of bugs.  Internally, ZXC and ZXD are much more alike now
which makes maintenence easier!

ZXC now reports on the main ZX81 system variables etc. as well.

Fred Nachbaur pointed out that my converters where no use when running in a
DOS batch file - handy for long overnight processing on slower cpu's!
I have now added a new -b option to both programs - this cuts out all waits
for kepresses and jumps past the intro screens etc.
So, you can now write a batch file something like:

BIGJOB.BAT:

@cls
@echo off
ZXD fortynin.raw -q -b
ZXD rocketmn.raw -q -b
ZXD booster.raw -q -b

etc.

Goto bed and leave it overnight with no sound to annoy you ;-)
Hopefully, when you awake, all the .p files will be sitting waiting for you!

Another new addition is that both ZXD and ZXC now generate the appropriate
named output file based on what you use as the input file - instead of
just using ZX81.???

So ZXD rockcrsh.raw will automatically generate rockcrsh.p
and ZXC dansrvng.p will generate dansrvng.raw for you.

I added new intro screens to both programs that can be seen as long as you
are not in batch mode.

I added proper support into both programs for tape files over 16K in size.

At the DOS command line, just type in either programs name with nothing else
for a list of supported options and syntax etc.

Please contact me at zx81@stevemcd.easynet.co.uk if you have any problems.

Please do not re-distribute these programs. Instead point people to my
website.

Thank You.

Updated versions available at:
http://surf.to/zx81 or http://easyweb.easynet.co.uk/~stevemcd/zx81.htm

I am keeping the source code private for now but if you really need
to see it - you can always ask ;-)

Steve McDonald (18/01/99)