Prev: PILOT cartridge (crt-file) for Commodore 64 (C64)
Next: Connecting Philips CM8833 monitor to C64
From: Jonno Downes on 25 Jul 2010 07:36
just curious as to what (if any) custom kernals existed (or even,
still exist)?
I know about speed loaders like Jiffy DOS, but was there anything more
extreme? e.g.
- monitor / debugger in ROM?
- replacing BASIC ?

I've seen a fair bit of custom ROM images for the apple 2 ("crack
ROMs" etc as well as industrial control firmware) but not so much for
the c64 - maybe any custom code like that ended up in a cartridge
instead
From: Andreas Meerbann on 26 Jul 2010 03:36
Hi Jonno,

I once worked for a small local and ultra-low-budget Radio Station and
the needed a radio controled clock on a video output. So I bought a
receiver module, connected it to an old 64's user port and wrote a
small program to decode the clock and display it in a nice way on the
64. The problem was that you had to load the whole stuff again from
disk/tape after power outage and these days this was already quite
uncommon to all the late Amiga/early Win31 kids that hung 'round there
and nobody was really keen on doing that manually. So I had the idea
to burn the program on a module and plug that into the expansion port.
But then I though - since the 64 was doing nothin else than that - it
was easier to burn it into the Kernal ROM directly - So that special
64 came with a very special Kernal ROM that could just decode the
radio signals and display a nice clock.
Don't know how long that 64 was in operation but I was definitely for
some years. Some weeks ago I even found some EPROMs with older
versions of that software in a carton box in my basement. Maybe I
should plug it into my 64 to see if it's still working but I don't
have a receiver module right now.

Is that custom enough???

cheers,
Andi
From: Jonno Downes on 26 Jul 2010 06:39
On Jul 26, 5:36 pm, Andreas Meerbann <andij...(a)gmx.de> wrote:
> Is that custom enough???

I'd say that would qualify :-)

Can you explain a bit more how the receiver worked? Was there a radio
signal broadcasting some kind of digital time signal?
From: Andreas Meerbann on 26 Jul 2010 08:43
Hi Jonno,

> Can you explain a bit more how the receiver worked? Was there a radio
> signal broadcasting some kind of digital time signal?

yes, sure:
here in Europe we have long wave transmitters in countries like
Germany, UK, France... . These are broadcasting clock pulses that have
been derived from an atomic clock. My receiver module was tuned to the
German transmitter DCF77 (see here for details: http://en.wikipedia.org/wiki/DCF77).
In that wikipedia article you can see such a module (second picture
from above) - I bought mine in an electronics shop for maybe 10
Deutschmarks which are now 5 Euros.
Each clock puls is either 100ms or 300ms long representing a "1" or a
"0" bit. So within one minute there are 60 bits which encode the time,
date, daylight saving time status und other information (I think
weather forcast AFAIR).
These signals are very handy to build a very exact clock that never
needs to be adjusted to the correct time since it learns the time from
that signal. Thanks to cheap eletctronics these clocks have become
quite popular and are available in all kind of types from as wrist
watches over alarm clocks until "train station"-type clocks. There are
even modules or PCI-cards you can plug into a server computer which is
then always running on the correct time. The broad range of products
is maybe the reason why such an antique technology is still up and
running in the 21st century.

For the 64 I had to attach the module to the user port (power supply +
1 data bit). Since the setup would run in the basement (a very nice
but humid vaulted cellar) At first thought I'd have to extend the
antenna cable to the next Window. But the long wave signal penetrated
very deep into that building so I found a proper place where I had
good reception :)

In the US I know that there are also similar kind of transmitters
available but I'm not sure about Australia (Where you are originated,
right?). I think nowadays the time is usually taken from GPS satelites
even though the receivers are much more complex.

I also had worked on another project where I decoded press images that
had been broadcast on long wave at that time. I had build up my own
receiver by tweaking a long wave radio to out-of-band frequency range
and I made a simple converter circuit which I attached to my 64. By
using that I was able to decode the pictures which was very exciting
for me because I did not know beforehand what signals these funny
beeping sounds where! So I analysed them and finaly found repetetive
seqeuences which turned out to build up pictures line by line. The 64
did not have enough memory to store one single pictures so I printed
them out on my 9-pin Dot-Matrix printer just as they came in. The
transmission of one picture took roughly 20-30 Minutes...

Unfortunately that service (intended for picture distribution of the
press images release by the major press agencies) was discontinued
when my project had reached a full functional level... So I would have
had to change to short wave reception of satelite images which I did
not do unfortunately.

Andi

From: Jonno Downes on 26 Jul 2010 18:30
Hi Andi

> Each clock puls is either 100ms or 300ms long representing a "1" or a
> "0" bit. So within one minute there are 60 bits which encode the time,
> date, daylight saving time status und other information (I think
> weather forcast AFAIR).

> For the 64 I had to attach the module to the user port (power supply +
> 1 data bit).

Is the last second (when the bit is 'not transmitted') used for
synching to the start of the next minute? If so, how do you get that
synch sygnal through 1 data bit?

> In the US I know that there are also similar kind of transmitters
> available but I'm not sure about Australia (Where you are originated,
> right?). I think nowadays the time is usually taken from GPS satelites
> even though the receivers are much more complex.

The only externally synched clocks I've seen here in Australia use GPS
or NTP

>
> I also had worked on another project where I decoded press images that
> had been broadcast on long wave at that time. I had build up my own
> receiver by tweaking a long wave radio to out-of-band frequency range
> and I made a simple converter circuit which I attached to my 64. By
> using that I was able to decode the pictures which was very exciting
> for me because I did not know beforehand what signals these funny
> beeping sounds where! So I analysed them and finaly found repetetive
> seqeuences which turned out to build up pictures line by line. The 64
> did not have enough memory to store one single pictures so I printed
> them out on my 9-pin Dot-Matrix printer just as they came in. The
> transmission of one picture took roughly 20-30 Minutes...
>

interesting! and interesting as well that (from the description) no
compression was being used? I would have thought that sort of
transmission would have been a perfect candidate for RLE?

Cheers

Jonno
 |  Next  |  Last
Pages: 1 2
Prev: PILOT cartridge (crt-file) for Commodore 64 (C64)
Next: Connecting Philips CM8833 monitor to C64